EUSKAL HERRIA DEELGUEZABAL: Homo sapiens sapiens species

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My critics of the Neanderthal species hypothesis I nterbreeding

with Homo sapiens in Europe.

Introduction

Currently, no complete karyotype analysis (chromosomal number, form, and size) has been reconstructed for Neanderthals due to the challenges in obtaining intact chromosomal structures from ancient DNA. However, insights have been drawn from genomic sequencing.

Neanderthals, would be a closely related group to Homo sapiens, and are presumed to have had the same

number of chromosomes: 46 (23 pairs),

This assumption is based on the genetic similarity between Neanderthals and modern humans, with Neanderthals sharing approximately 99.7–99.8% of their genome with Homo sapiens.

The total amount of DNA (in base pairs) in the genomes of Homo sapiens, Neanderthals, and species within the genus *Equus* (e.g., horses, donkeys, zebras) can be compared, although there are some differences in genome size and structure due to evolutionary divergence. Here's a breakdown:

---

### **1. Genome Sizes**

- **Homo sapiens (Modern Humans):**

- Genome Size: ~3.2 billion base pairs (~3,200,000 kilobases).

- Number of Genes: ~20,000–25,000 protein-coding genes.

- **Neanderthals (*Homo neanderthalensis*):**

- Genome Size: Nearly identical to modern humans, ~3.2 billion base pairs (~3,200,000 kilobases).

- Neanderthals share ~99.7–99.8% of their DNA with modern humans.

- Differences exist in specific alleles, with approximately 1–2% of Neanderthal DNA persisting in non-African modern human populations.

- **Equus Genus (Horses, Donkeys, Zebras):**

- Genome sizes vary slightly between species but are generally larger than humans:

- **Horse (*Equus caballus*):**

- Genome Size: ~2.7 billion base pairs (~2,700,000 kilobases).

- Number of Chromosomes: 64 (32 pairs).

- **Donkey (*Equus asinus*):**

- Genome Size: ~2.3 billion base pairs (~2,300,000 kilobases).

- Number of Chromosomes: 62 (31 pairs).

- **Zebra (e.g., *Equus grevyi* or *Equus quagga*):**

- Genome Size: ~2.4–2.5 billion base pairs (~2,400,000–2,500,000 kilobases).

- Number of Chromosomes: 32–46, depending on the species.

---

### **2. Genotypic Comparisons**

- **Homo sapiens vs. Neanderthals:**

- The genome sizes are essentially the same, but there are minor differences in genetic sequences.

- Neanderthal genomes include some distinct gene variants related to immune response, skin, and hair adaptations to cold climates.

- **Homo sapiens vs. Equus species:**

- While the overall genome size of horses is smaller than humans (~2.7 billion base pairs vs. ~3.2 billion base pairs), the gene number is similar (~20,000–25,000 genes).

- Horses and other Equus species have undergone significant chromosomal rearrangements compared to humans, leading to a different organization of their genomes.

---

### **3. Hybridization Insights**

- In *Equus* species (e.g., horses and donkeys), hybrids like mules (offspring of a horse and a donkey) are usually sterile due to chromosomal mismatches. This occurs because:

- Horses have 64 chromosomes, while donkeys have 62 chromosomes. Their hybrids end up with 63 chromosomes, which often disrupts gamete formation.

- Zebras, depending on the species, have even more chromosomal differences compared to horses and donkeys, making hybridization outcomes variable.

- In contrast, Homo sapiens and Neanderthals have highly similar chromosomal structures (46 chromosomes in both species) and genome sizes, facilitating successful interbreeding and fertile offspring.

---

### **Summary Table**

|--------------------------|-------------------------|-------------|--------------------------------------|

This comparison highlights that while genetic similarity facilitates interbreeding in humans and Neanderthals, chromosomal differences in *Equus* species create significant barriers to hybrid fertility.

For mammals, closely related species within a genus often have the same or similar numbers of chromosome pairs and genome sizes, which can serve as good examples of proximity and potential interbreeding. Here's an overview:

---

### **Key Characteristics for Potential Interbreeding**

- **Same Chromosome Number:** Closely matched chromosome numbers reduce barriers to hybrid fertility.

- **Similar Genome Size:** Similar amounts of DNA (measured in kilobases or megabases) often indicate genetic compatibility.

- **Shared Evolutionary History:** Recent common ancestors increase the likelihood of interbreeding.

---

### **Examples of Mammal Genera with Potential for Interbreeding**

#### **1. Genus *Canis* (Dogs, Wolves, Coyotes, Jackals)**

- **Chromosome Number:** All members of the genus *Canis* have 39 pairs of chromosomes (78 total).

- **Genome Size:** Similar genome sizes, around 2.4–2.5 billion base pairs (~2,400,000–2,500,000 kilobases).

- **Interbreeding:**

- Wolves (*Canis lupus*), dogs (*Canis lupus familiaris*), and coyotes (*Canis latrans*) can interbreed and produce fertile offspring.

- Hybrid examples include wolf-dog hybrids and coywolves (coyote-wolf hybrids).

- **Significance:** Demonstrates how chromosome and genome similarity facilitate fertile hybridization within a genus.

#### **2. Genus *Equus* (Horses, Donkeys, Zebras)**

- **Chromosome Number:**

- Horses (*Equus caballus*): 64 chromosomes (32 pairs).

- Donkeys (*Equus asinus*): 62 chromosomes (31 pairs).

- Zebras: 32–46 chromosomes, depending on the species.

- **Genome Size:** ~2.3–2.7 billion base pairs (~2,300,000–2,700,000 kilobases).

- **Interbreeding:**

- Hybrids like mules (horse-donkey) and zebroids (zebra-horse) are common but typically sterile due to mismatched chromosome numbers.

- Fertility decreases as chromosomal differences increase, making this genus a good example of partial compatibility.

#### **3. Genus *Pan* (Chimpanzees and Bonobos)**

- **Chromosome Number:** Both chimpanzees (*Pan troglodytes*) and bonobos (*Pan paniscus*) have 24 pairs of chromosomes (48 total).

- **Genome Size:** Very similar to humans and each other, ~3.0 billion base pairs (~3,000,000 kilobases).

- **Interbreeding:**

- Chimpanzees and bonobos can interbreed in captivity and produce fertile offspring.

- **Significance:** Closely related species in this genus highlight how chromosomal and genomic similarity can overcome hybridization barriers.

#### **4. Genus *Felis* (Domestic Cats and Wild Cats)**

- **Chromosome Number:** All members of the genus *Felis* have 19 pairs of chromosomes (38 total).

- **Genome Size:** Similar across the genus, ~2.5 billion base pairs (~2,500,000 kilobases).

- **Interbreeding:**

- Domestic cats (*Felis catus*) can interbreed with some wild cats, such as the African wildcat (*Felis lybica*), and produce fertile offspring.

- **Significance:** Demonstrates hybridization potential among species with identical chromosome numbers and genome sizes.

#### **5. Genus *Ursus* (Bears)**

- **Chromosome Number:** Most bears have 37 pairs of chromosomes (74 total).

- **Genome Size:** Similar across species, ~2.5–2.6 billion base pairs (~2,500,000–2,600,000 kilobases).

- **Interbreeding:**

- Grizzly bears (*Ursus arctos*) and polar bears (*Ursus maritimus*) interbreed in the wild, producing fertile hybrids known as "pizzly" or "grolar" bears.

- **Significance:** Illustrates how genetic compatibility and overlapping habitats enable natural hybridization.

---

### **Summary Table of Mammalian Genera**

|-------------|---------------------------------|------------------|-------------------|--------------------------------------|

| *Canis* | Dogs, Wolves, Coyotes | 39 | ~2,400,000 | Fertile hybrids (e.g., coywolves) |

| *Equus* | Horses, Donkeys, Zebras | 31–32 | ~2,300,000–2,700,000 | Sterile or partially fertile hybrids |

| *Pan* | Chimpanzees, Bonobos | 24 | ~3,000,000 | Fertile hybrids in captivity |

| *Felis* | Domestic and Wild Cats | 19 | ~2,500,000 | Fertile hybrids (e.g., hybrids with African wildcats) |

| *Ursus* | Grizzly and Polar Bears | 37 | ~2,500,000–2,600,000 | Fertile hybrids (e.g., pizzly bears) |

---

### **Conclusion**

The best examples of potential interbreeding involve genera like *Canis*, *Pan*, and *Ursus*, where chromosome numbers, genome sizes, and genetic proximity allow for fertile offspring. These cases demonstrate how genetic and chromosomal compatibility underpin hybridization potential, even between distinct species.

Analyzing the percentage of genetic commonalities and differences across biological kingdoms, animal clades, mammal families, primate genera, and *Homo* species requires looking at their shared genome sequences and conserved genes. Here's an overview with approximate percentages based on available studies, along with references for further exploration.

---

### **1. Biological Kingdoms**

#### **Genetic Commonalities Across Kingdoms**

- **Eukaryotes (Animals, Plants, Fungi, Protists):**

- Eukaryotic genomes share **~10–15%** of their genes, primarily involved in core cellular processes (e.g., DNA replication, transcription, translation).

- Example: Humans and yeast (*Saccharomyces cerevisiae*, Fungi) share ~23% of their genes.

- **Eukaryotes vs. Prokaryotes:**

- Core metabolic and replication genes are conserved, but shared genes drop to **~5–7%** between eukaryotes and bacteria.

- **References:**

- Koonin, E.V. (2003). "Comparative Genomics, Evolution, and the Origins of Cellular Functions."

- Lander et al. (2001). "Initial sequencing and analysis of the human genome."

---

### **2. Animal Clades**

#### **Genetic Commonalities Among Animal Phyla**

- **All Animals:**

- Animals share **~25–30%** of their genes, reflecting conserved developmental and structural pathways (e.g., Hox genes).

- Example: Humans and nematodes (*Caenorhabditis elegans*) share ~21% of their genome.

- **Vertebrates vs. Invertebrates:**

- Vertebrates (e.g., fish, amphibians, mammals) show higher genetic conservation among themselves (~65–80%) compared to invertebrates (~20–30%).

- **References:**

- Nematode Sequencing Consortium (1998). "Genome Sequence of the Nematode C. elegans."

- Searls, D.B. (2003). "Pharmacogenomics and Evolutionary Biology."

---

### **3. Mammal Families**

#### **Genetic Commonalities Among Mammals**

- **Mammals:**

- Mammals share **~85–95%** of their genes, with most differences arising from gene regulation and non-coding regions.

- Example: Humans and mice (*Mus musculus*) share ~85% of their genes.

- **References:**

- Mouse Genome Sequencing Consortium (2002). "Initial sequencing and comparative analysis of the mouse genome."

- Kumar et al. (2009). "Genomics and the Animal Kingdom."

---

### **4. Primate Genera**

#### **Genetic Commonalities Among Primates**

- **Primates:**

- Primates share **~98–99%** of their genome, depending on the lineage. Differences are largely in regulatory regions and non-coding DNA.

- Example:

- Humans and chimpanzees (*Pan troglodytes*): ~98.8% genetic similarity.

- Humans and gorillas (*Gorilla gorilla*): ~98%.

- Humans and orangutans (*Pongo pygmaeus*): ~96.9%.

- **References:**

- Varki et al. (2008). "The Chimpanzee Sequencing and Analysis Consortium."

- Locke et al. (2011). "Comparative and functional genomics of primates."

---

### **5. Homo Species**

#### **Genetic Commonalities Among *Homo* Species**

- **Homo sapiens vs. Neanderthals:**

- Neanderthals share **~99.7–99.8%** of their genome with modern humans.

- Example: The remaining differences involve immune system genes, adaptations to environment, and non-coding regulatory sequences.

- **Homo sapiens vs. Denisovans:**

- Denisovans share **~99.7%** of their genome with modern humans.

- **References:**

- Green et al. (2010). "A Draft Sequence of the Neandertal Genome."

- Reich et al. (2011). "Denisova Admixture and the Evolution of Modern Humans."

---

### **Summary Table**

|----------------------------|-------------------------|-------------------------------------------------|-------------------------------------|

| **Biological Kingdoms** | ~5–15% | Core cellular processes shared | Koonin (2003); Lander et al. (2001) |

| **Animal Clades** | ~20–80% | Higher in vertebrates; Hox genes conserved | Searls (2003); Nematode Sequencing Consortium (1998) |

| **Mammal Families** | ~85–95% | Humans and mice share ~85% | Mouse Genome Sequencing Consortium (2002) |

| **Primate Genera** | ~98–99% | Humans and chimps share ~98.8% | Varki et al. (2008); Locke et al. (2011) |

| **Homo Species** | ~99.7–99.8% | Neanderthals and Denisovans | Green et al. (2010); Reich et al. (2011) |

---

### **Conclusion**

Genetic similarity increases as we move from broad evolutionary groups (biological kingdoms) to closely related species (*Homo sapiens* and Neanderthals). These percentages illustrate the conservation of essential genes across life forms while highlighting the specificity of genetic differences that drive diversity.

The concept of "human races" as distinct biological categories has been largely debunked in modern genetics. Human genetic variation exists on a spectrum and correlates more strongly with geographic ancestry than with socially constructed racial categories. Here's an overview of the genetic similarities and differences among modern human populations, as determined by genome-wide studies:

---

### **1. Percentage of Genetic Similarity Among Humans**

- **Humans share ~99.9% of their genome across all populations** globally.

- This means that only about 0.1% of the genome varies among individuals.

- Most of this variation (~85–90%) exists within populations, while the remaining ~10–15% differentiates populations from different regions.

---

### **2. Sources of Genetic Variation**

- **Single-Nucleotide Polymorphisms (SNPs):**

- Most human genetic differences (~90%) are due to variations at single nucleotide positions (SNPs).

- These differences often correlate with geographic ancestry and migration history.

- **Structural Variants:**

- Differences in the number or arrangement of larger DNA segments also contribute to variation but to a lesser degree than SNPs.

---

### **3. Genetic Distance Between Populations**

- **Major Findings:**

- Genetic differences between populations from different continents are typically **~0.1–0.5%**.

- Examples:

- Genetic differences between populations in Europe and East Asia: ~0.1–0.15%.

- Genetic differences between populations in sub-Saharan Africa and other regions: ~0.3–0.5%, reflecting the greater genetic diversity in Africa due to the "Out of Africa" migration.

---

### **4. Patterns of Ancestral Genetic Markers**

- **Shared Ancestry:**

- Genetic heritage tests often identify markers associated with specific geographic regions. These markers represent probabilities, not definitive boundaries.

- Many markers are shared across regions due to historical migration, trade, and interbreeding.

- **Regional Differences:**

- Variants associated with traits like skin pigmentation, lactose tolerance, or disease resistance often differ by region.

- For example:

- *Lactase persistence* is more common in populations of European and some African ancestries.

- Genes linked to *sickle cell trait* occur more frequently in regions historically affected by malaria.

---

### **5. Practical Use of Ancestry Tests**

- Genetic tests (e.g., 23andMe, AncestryDNA) use SNP arrays to estimate proportions of ancestry from different regions.

- Example: A test may report a person as 50% European, 25% East Asian, and 25% sub-Saharan African based on statistical matching of SNPs to reference populations.

- These estimates rely on comparison with databases of people whose ancestry has been well-documented geographically.

---

### **Summary Table of Genetic Similarity**

| Level of Comparison | Genetic Similarity (%) | Notes |

|------------------------------|-------------------------|------------------------------------------------|

| **All Humans (Global)** | ~99.9% | Only ~0.1% variation between individuals. |

| **Populations within Continents** | ~99.85–99.9% | Most variation occurs within populations. |

| **Populations across Continents** | ~99.7–99.85% | Slightly greater variation due to migration and isolation. |

---

### **Conclusion**

Modern human populations are incredibly genetically similar, with only minor differences that correlate with geographic ancestry rather than distinct "races." These differences are small and gradual, and they reflect adaptations to local environments and historical migrations rather than discrete divisions. Genetic heritage tests exploit these subtle variations to estimate ancestral origins, but they underscore the shared genetic heritage of all humans.

Yes, *Homo sapiens*, *Homo neanderthalensis* (Neanderthals), and *Homo denisova* (Denisovans) share a common ancestor. Their evolutionary relationships can be outlined based on fossil evidence and genomic studies:

---

### **Shared Ancestor**

- The most recent common ancestor of these three groups is believed to be *Homo heidelbergensis*, which lived approximately **600,000–800,000 years ago**.

- *Homo heidelbergensis* is considered a transitional species that gave rise to multiple lineages:

- Neanderthals in Europe and western Asia.

- Denisovans in eastern Asia.

- Modern humans (*Homo sapiens*) in Africa.

---

### **Timeline and Divergence**

1. **~600,000–800,000 years ago:**

- The population of *Homo heidelbergensis* splits:

- One group remains in Africa and evolves into *Homo sapiens*.

- Another migrates to Eurasia and evolves into Neanderthals and Denisovans.

2. **~400,000–500,000 years ago:**

- The lineage leading to Neanderthals and Denisovans diverges from each other.

- Neanderthals occupy Europe and western Asia.

- Denisovans occupy parts of eastern Asia.

3. **~300,000–200,000 years ago:**

- Modern *Homo sapiens* begin to emerge in Africa.

4. **~50,000–70,000 years ago:**

- *Homo sapiens* leave Africa and interbreed with Neanderthals and Denisovans in Eurasia.

---

### **Evidence of Shared Ancestor**

1. **Fossil Evidence:**

- Fossils attributed to *Homo heidelbergensis* display a mix of traits seen in later Neanderthals, Denisovans, and modern humans.

- Sites include Sima de los Huesos (Spain), which shows traits intermediate between *Homo heidelbergensis* and Neanderthals.

2. **Genetic Evidence:**

- Genomic studies show that Neanderthals and Denisovans share more genetic similarities with each other than with modern humans, indicating a common Eurasian lineage.

- Modern humans share:

- ~1–2% of their DNA with Neanderthals (in non-African populations).

- ~4–6% of their DNA with Denisovans (in some populations, particularly in Oceania and Southeast Asia).

3. **Archaic Admixture:**

- Genetic data indicates gene flow between these groups after their divergence:

- Interbreeding between *Homo sapiens* and Neanderthals occurred in the Middle East and Europe.

- Interbreeding between *Homo sapiens* and Denisovans occurred in Asia and Oceania.

---

### **Conclusion**

*Homo sapiens*, *Homo neanderthalensis*, and *Homo denisova* share a common ancestor in *Homo heidelbergensis*. These three groups represent distinct evolutionary branches that occasionally interbred, leaving traces of Neanderthal and Denisovan DNA in modern human populations outside Africa. The evolutionary history of these species is a story of divergence, adaptation to different environments, and limited hybridization.

Speciation and extinction are central concepts in mammalian biology and evolutionary theory, as they explain the diversification of species and the loss of biodiversity over time. Here’s an overview of both concepts:

---

### **1. Speciation in Mammal Biology**

Speciation is the process by which new species arise. In mammals, this process can occur through various mechanisms influenced by genetics, behavior, ecology, and geography.

#### **Mechanisms of Speciation**

1. **Allopatric Speciation:**

- Occurs when populations are geographically isolated, preventing gene flow.

- Over time, genetic differences accumulate, leading to the emergence of distinct species.

- Example: Formation of distinct mammal species on islands (e.g., lemurs in Madagascar).

2. **Sympatric Speciation:**

- Happens within a single geographic area, often due to ecological or behavioral isolation.

- Example: Different feeding preferences or mating behaviors in rodents leading to reproductive isolation.

3. **Peripatric Speciation:**

- A small population becomes isolated at the edge of a larger population and evolves into a new species.

- Example: Isolated mammal populations in fragmented habitats.

4. **Parapatric Speciation:**

- Adjacent populations evolve into distinct species due to differing environmental pressures and limited gene flow.

- Example: Mammal species separated by a mountain range or river.

#### **Factors Driving Speciation in Mammals**

- **Geographical Barriers:** Mountains, rivers, and oceans can isolate populations.

- **Ecological Niches:** Competition and adaptation to specific niches encourage divergence.

- **Behavioral Differences:** Variations in mating calls, behaviors, or timing.

- **Genetic Drift and Mutation:** Especially in small populations, random genetic changes can drive speciation.

- **Natural Selection:** Adaptation to local environments leads to genetic divergence.

---

### **2. Extinction in Mammal Biology**

Extinction is the process by which a species ceases to exist. It is a natural part of evolution but has been accelerated in recent times by human activity.

#### **Types of Extinction**

1. **Background Extinction:**

- The natural, ongoing extinction rate of species due to environmental changes and competition.

- Example: Small mammal species that fail to adapt to climate shifts.

2. **Mass Extinction:**

- A rapid and widespread loss of species, often caused by catastrophic events.

- Example: Extinction of many mammal species during the end-Pleistocene megafaunal extinction (~10,000 years ago).

3. **Anthropogenic Extinction:**

- Caused by human activities such as habitat destruction, overhunting, and climate change.

- Example: Extinction of the Tasmanian tiger (*Thylacinus cynocephalus*).

#### **Causes of Extinction in Mammals**

- **Habitat Loss:** Deforestation, urbanization, and agriculture.

- **Climate Change:** Alters habitats and food availability.

- **Overexploitation:** Hunting, poaching, and fishing.

- **Invasive Species:** Competition or predation from non-native species.

- **Disease:** Outbreaks that can decimate populations.

---

### **3. Interplay Between Speciation and Extinction**

- **Biodiversity Balance:** Speciation adds new species to ecosystems, while extinction removes them.

- **Adaptive Radiation:** Following extinctions, surviving species may diversify rapidly, filling vacant ecological niches (e.g., mammal diversification after the dinosaur extinction).

- **Evolutionary Arms Race:** Predation, competition, and environmental changes drive both processes.

---

### **Examples in Mammalian History**

1. **Speciation Example:**

- Adaptive radiation of marsupials in Australia after geographic isolation.

- Evolution of diverse bat species due to niche specialization in feeding and echolocation.

2. **Extinction Example:**

- Extinction of mammoths and saber-toothed cats during the late Pleistocene.

- Current threats to mammals like the vaquita (*Phocoena sinus*), primarily due to human activity.

---

### **Conclusion**

Speciation and extinction are fundamental to understanding mammalian evolution. Speciation generates diversity through isolation and adaptation, while extinction highlights the vulnerability of species to environmental and anthropogenic pressures. Studying these processes provides insights into the history of life and informs conservation efforts to protect endangered mammal species.

The rate of speciation among primates varies depending on environmental, ecological, and genetic factors. While specific rates are challenging to determine precisely, estimates based on fossil records, molecular clock data, and comparative genomics provide approximate timelines. Here's an analysis of speciation rates in terms of thousands of years for primate families, genera, and species:

---

### **1. General Primate Speciation Rates**

- **Overall Rate:**

- Primates typically show a speciation rate of **1 new species every 1–2 million years**.

- This rate is slower than in some other mammal groups due to their longer lifespans, generation times, and dependency on stable habitats like forests.

---

### **2. Rate of Speciation by Primate Family**

#### **Hominidae (Great Apes, Including Humans)**

- Speciation Rate: **~1 species every 1–2 million years**.

- Example:

- Divergence of *Homo sapiens* from *Homo heidelbergensis*: ~300,000–600,000 years ago.

- Divergence of the chimpanzee (*Pan troglodytes*) and human lineages: ~5–7 million years ago.

#### **Cercopithecidae (Old World Monkeys)**

- Speciation Rate: **~1 species every 1–3 million years**.

- Example:

- Divergence of colobine monkeys (*Colobus* species) from cercopithecines (baboons and macaques): ~10 million years ago.

- Radiation of macaques (*Macaca* species) into diverse lineages: ~5 million years ago.

#### **Callitrichidae (Marmosets and Tamarins)**

- Speciation Rate: **~1 species every 500,000–1 million years**.

- Example:

- Rapid diversification in South America due to ecological opportunities and forest fragmentation.

#### **Atelidae (Howler Monkeys, Spider Monkeys)**

- Speciation Rate: **~1 species every 1–2 million years**.

- Example:

- Divergence of howler monkeys (*Alouatta* species) from other atelids: ~10–12 million years ago.

---

### **3. Speciation Rates in Primate Genera**

#### **Homo (Humans and Close Relatives)**

- Speciation Rate: **~1 species every 300,000–600,000 years** during the last 2 million years.

- Example:

- *Homo sapiens* divergence from Neanderthals and Denisovans: ~500,000 years ago.

#### **Macaca (Macaques)**

- Speciation Rate: **~1 species every 1 million years**.

- Example:

- Macaque species are highly adaptive, leading to a moderate speciation rate.

#### **Lemuridae (Lemurs)**

- Speciation Rate: **~1 species every 300,000–1 million years** in isolated environments like Madagascar.

- Example:

- Adaptive radiation of lemurs following Madagascar's separation from Africa (~60 million years ago).

---

### **4. Fast vs. Slow Speciation Rates**

- **Faster Rates (~300,000–1 million years):**

- Occur in environments with strong ecological pressures or isolation, such as:

- Madagascar (lemurs).

- South American rainforests (marmosets and tamarins).

- **Slower Rates (~1–3 million years):**

- Seen in stable environments with longer-lived species and fewer ecological pressures, such as:

- Great apes (*Hominidae*).

---

### **Factors Influencing Primate Speciation Rates**

1. **Habitat Stability:**

- Stable environments (e.g., tropical forests) often result in slower speciation.

- Fragmented or changing habitats (e.g., during climatic shifts) can accelerate speciation.

2. **Reproductive Isolation:**

- Geographical barriers (rivers, mountains) are critical for isolating populations and driving divergence.

3. **Ecological Niches:**

- Niche specialization, such as dietary preferences, drives adaptive radiation in some genera.

4. **Generation Time:**

- Longer generation times in great apes slow the accumulation of genetic differences.

---

### **Conclusion**

Speciation rates among primates typically range from **1 new species per 300,000–3 million years**, depending on the family, genus, and environmental conditions. Rapid speciation is observed in isolated or ecologically dynamic regions, while slower rates are seen in stable habitats with longer-lived species.

Homo neanderthalensis (Neanderthals):

Origin: Neanderthals emerged in Eurasia around 400,000 to 200,000 years ago during the Middle Pleistocene.

Geographical Distribution: They inhabited a wide range of environments, from Western Europe to Central Asia, and from the Middle East to as far as Siberia.

Palaeolithic Period: Neanderthals lived during the Palaeolithic period, characterised by the use of stone tools and a hunter-gatherer lifestyle. They adapted to various climates, including colder regions during glacial periods.

Ice Ages: Neanderthals experienced multiple ice ages, adapting to the challenges of cold climates. They were well-adapted to the cold and are believed to have used clothing and controlled fire for warmth.

Cultural Complexity: Neanderthals exhibited cultural complexity, creating tools, using symbolism, and burying their dead with rituals. They had a diverse toolkit, including Mousterian tools.

Interaction with Homo sapiens: There is evidence of interaction between Neanderthals and Homo sapiens, possibly including interbreeding. Neanderthals coexisted with early Homo sapiens in Eurasia.

Transitional Periods:

Neolithic Period: Neanderthals were not directly involved in the Neolithic Revolution, marked by the transition to agriculture and settled communities. This shift primarily occurred among Homo sapiens.

Bronze Age, Iron Age, Copper Age: Neanderthals did not experience these ages as they predated these technological advancements. These ages are associated with Homo sapiens and their development of metallurgy, agriculture, and complex societies.

Homo Denisoviensis:

Discovery: Homo denisoviensis is known from Denisova Cave in Siberia. The existence of this hominin was identified through DNA analysis of fossils found in the cave.

Genetic Legacy: Denisovans interbred with both Neanderthals and Homo sapiens, leaving traces of their DNA in the genomes of some modern human populations, especially in Asia and Oceania.

Decline of Neanderthals:

Climax Domination: Neanderthals reached their peak during the last glacial maximum around 20,000 to 30,000 years ago when ice sheets covered large parts of Europe and Asia.

Decline and Extinction: Neanderthals eventually declined and went extinct around 40,000 years ago. The exact reasons for their decline are debated and may involve a combination of factors, including climate change, competition with Homo sapiens, and possibly cultural and technological differences

------------

Evidence of interbreeding between Homo sapiens (modern humans) and Homo neanderthalensis (Neanderthals) comes from the analysis of ancient DNA extracted from fossilized remains. The most significant evidence comes from the sequencing of Neanderthal genomes, which has provided insights into the genetic relationship between the two species.

Genomic Studies:

In 2010, the Max Planck Institute for Evolutionary Anthropology successfully sequenced the Neanderthal genome using DNA extracted from a toe bone found in the Denisova Cave in Siberia. The analysis revealed that non-African modern humans share about 1-2% of their DNA with Neanderthals, indicating interbreeding between the two populations.

Human-Neanderthal Hybrid Specimens:

Some fossil specimens also show characteristics that suggest a mix of Neanderthal and modern human features. For example, a specimen called the Oase 1 mandible, found in Romania, is considered a human-Neanderthal hybrid based on its combination of anatomical features.

Denisovan Interbreeding:

In addition to Neanderthals, evidence has emerged of interbreeding between modern humans and another archaic human group called Denisovans. The Denisovan genome was also sequenced from a finger bone found in the Denisova Cave. Modern human populations in Oceania and parts of Asia have been found to carry Denisovan DNA.

Distribution of Neanderthal DNA in Modern Humans:

The Neanderthal DNA in modern humans is not uniformly distributed. Certain populations carry more Neanderthal genetic material than others. This suggests that interbreeding events occurred at different times and places.

These pieces of evidence collectively support the idea that Homo sapiens and Homo neanderthalensis interbred, leading to a small but significant contribution of Neanderthal DNA in the modern human gene pool. The study of ancient DNA has opened a window into the complex interactions and relationships between different hominin species in the past.

.... generally understood that non-African modern humans share a small percentage of their DNA with Neanderthals, suggesting some interbreeding between the two populations.

The percentage of Neanderthal DNA in modern Europeans is estimated to be around 1-2% on average. However, these percentages can vary among individuals. Some may have higher or lower percentages, and certain populations may exhibit slightly different levels of Neanderthal ancestry.

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The concept of biological species is a fundamental idea in biology, and it refers to a group of organisms that can interbreed and produce fertile offspring under natural conditions. In mammals, including humans, the concept of a species is typically based on reproductive compatibility. Here are some key terms related to this concept:

Biological Species:

A group of individuals that can interbreed and produce fertile offspring under natural conditions.

Members of the same species share common characteristics and genetic traits.

Fertility:

Fertility in mammals refers to the ability of an organism to produce viable and fertile offspring.

A fertile individual is capable of successfully reproducing and passing on its genes to the next generation.

Fecundity:

Fecundity refers to the potential reproductive capacity of an organism, often measured by the number of offspring an individual can produce in a given period.

It is important to note that fecundity does not guarantee successful reproduction, as factors such as environmental conditions, availability of resources, and mate availability also play crucial roles.

Hybrids:

Hybrids are the offspring resulting from the mating of individuals from different species or subspecies.

While some hybrids may be viable and fertile, many are sterile, meaning they cannot produce offspring. Even if hybrids are fertile, they may have reduced fertility compared to individuals within the parent species.

In mammals, including humans, the concept of species is often more straightforward due to the limited occurrence of hybridization between different species. However, it's essential to recognize that reproductive isolation is a key factor in maintaining distinct biological species. Barriers to reproduction can be prezygotic (occurring before fertilization) or postzygotic (occurring after fertilization), and they contribute to the prevention of gene flow between distinct species.

Understanding the concepts of fertility, fecundity, and hybrids is crucial for comprehending the dynamics of populations, the formation of new species, and the broader field of reproductive biology

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It's important to approach the topic of genetic differences among human populations with sensitivity and a recognition of the shared genetic heritage of all human beings. Genetic variation exists among individuals and populations, but it's crucial to understand that the concept of "race" does not have a strict genetic basis. There is more genetic diversity within so-called racial groups than between them.

Genetic Variation:

Genetic variation exists in all human populations, and it is a result of both historical and environmental factors.

The Human Genome Project has shown that humans share approximately 99.9% of their DNA, emphasizing the common ancestry of the human species.

Population Genetics:

Genetic differences among populations can be observed due to factors such as historical migrations, genetic drift, and natural selection.

Genetic variation is distributed continuously across geographical regions rather than being confined to specific racial categories.

Geographical Patterns:

Some genetic variations may show geographical patterns due to historical migration and settlement patterns.

However, these patterns are complex, and it's not accurate to assign specific genetic traits exclusively to one racial or ethnic group.

Chromosomal Variation:

The human genome consists of 23 pairs of chromosomes, and while there may be variations in allele frequencies among different populations, it is essential to recognize the overall genetic similarity.

Chromosomes do not have exclusive loci that define a particular racial or ethnic group.

Population-Specific Alleles:

Certain alleles or genetic variants may be more prevalent in specific populations due to historical factors and selective pressures.

However, these alleles are not exclusive to any one population.

Admixture:

Many populations are the result of historical admixture between different groups, further blurring any clear genetic boundaries.

Admixture is common, especially in regions where different populations have historically come into contact.

It's crucial to approach discussions about genetic diversity with caution and to avoid reinforcing outdated and scientifically unsupported concepts of race. The focus should be on the rich diversity of human populations and the shared genetic heritage that unites us. Genetic studies consistently emphasize the importance of individual variation and the interconnectedness of all human populations.

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Concept of biological species in mammals, fertility, fecundity, hybrids.

Biological Species:

A group of individuals that can interbreed and produce fertile offspring under natural conditions.

Members of the same species share common characteristics and genetic traits.

Fertility:

Fertility in mammals refers to the ability of an organism to produce viable and fertile offspring.

A fertile individual is capable of successfully reproducing and passing on its genes to the next generation.

Fecundity:

Fecundity refers to the potential reproductive capacity of an organism, often measured by the number of offspring an individual can produce in a given period.

Hybrids:

Hybrids are the offspring resulting from the mating of individuals from different species or subspecies.

Genetic differences between human races or biotypes, Asian, African, amerindians, European, genes, DNA kb percentage of differences, chromosomes with more loci adding variance and diversity y human genome among continents.

The concept of "race" in humans is a complex and controversial topic, especially when discussing genetic differences. The genetic variation among human populations does exist, but it's important to approach the topic with sensitivity and understanding of the scientific consensus.

Genetic Differences Between Human Populations:

Human populations exhibit genetic variation that has been shaped by historical, geographic, and environmental factors.

Genetic differences between populations are a result of factors such as genetic drift, natural selection, migration, and demographic history.

Human Genome Variation:

The human genome is remarkably similar across different populations. Studies have shown that over 99.9% of the human genome is shared among all individuals, regardless of their geographic ancestry.

Most genetic variation occurs within populations rather than between them. This means that individuals within the same population can be more genetically diverse than individuals from different populations.

DNA Variation Across Continents:

While there are genetic differences between populations, the majority of genetic variation occurs within populations rather than between them.

Research has shown that the genetic variation observed within continental populations (e.g., within Africa, Europe, Asia, etc.) is often greater than the genetic variation observed between continental populations.

This means that individuals from different continents may share more genetic similarities with each other than with individuals from their own continent.

Chromosomal Variation:

Variation in the human genome is distributed across all chromosomes, and there is no single chromosome that contains all the genetic differences between populations.

Certain regions of the genome may show higher levels of genetic diversity or variation due to factors such as natural selection, recombination rates, and historical population dynamics.

Population Genetics Studies:

Population genetics studies have shown that while there are genetic differences between populations, these differences do not neatly correspond to traditional notions of race or continental ancestry.

Genetic variation within populations often overlaps with genetic variation found in other populations, making it difficult to categorize individuals into discrete racial or continental groups based solely on genetic data.

In summary, while genetic differences do exist among human populations, the majority of genetic variation occurs within populations rather than between them. The concept of race is a social construct that does not have a clear genetic basis, and it's important to approach discussions about human genetic diversity with caution and respect for the complexities involved.

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Genetic origin tests, often conducted through DNA analysis from mouth epithelium or saliva samples, aim to provide individuals with information about their ancestral origins based on genetic markers. These tests can analyze genetic variations known as single nucleotide polymorphisms (SNPs) across the genome to infer ancestral origins. Here are some potential outputs in terms of origin categories that such tests might provide:

Sub-Saharan African Ancestry:

This category typically includes individuals with genetic markers associated with populations from sub-Saharan Africa. It encompasses a wide range of ethnic groups and cultures across the African continent.

Semitic or Middle Eastern Ancestry:

Individuals with genetic markers associated with populations from the Middle East or regions historically inhabited by Semitic-speaking peoples might fall into this category.

Asian Ancestry:

This category may encompass individuals with genetic markers associated with populations from East Asia, South Asia, Southeast Asia, or Central Asia.

Arabic Ancestry:

This category may refer to individuals with genetic markers associated with populations from the Arab world, including regions such as the Arabian Peninsula, North Africa, and parts of the Levant.

European Ancestry:

Individuals with genetic markers associated with populations from Europe may fall into this category. It includes diverse ethnic groups and populations across the European continent.

Native American Ancestry:

Some tests may also identify individuals with genetic markers associated with indigenous populations of the Americas, including North, Central, and South America.

Oceanian Ancestry:

This category may include individuals with genetic markers associated with populations from the Pacific Islands and other regions of Oceania.

It's important to note that the specific categories provided by genetic origin tests may vary depending on the company or laboratory conducting the analysis. Additionally, these tests provide estimates of ancestry based on genetic data and population reference databases, and they may not capture the full complexity of an individual's ancestral background. An individual's actual ancestry may be more diverse and nuanced than what is reflected in the test result

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The Max Planck Institute for Evolutionary Anthropology, among other institutions, has been involved in research related to Neanderthals, human evolution, and population genetics. They have contributed to our understanding of the interbreeding between Homo sapiens (modern humans) and Neanderthals, as evidenced by genetic studies showing Neanderthal DNA in the genomes of non-African modern human populations.

The hypothesis regarding the Neanderthal human species and the origin of Nordic Europeans has been an area of interest and research in anthropology and genetics. The Max Planck Institute for Evolutionary Anthropology, among other institutions, has contributed significantly to our understanding of human evolution and population history.

One aspect of this hypothesis suggests that there may have been interbreeding between Neanderthals and anatomically modern humans (Homo sapiens) when they came into contact in Europe tens of thousands of years ago. This interbreeding might have resulted in the incorporation of Neanderthal DNA into the genomes of modern humans, including those of populations in Europe.

Genetic studies have indeed shown that non-African populations, including Europeans, carry traces of Neanderthal DNA in their genomes. These findings suggest that there were indeed interactions between Neanderthals and early modern humans as they migrated into Europe.

As for the specific origin of Nordic Europeans, it's important to note that the population history of Europe is complex and involves multiple waves of migration, interaction, and adaptation over tens of thousands of years. While Neanderthal DNA might be one component of the genetic makeup of modern Europeans, the broader genetic landscape of Nordic Europeans, like other European populations, is shaped by various factors including subsequent migrations, cultural exchanges, and evolutionary processes.

Research in this field continues to refine our understanding of the relationships between different human populations and the factors that have shaped the genetic diversity we observe today. While the Max Planck Institute and other research institutions have made significant contributions to this area of study, it's an ongoing and evolving field with new insights emerging from interdisciplinary research efforts.

Modern Europeans have a diverse genetic background shaped by various historical events, including migrations, invasions, and trade. European populations have genetic contributions from different regions, including Africa, the Middle East, and Asia.

Population genetics research has identified certain genetic markers and patterns that can provide insights into human migration and population movements

In biology, the concept of species is fundamental to the classification and understanding of living organisms. A species is generally defined as a group of organisms that can interbreed and produce fertile offspring in nature. This concept is known as the Biological Species Concept and was proposed by Ernst Mayr in 1942.

Key points regarding the concept of species in biology include:

Reproductive Compatibility: Members of the same species are capable of mating and producing viable offspring. This reproductive compatibility ensures genetic continuity within the species.

Genetic Similarity: Members of the same species share a significant degree of genetic similarity. Although there can be variations within a species, the genetic differences among individuals of the same species are typically smaller than the differences between individuals of different species.

Distinctiveness: Species are distinct units of biodiversity. They are characterized by unique combinations of traits, behaviors, and adaptations that distinguish them from other species.

Evolutionary Independence: Species are considered as independent evolutionary units. They evolve separately from other species, accumulating genetic changes over time through mechanisms such as natural selection, genetic drift, and mutation.

Reproductive Isolation: Species are reproductively isolated from each other, meaning that they do not interbreed with individuals from other species under natural conditions. This reproductive isolation can be due to geographical, ecological, behavioral, or genetic barriers.

Species Naming and Classification: Taxonomists classify species based on shared characteristics and evolutionary relationships. Each species is given a unique scientific name consisting of two parts: the genus and the specific epithet. For example, in Homo sapiens, "Homo" is the genus and "sapiens" is the specific epithet.

Species Diversity: Earth is home to a vast array of species, ranging from microscopic bacteria to towering trees and complex animals. Species diversity is essential for ecosystem functioning and provides a basis for various ecological processes.

It's important to note that while the Biological Species Concept is widely used, there are other species concepts as well, each with its own criteria and limitations. These include the Morphological Species Concept, the Ecological Species Concept, the Phylogenetic Species Concept, and others. The choice of species concept often depends on the specific research question or context.

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Let's apply the concepts of population genetics—represented by alleles Q, P, R, and S—to the reproductive biology and reproductive ecology of a single mammal species, such as the Eastern gray squirrel (Sciurus carolinensis).

Allele Frequencies (p, q, r, s):

In a population of Eastern gray squirrels, let's say allele Q represents a gene variant for a trait related to foraging behavior, allele P represents a gene variant for fur color, allele R represents a gene variant for body size, and allele S represents a gene variant for reproductive timing.

The frequencies of these alleles (p, q, r, s) in the population would represent the proportion of individuals carrying each variant within the population.

For example, if 70% of squirrels carry allele Q for foraging behavior, then the frequency of allele Q (q) would be 0.70, and the frequency of allele q would be 0.30.

Genotype Frequencies:

Genotype frequencies represent the proportion of individuals with different combinations of alleles within the population.

For example, if the population is in Hardy-Weinberg equilibrium, we can predict the frequencies of different genotypes based on allele frequencies. For instance, for a single locus with two alleles (Q and q), the genotype frequencies would be determined by the Hardy-Weinberg equation: p^2 + 2pq + q^2 = 1.

Natural Selection:

In the Eastern gray squirrel population, certain alleles may confer advantages or disadvantages in terms of survival and reproduction.

For instance, allele R for larger body size might provide an advantage in competition for resources or in predator avoidance.

Natural selection would act on these alleles, potentially increasing the frequency of advantageous alleles (like R) and decreasing the frequency of disadvantageous alleles.

Genetic Drift:

Genetic drift refers to random changes in allele frequencies over time due to chance events.

In a small isolated population of Eastern gray squirrels, genetic drift might play a significant role, leading to fluctuations in allele frequencies even in the absence of natural selection.

This could result in the fixation of certain alleles (where one allele becomes the only variant present) or the loss of others.

Gene Flow:

Gene flow occurs when individuals from one population migrate and breed with individuals from another population, leading to the exchange of alleles between populations.

In the case of Eastern gray squirrels, gene flow between different populations could result in the spread of advantageous alleles or the introduction of novel alleles into a population.

By considering these concepts of population genetics in the context of reproductive biology and reproductive ecology, we can gain insights into the genetic dynamics of a single mammal species like the Eastern gray squirrel. These dynamics play a crucial role in shaping the genetic diversity and adaptation of populations over time.

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Let's apply the concepts of population genetics—represented by the variables q, p, r, and s—to the reproductive biology and reproductive ecology of a single mammal species, such as the common gray wolf (Canis lupus).

q: Allele frequency of a recessive allele affecting a reproductive trait.

In the gray wolf population, let's say there's a recessive allele (q) responsible for coat color variation. Wolves with this allele might have a different camouflage advantage in certain habitats, affecting their reproductive success.

p: Allele frequency of a dominant allele affecting a reproductive trait.

Another allele (p) could represent a dominant gene for jaw strength. Wolves with this allele might have an advantage in hunting, leading to increased access to food resources and ultimately higher reproductive success.

r: Selection coefficient against individuals with certain reproductive traits.

The selection coefficient (r) against individuals with genetic diseases like hip dysplasia might influence the reproductive success of affected individuals. Wolves with severe hip dysplasia might have difficulty hunting or moving, reducing their likelihood of reproducing.

s: Selection coefficient against individuals with certain reproductive strategies.

The selection coefficient (s) could represent competition for mates within a wolf pack. Wolves with more aggressive or dominant behaviors (e.g., alpha males) might have higher reproductive success compared to subordinate individuals, influencing the distribution of alleles associated with reproductive behavior in the population.

By understanding these population genetics concepts within the context of reproductive biology and ecology in gray wolves, researchers can gain insights into how genetic variation, natural selection, and reproductive strategies interact to shape the dynamics of wolf populations. This knowledge is crucial for conservation efforts and managing the genetic health and diversity of wild populations.

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The percentage of genetic similarity between Homo sapiens and other organisms varies depending on the specific species being compared and the method of measurement used. However, I can provide some general estimates based on available scientific knowledge:

Other Hominins:

Neanderthals: Studies estimate that modern humans share about 1-2% of their DNA with Neanderthals, indicating interbreeding between the two species when they coexisted.

Denisovans: Modern humans also share genetic material with Denisovans, with estimates suggesting around 1-2% of DNA shared between modern humans and Denisovans.

Other Mammals:

Chimps and Bonobos: Homo sapiens shares about 98-99% of its DNA with chimpanzees and bonobos, which are our closest living relatives among mammals.

Other mammalian species will have lower percentages of genetic similarity, with decreasing similarity as evolutionary distance increases.

Other Vertebrates:

Vertebrates, such as mice and rats, share a smaller percentage of genetic similarity with humans compared to other mammals, likely around 85-90%.

Fish, amphibians, and reptiles would have even lower percentages of genetic similarity, often below 80%.

Other Animals:

Invertebrates, such as insects, share even less genetic similarity with humans, typically less than 50%.

Genetic similarity decreases further when comparing humans to more distantly related organisms like fungi or plants.

Other Biological Species:

Comparing humans to organisms outside the animal kingdom, such as bacteria or archaea, reveals even lower levels of genetic similarity, often less than 20%.

It's important to note that these percentages are rough estimates and can vary depending on the specific genetic regions being compared and the methods used for analysis. Additionally, genetic similarity does not necessarily correlate directly with evolutionary relatedness, as some genetic regions may be more conserved across species than others

Determining the percentage of genetic similarity between different species can be complex and varies depending on the specific genes or regions of the genome being compared, as well as the methods used for analysis. However, I can provide some general estimates based on available scientific knowledge as of my last update in January 2022:

Between Homo sapiens and other hominins (e.g., Neanderthals, Denisovans):

Studies suggest that modern humans share approximately 1-2% of their DNA with Neanderthals and Denisovans. This indicates that Homo sapiens interbred with these other hominin species during prehistoric times.

Between Homo sapiens and other mammals:

The genetic similarity between humans and other mammals varies widely depending on the species being compared. For example, humans share a significant portion of their genome with primates, such as chimpanzees, with estimates ranging from 95-98% similarity.

Between Homo sapiens and other vertebrates:

Humans share a common ancestor with other vertebrates, including mammals, birds, reptiles, amphibians, and fish. The percentage of genetic similarity decreases as evolutionary distance increases. For example, humans share fewer genes in common with birds or reptiles compared to mammals.

Between Homo sapiens and other animals:

The percentage of genetic similarity between humans and other animals varies widely depending on the specific species. For example, humans share a relatively high degree of genetic similarity with other primates, such as chimpanzees and gorillas, due to shared ancestry. However, the genetic similarity decreases when comparing humans to more distantly related animals, such as insects or mollusks.

Between Homo sapiens and other biological species:

Genetic similarity between humans and other biological species depends on their evolutionary relationships. Closer relatives, such as other primates, share more genetic similarities with humans compared to more distantly related species. Across the entire spectrum of life, genetic similarity diminishes as evolutionary distance increases.

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The statement that genetic transfer is impossible among different species of the same genus is not entirely accurate. While interspecies gene transfer between distinct species is generally less common compared to gene transfer within the same species or between closely related species, it is not impossible and has been observed in various forms in nature. Here are a few examples:

Horizontal Gene Transfer (HGT): Horizontal gene transfer refers to the transfer of genetic material between organisms that are not directly related by descent. While HGT is more commonly observed in bacteria and archaea, there is evidence to suggest that it can also occur between different species of eukaryotes. For example, there have been instances of HGT between plants and fungi, as well as between plants and bacteria.

Endosymbiosis: Endosymbiosis is a process in which one organism lives inside another organism. It has played a significant role in the evolution of eukaryotic organisms, particularly through the establishment of organelles such as mitochondria and chloroplasts. Endosymbiotic events involve the transfer of genetic material between different species. For instance, the origin of mitochondria is believed to have involved an endosymbiotic event between a bacterial cell and a primitive eukaryotic cell.

Hybridization and Introgression: Hybridization occurs when individuals from two different species mate and produce offspring. While hybrids are typically infertile, in some cases, they may backcross with one of the parent species, resulting in introgression—the transfer of genetic material from one species to another. This process is particularly common in plants and can also occur in animals.

Viral Vectors and Gene Transfer: Viruses can serve as vectors for the transfer of genetic material between different species. Viruses can infect host cells and integrate their genetic material into the host genome. In some cases, this genetic material may be transferred horizontally between individuals of different species, facilitating gene flow between them.

While interspecies gene transfer is not as common as intraspecies gene transfer, it does occur and can contribute to genetic diversity and evolutionary innovation. Therefore, it would be inaccurate to state that genetic transfer among different species of the same genus is impossible, as there are mechanisms through which genetic material can be exchanged between organisms of different species.

It is not accurate to claim that genetic transfer is impossible among different species of the same genus. In fact, genetic transfer can and does occur between species within the same genus, albeit less frequently than within the same species. The extent and frequency of genetic transfer depend on various factors, including genetic compatibility, ecological factors, and evolutionary relationships.

Horizontal gene transfer (HGT) and hybridization are two mechanisms through which genetic material can be exchanged between different species within the same genus:

Horizontal Gene Transfer (HGT): HGT involves the transfer of genetic material between different organisms, often of different species. While HGT is more commonly associated with bacteria and other single-celled organisms, it can also occur in multicellular organisms. In some cases, genes can be transferred horizontally between closely related species within the same genus, especially if they share similar habitats or ecological niches.

Hybridization: Hybridization occurs when individuals from different species within the same genus interbreed and produce viable offspring. While hybridization is more common within the same species, it can also occur between closely related species within the same genus under certain conditions. Hybridization can lead to the exchange of genetic material between species and the formation of hybrid individuals with unique genetic combinations.

Examples of genetic transfer between species within the same genus are found in various groups of organisms, including plants, animals, and fungi. For instance:

In plants, hybridization between different species within the same genus is well-documented, leading to the formation of hybrid species with intermediate traits.

In animals, cases of hybridization between closely related species within the same genus have been observed, resulting in fertile hybrid offspring.

In fungi, horizontal gene transfer has been reported between different species within the same genus, contributing to genetic diversity and adaptation.

While genetic transfer between species within the same genus is possible, it may not always result in successful gene flow or the establishment of stable hybrid populations. Factors such as reproductive isolation, genetic compatibility, and ecological constraints can influence the outcome of genetic transfer events between species.

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In some cases, hybrid specimens resulting from interbreeding between two species of the same genus may indeed exhibit reduced fertility or infertility. This phenomenon is commonly observed and is known as hybrid infertility or hybrid sterility. Here's why it can occur:

Genetic Incompatibility: Even though two species may be closely related within the same genus, they may have evolved genetic differences that affect the fertility of hybrids. These genetic incompatibilities can manifest in various ways, such as disruptions in meiosis, gamete development, or embryo development.

Mismatched Chromosome Number or Structure: Hybrids often inherit chromosomes from both parent species, which can lead to mismatches in chromosome number or structure. These chromosomal abnormalities can disrupt normal meiosis, leading to the production of gametes with an incorrect number of chromosomes or inviable gametes.

Hybrid Breakdown: Sometimes, hybrids may be initially fertile, but their offspring (F2 generation and beyond) may exhibit reduced fertility or infertility. This phenomenon, known as hybrid breakdown, can occur due to the accumulation of deleterious genetic interactions over successive generations.

Reproductive Isolation Mechanisms: Species within the same genus may have evolved mechanisms to prevent hybridization and maintain reproductive isolation. These mechanisms can include differences in mating behaviors, flowering times, or physiological barriers to fertilization.

Evolutionary Divergence: Despite their genetic similarities, species within the same genus may have undergone divergent evolutionary paths, leading to differences in reproductive biology, developmental processes, or genomic organization. These differences can contribute to hybrid infertility.

Examples of hybrid infertility between species of the same genus are observed in various organisms, including plants, animals, and fungi. For instance, in plants, hybrid infertility is often observed in interspecific crosses due to genetic incompatibilities affecting pollen viability, seed development, or embryo growth.

Overall, hybrid infertility between species of the same genus is a common phenomenon that reflects the complex interactions between genetic, developmental, and evolutionary factors. It underscores the importance of reproductive isolation mechanisms in maintaining species boundaries and preserving genetic integrity within populations.

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The karyotype of Homo neanderthalensis, commonly known as Neanderthals, is not as precisely known as that of modern humans (Homo sapiens) due to the lack of intact Neanderthal chromosomes. However, researchers have made inferences about Neanderthal karyotypes based on the analysis of Neanderthal DNA extracted from fossil remains.

Based on available genomic data, it is estimated that Neanderthals had a diploid chromosome number (2n) similar to that of modern humans, which is 46 chromosomes. This means that Neanderthals, like humans, likely had 23 pairs of chromosomes.

Studies analyzing Neanderthal DNA have provided insights into specific chromosomal regions and genetic variations between Neanderthals and modern humans. These studies have identified genetic differences, including nucleotide substitutions, insertions, deletions, and structural variations, which have helped researchers understand the genetic relationship between Neanderthals and modern humans.

While the exact karyotype of Neanderthals remains speculative, ongoing research in paleogenetics and ancient DNA analysis continues to shed light on the genomic makeup and evolutionary history of Neanderthals and their relationship to modern humans.

Homo ergaster is an extinct species of early Homo, believed to have lived in Africa during the Early Pleistocene, approximately 1.8 to 1.3 million years ago. As such, there are no direct karyotype data available for Homo ergaster because karyotyping, which involves analyzing the number, size, and shape of chromosomes in a cell, requires intact chromosome samples.

However, scientists have inferred certain aspects of the karyotype of Homo ergaster based on comparative genomics and studies of related hominin species, such as Homo sapiens and other early Homo species like Homo habilis and Homo erectus.

Based on evolutionary relationships and anatomical similarities, it is generally assumed that Homo ergaster had a karyotype similar to that of other early Homo species, likely consisting of 46 chromosomes. This chromosome number is consistent with the karyotype of modern humans (Homo sapiens) and other great apes, such as chimpanzees and gorillas.

While the overall chromosome number is likely similar to that of modern humans, there may have been variations in the structure and organization of specific chromosomes, as well as differences in the sequences of individual genes. However, without direct fossil evidence or preserved chromosome samples, it is challenging to provide precise details about the karyotype of Homo ergaster.

Studies of ancient DNA and comparative genomics have provided valuable insights into the genetic relationships between different hominin species, but these methods have limitations in reconstructing detailed karyotypic information. Therefore, the exact karyotype of Homo ergaster remains speculative, and further research may provide additional insights into the chromosomal characteristics of this early human ancestor.

The karyotype of Homo habilis, an extinct species of the genus Homo believed to have lived approximately 2.1 to 1.5 million years ago, is not known with certainty. Karyotype refers to the number, size, and shape of chromosomes present in the nucleus of a eukaryotic cell. Since Homo habilis is known only from fossil remains, it has not been possible to directly determine its karyotype.

However, based on its evolutionary position as an early member of the Homo genus, scientists infer certain aspects of its genetic makeup and karyotype by studying the genomes and karyotypes of other hominin species, such as Homo sapiens, Neanderthals, and Denisovans, as well as by analyzing similarities and differences in skeletal morphology.

Studies of ancient DNA from fossils, such as those of Neanderthals and Denisovans, have provided insights into the genetic relationships and genomic characteristics of early hominins. By comparing the genomes of these ancient hominins with those of modern humans, scientists can infer some aspects of the genetic makeup and chromosomal structure of ancestral hominins, including Homo habilis.

However, it's important to note that inferring the precise karyotype of Homo habilis based on indirect evidence and comparisons with other species is speculative and subject to revision as new evidence becomes available. Additionally, the study of ancient DNA and the reconstruction of ancient genomes pose significant technical challenges, and our understanding of early hominin genetics continues to evolve as new methods and technologies are developed.

The karyotype of Homo erectus, an extinct species of archaic humans, is not precisely known because it is reconstructed based on indirect evidence and comparisons with modern humans and other hominins. However, scientists have inferred certain aspects of the karyotype of Homo erectus based on fossil evidence and genetic studies.

A karyotype is a visual representation of the chromosomes of an organism, arranged according to size, shape, and banding pattern. In the case of Homo erectus, researchers have suggested that their karyotype would likely resemble that of other hominins, including modern humans.

The typical karyotype of modern humans consists of 46 chromosomes arranged in 23 pairs, with two sex chromosomes (XX for females and XY for males). It is believed that Homo erectus had a similar chromosome count and arrangement to modern humans, as they are considered to be closely related species.

However, without direct fossil evidence of Homo erectus chromosomes, it's challenging to provide a detailed description of their karyotype. Additionally, genetic studies focused on ancient DNA have provided insights into the evolutionary relationships between Homo erectus and other hominins but have not yet yielded information on their specific karyotype.

In summary, while the exact karyotype of Homo erectus remains uncertain, it is inferred to be similar to that of modern humans, with 46 chromosomes arranged in 23 pairs. Further advancements in paleogenomics and ancient DNA analysis may provide additional insights into the genetic makeup of Homo erectus in the future

Homo sapiens.

† Homo antecessor.

The karyotype of Homo antecessor, an extinct hominin species known from fossil remains found in Spain, has not been definitively determined. Karyotyping involves examining the number, size, and shape of chromosomes in a cell, typically through microscopy.

Homo antecessor lived approximately 800,000 to 1.2 million years ago, and no intact chromosomes or DNA samples have been recovered from its fossils. Therefore, scientists have not been able to create a karyotype for this species.

Instead, researchers have inferred aspects of Homo antecessor's biology, including its relationship to other hominin species, based on fossil morphology, isotopic analyses, and genetic studies of related species. However, without direct genetic material from Homo antecessor, creating a karyotype for this species remains speculative.

† Homo erectus.

† Homo ergaster.

† Homo floresiensis.

The karyotype of Homo floresiensis, commonly referred to as the "Flores hobbit," has not been definitively determined due to the limited availability of fossilized remains and the inability to obtain intact chromosomes from ancient specimens.

Homo floresiensis is an extinct species of hominin that lived on the Indonesian island of Flores approximately 50,000 to 100,000 years ago. The species is known primarily from the remains of several individuals found in Liang Bua cave on Flores. These remains include partial skeletons, skull fragments, and isolated bones.

While researchers have conducted extensive analyses on the morphology, genetics, and evolutionary relationships of Homo floresiensis, determining its karyotype— the number, size, and shape of chromosomes—is challenging without intact chromosomes. Additionally, ancient DNA preservation is often poor in fossilized remains, making it difficult to obtain genomic data for karyotyping purposes.

† Homo habilis.

† Homo heidelbergensis.

The karyotype of Homo heidelbergensis, an extinct hominin species, has not been directly observed because karyotype analysis requires intact chromosomes, which cannot be obtained from fossil remains. However, scientists can make educated inferences about the likely karyotype of Homo heidelbergensis based on comparisons with related species and genetic studies.

Homo heidelbergensis is believed to be a direct ancestor of both Homo neanderthalensis (Neanderthals) and Homo sapiens (modern humans). Therefore, scientists often infer aspects of the karyotype of Homo heidelbergensis by studying the karyotypes of these two species and comparing them with those of other closely related hominins, such as Homo erectus.

Based on genetic studies and comparisons with modern humans and Neanderthals, it's likely that Homo heidelbergensis had a karyotype similar to that of modern humans and Neanderthals. This would include a diploid number of 46 chromosomes, consisting of 22 pairs of autosomes and one pair of sex chromosomes (XX in females, XY in males).

However, it's important to note that there may have been some structural differences or variations in the karyotype of Homo heidelbergensis compared to modern humans and Neanderthals, as the hominin lineage underwent evolutionary changes over time. These changes may have included chromosomal rearrangements or other genetic modifications that occurred during the evolution of Homo heidelbergensis and its descendants.

In summary, while the precise karyotype of Homo heidelbergensis cannot be determined directly from fossil evidence, scientists can make informed hypotheses about its likely karyotype based on comparisons with related species and genetic studies.

† Homo longi

Homo longi, also known as the "Dragon Man," is a newly described hominin species based on a fossil skull found in China's Harbin region. However, detailed information about the karyotype of Homo longi is not available because karyotyping involves examining the chromosomes of living organisms, which is not possible for extinct species.

Karyotyping involves arranging and analyzing an individual's chromosomes to determine their number, size, and structure. It requires living cells, typically obtained from blood or tissue samples, which can be cultured and treated to visualize the chromosomes under a microscope. Since Homo longi is an extinct species known only from fossils, it is not possible to perform karyotyping on this species.

However, scientists can make educated guesses about the potential karyotype of Homo longi based on its taxonomic placement within the genus Homo and comparisons with other hominin species, such as Homo sapiens, Neanderthals, and Denisovans. These comparisons can provide insights into the chromosomal characteristics and evolutionary relationships of Homo longi relative to other hominins.

Further research, including genetic analyses and studies of ancient DNA, may provide additional information about the genetic makeup and karyotype of Homo longi. As scientific understanding of this newly described species continues to evolve, researchers may uncover more details about its genetics, morphology, and evolutionary history.

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Karyotype divergence refers to differences in the number, size, and structure of chromosomes among different species. Among primates, both extant (living) and extinct species exhibit notable karyotype divergence. Here, I'll provide an overview of karyotype divergence among some representative primate species, both extant and extinct:

Humans (Homo sapiens):

Humans have a diploid chromosome number of 46 (2n=46), consisting of 22 pairs of autosomes and one pair of sex chromosomes (XX in females and XY in males).

The human karyotype shows distinctive characteristics, including the presence of one large metacentric chromosome pair (chromosome 2) formed by the fusion of two ancestral chromosomes found in other primates.

Chimpanzees (Pan troglodytes):

Chimpanzees have a diploid chromosome number of 48 (2n=48), similar to other great apes.

While chimpanzees share a high degree of genetic similarity with humans, there are differences in chromosomal structure and organization, including inversions and translocations.

Gorillas (Gorilla spp.):

Gorillas have a diploid chromosome number of 48 (2n=48), similar to chimpanzees.

However, there are karyotypic differences between different gorilla species (e.g., western gorillas, eastern gorillas) and subspecies.

Orangutans (Pongo spp.):

Orangutans have a diploid chromosome number of 48 (2n=48), similar to other great apes.

There are significant differences in chromosome morphology and structure between orangutans and other great apes.

Extinct Hominins (e.g., Neanderthals, Denisovans):

Studies of ancient DNA and fossilized remains have provided insights into the karyotypes of extinct hominins.

Neanderthals and Denisovans are known to have had diploid chromosome numbers similar to modern humans, but there were likely structural differences and variations in specific chromosome arrangements.

Other Extinct Primates:

Extinct primates, such as early hominins, australopithecines, and other fossil primates, also exhibited karyotypic diversity.

Studies of fossilized remains and comparative genomics provide clues about the chromosomal characteristics and evolutionary relationships of these extinct primates.

Overall, karyotype divergence among primate species, both extant and extinct, reflects their evolutionary history, genetic relationships, and adaptations to different environments. Studying karyotypic differences can provide valuable insights into primate evolution, speciation, and genomic diversity

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Interbreeding among closely related subspecies of mammals can indeed result in viable and fertile offspring under certain conditions. While there are instances where hybridization between subspecies can lead to reduced fitness or infertility, there are also cases where hybrid offspring exhibit no deleterious effects and may even possess advantageous traits. Here are some key points to consider:

Genetic Compatibility: The success of interbreeding between subspecies often depends on the degree of genetic compatibility between the populations involved. If the subspecies share a recent common ancestor and have retained genetic similarity, they may be more likely to produce viable and fertile hybrid offspring.

Geographic and Ecological Factors: Interbreeding between subspecies is more likely to occur when individuals from different populations come into contact due to changes in habitat, migration patterns, or human-mediated factors. Subspecies that inhabit overlapping ranges or similar environments may have more opportunities for interbreeding.

Hybrid Vigor: In some cases, hybrid offspring may exhibit hybrid vigor or heterosis, where they display enhanced traits compared to their parents. This can occur due to the combination of beneficial alleles from both subspecies, resulting in increased fitness and adaptability.

Reproductive Isolation: While subspecies may differ in certain traits or characteristics, they may not be reproductively isolated from each other. In such cases, there may be little or no barriers to interbreeding, leading to the production of viable and fertile hybrid offspring.

Examples in Nature: There are numerous examples of successful interbreeding between closely related subspecies of mammals. For instance, certain subspecies of wolves, deer, and bears have been known to interbreed where their ranges overlap, resulting in viable and fertile hybrid offspring.

It's important to note that while interbreeding between subspecies can result in viable and fertile offspring, it may also have implications for the genetic integrity and conservation of individual populations. Hybridization can lead to genetic homogenization or the loss of unique adaptations, particularly if one subspecies is rare or endangered. Therefore, conservation efforts often aim to manage hybridization to maintain the distinctiveness and genetic diversity of subspecies where appropriate.

Interbreeding among closely related subspecies of mammals can indeed result in viable and fertile offspring under certain conditions. While there may be some cases where hybridization leads to reduced fertility or viability, it's not uncommon for closely related subspecies to produce healthy offspring with no apparent deleterious effects. Here are some factors that can influence the outcomes of interbreeding among close subspecies:

Genetic Compatibility: If two subspecies are genetically similar and have not diverged significantly in terms of their genetic makeup, they may be more likely to produce viable and fertile hybrids. Genetic compatibility between the parental populations can contribute to the success of hybridization.

Ecological Similarity: Subspecies that inhabit similar environments and ecological niches may be more likely to interbreed successfully. Shared environmental pressures and adaptations can reduce barriers to reproduction between closely related populations.

Geographic Proximity: Physical proximity between subspecies populations can facilitate interbreeding by increasing the likelihood of encounters between individuals from different populations. Subspecies with overlapping ranges are more likely to interbreed than those with geographically isolated populations.

Hybrid Vigor: In some cases, hybrid offspring may exhibit hybrid vigor or heterosis, which refers to the increased fitness and vitality of hybrids compared to their parents. Hybrid vigor can result from the combination of beneficial traits from both parental populations.

Absence of Reproductive Barriers: If there are no significant reproductive barriers between subspecies, such as differences in mating behaviors or reproductive physiology, interbreeding may occur freely, leading to viable and fertile offspring.

Examples of successful interbreeding among closely related subspecies of mammals can be found in various taxa. For instance:

In some cases, different subspecies of wolves (Canis lupus) have been known to interbreed, producing viable and fertile hybrid offspring.

Various subspecies of deer (e.g., white-tailed deer, mule deer) may interbreed where their ranges overlap, producing hybrids known as "zonkeys" or "zonohorses."

While interbreeding among closely related subspecies can result in healthy offspring, it's important to note that hybridization can also have ecological and evolutionary implications, including the potential for genetic introgression and the formation of hybrid zones where gene flow occurs between divergent populations. Additionally, human activities, such as habitat fragmentation and climate change, can influence patterns of hybridization among subspecies.

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The availability of DNA samples from fossil hominins (members of the human evolutionary lineage) varies significantly depending on several factors, including the age and preservation of the fossils, the environments in which they were found, and the techniques used for DNA extraction and analysis. As of my last update in January 2022, here are some notable examples of fossil hominins from which DNA samples have been successfully extracted:

Neanderthals (Homo neanderthalensis):

Neanderthals are one of the best-known extinct hominin species, and DNA has been successfully extracted from multiple fossil specimens found across Europe and Western Asia.

Notable sites include the Neander Valley (Germany), Vindija Cave (Croatia), Denisova Cave (Russia), and various other locations.

The availability of Neanderthal DNA has provided valuable insights into their genetic relationship with modern humans and their contributions to the modern human gene pool through interbreeding.

Denisovans:

Denisovans are another extinct group of hominins known from DNA extracted from a finger bone and a tooth found in Denisova Cave in Siberia, Russia.

While Denisovans are known primarily from genetic data, their fossil remains are limited. However, the available DNA has revealed their genetic distinctiveness from both Neanderthals and modern humans and their contributions to the genetic makeup of present-day populations in Asia and Oceania.

Homo sapiens:

While not fossil hominins in the traditional sense, ancient human remains, such as those found at sites like the Kostenki-Borshchevo sites in Russia and the Paviland Cave in the United Kingdom, have provided valuable DNA samples.

These ancient human DNA samples have contributed to our understanding of the genetic diversity and population history of early Homo sapiens populations.

Other extinct hominins:

Limited DNA data have also been obtained from other extinct hominin species, such as Homo erectus and Homo heidelbergensis. However, the quality and quantity of DNA from these species are generally lower compared to Neanderthals and Denisovans.

It's important to note that DNA preservation in ancient fossils is highly variable and depends on factors such as temperature, humidity, and geological conditions. Additionally, the extraction and analysis of ancient DNA require specialized techniques to minimize contamination and damage to the samples. As a result, DNA samples from fossil hominins are relatively rare and precious, but they have provided invaluable insights into human evolution and prehistory.

several notable fossil discoveries of hominins (members of the human lineage) from various locations around the world. These fossils have provided valuable insights into human evolution, but the availability of DNA from these fossils varies. Here are a few notable examples of fossil hominins and the status of DNA extraction:

Neanderthals (Homo neanderthalensis):

Neanderthals are a well-known extinct human species that lived in Eurasia until approximately 40,000 years ago.

DNA has been successfully extracted from Neanderthal fossils, leading to significant advancements in understanding their genetic relationship to modern humans. The first Neanderthal DNA sequences were obtained in the late 1990s.

Notable Neanderthal DNA samples include those from fossils found in sites such as Vindija Cave (Croatia), Denisova Cave (Siberia), and El Sidrón Cave (Spain).

Denisovans (Denisova hominins):

Denisovans are a group of ancient hominins known primarily from a few fragmentary fossils found in Denisova Cave in Siberia.

DNA analysis of a finger bone and a tooth fragment from Denisova Cave has revealed the existence of a distinct human population that interbred with both Neanderthals and modern humans.

DNA extracted from Denisovan fossils has provided insights into their genetic diversity and their contributions to the genomes of present-day human populations, particularly in Oceania and East Asia.

Homo sapiens (Early Modern Humans):

Fossil remains of early modern humans, Homo sapiens, have been found at numerous sites across Africa, Eurasia, and other regions.

DNA has been successfully extracted from some ancient Homo sapiens fossils, providing insights into the genetic diversity and population history of early human populations.

Notable DNA samples include those from fossils found in sites such as Denisova Cave (Siberia), Atapuerca (Spain), and various locations in Africa.

Other Hominin Fossils:

Other hominin fossils, such as those attributed to Homo erectus, Homo habilis, and Australopithecus species, have been discovered at various sites in Africa and other regions.

While DNA extraction from these fossils has been challenging due to their age and preservation conditions, advances in ancient DNA techniques may eventually enable researchers to obtain genetic information from these specimens.

Overall, DNA extraction from fossil hominins has been most successful in the case of Neanderthals and Denisovans, with limited success in extracting DNA from fossils of other extinct hominin species. However, ongoing advancements in ancient DNA techniques may lead to further discoveries and insights into human evolution.

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The concept of genetic drift refers to the random fluctuations in allele frequencies within a population over time, primarily due to chance events. When considering the genetic drift between extinct and extant mammal species, we're looking at changes in allele frequencies that have occurred over evolutionary time scales. Estimating the exact percentage of DNA from pre-existing species in present-day species is challenging due to the complexity of evolutionary processes, including genetic drift, natural selection, gene flow, and mutation. However, I can provide some general insights:

Genetic Drift and Extinct Species:

Extinct mammal species have left traces of their genetic legacy in the genomes of their extant relatives through processes such as hybridization, introgression, and ancestral genetic variation.

Genetic drift can lead to the fixation or loss of alleles over time, resulting in changes in genetic composition within populations. Small populations or isolated populations are particularly susceptible to genetic drift.

Extinct species may have contributed to the genetic diversity of extant species through hybridization events or by sharing a common ancestral gene pool.

Percentage of DNA from Pre-existing Species:

Estimating the percentage of DNA from pre-existing species in present-day species is challenging due to the dynamic nature of evolutionary processes and the lack of direct genetic data from extinct species.

Some studies have used comparative genomics and phylogenetic analysis to infer patterns of genetic divergence and ancestral relationships between species.

In some cases, genomic studies have identified regions of the genome that show evidence of introgression or shared ancestry between extant and extinct species. These regions may contain a higher percentage of DNA inherited from pre-existing species.

However, it's important to note that genetic contributions from extinct species may vary widely among extant species, depending on factors such as their evolutionary history, geographic distribution, and degree of genetic isolation.

Overall, while genetic drift and contributions from extinct species have played important roles in shaping the genomes of extant mammal species, quantifying the exact percentage of DNA from pre-existing species in present-day genomes remains a complex and ongoing area of research in evolutionary biology and genomics.

Genetic drift refers to the random fluctuations in allele frequencies within a population over time due to chance events. When considering the genetic drift of mammal species between extinct and extant species, it's important to recognize that genetic drift operates on a population level and can have varying effects over long periods of time. Additionally, estimating the percentage of DNA from pre-existing species in modern species is complex and depends on factors such as evolutionary relationships, population history, and genetic admixture.

Here's a general overview of how genetic drift might influence the genetic composition of extant mammal species compared to their extinct ancestors, as well as considerations for estimating the percentage of DNA from pre-existing species:

Genetic Drift in Extinct and Extant Mammal Species:

Over time, genetic drift can lead to changes in allele frequencies within populations, potentially resulting in the fixation of certain alleles or the loss of genetic variation.

Extinct mammal species experienced genetic drift during their evolutionary history, influenced by factors such as population size, geographic isolation, and environmental changes.

Extant mammal species also undergo genetic drift, and the effects of genetic drift can accumulate over generations, leading to genetic divergence between populations and species.

Percentage of DNA from Pre-existing Species:

Estimating the percentage of DNA from pre-existing species in modern species involves analyzing genetic data from extant organisms and inferring their evolutionary relationships with extinct species.

Techniques such as phylogenetic analysis, comparative genomics, and ancient DNA analysis can provide insights into the genetic relatedness between extinct and extant species.

The percentage of DNA from pre-existing species in modern species can vary depending on the degree of shared ancestry, genetic introgression, and admixture events.

For example, in the case of hybridization between extinct and extant species (e.g., Neanderthals and modern humans), genetic analyses have revealed varying levels of introgression, with modern human populations outside of Africa carrying approximately 1-2% Neanderthal DNA.

Overall, genetic drift plays a role in shaping the genetic diversity and composition of mammal species over evolutionary time scales. Estimating the percentage of DNA from pre-existing species in modern species requires sophisticated genetic analyses and considerations of evolutionary history, population dynamics, and genetic processes such as introgression and admixture.

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Comparing the genomes of Homo sapiens (modern humans) and Homo neanderthalensis (Neanderthals) is a complex task that involves examining various aspects, including DNA content, number of genes, alleles, and codons. Here's a comparison based on available scientific knowledge as of my last update in January 2022:

Genome Size:

The genome size of both Homo sapiens and Homo neanderthalensis is estimated to be approximately 3 billion base pairs (3 gigabases or 3 Gb) of DNA.

Number of Genes:

Both Homo sapiens and Homo neanderthalensis have a similar number of protein-coding genes, estimated to be around 19,000 to 20,000 genes. However, the exact number of genes can vary depending on the criteria used for gene annotation and analysis.

Allele Variation:

Studies comparing the genomes of modern humans and Neanderthals have revealed evidence of genetic variation and allele sharing between the two species. Modern humans of non-African descent carry approximately 1-2% Neanderthal DNA in their genomes, indicating past interbreeding between the two groups. This interbreeding has led to the presence of Neanderthal alleles in the modern human gene pool.

Codon Usage:

Codons are sequences of three nucleotides that code for specific amino acids in protein synthesis. The codon usage in the genomes of Homo sapiens and Homo neanderthalensis is likely to be similar, as both species share a common genetic code. However, subtle differences in codon usage and frequency may exist between the two species due to genetic drift, natural selection, and other evolutionary factors.

Decoded Genomic Regions:

Decoding the entire genomic sequence of Homo sapiens and Homo neanderthalensis has provided insights into their genetic similarities and differences. Comparative genomic studies have identified regions of the genome that show evidence of positive selection, introgression, and genetic adaptation in both species.

Overall, while Homo sapiens and Homo neanderthalensis share a significant portion of their genetic heritage, there are also distinct genetic differences between the two species. Comparative genomics studies have provided valuable insights into the evolutionary history and genetic relationships between modern humans and Neanderthals, shedding light on the genetic factors that have shaped human diversity and adaptation.

Comparing the genomes of Homo sapiens (modern humans) and Homo neanderthalensis (Neanderthals) involves examining various aspects such as DNA size, number of genes, alleles, and codons. While the genomes of both species are similar in many respects, there are also notable differences reflecting their evolutionary history and divergence. Here's a comparison based on available scientific knowledge:

DNA Size (Kilobases, kb):

The size of the nuclear genome for both Homo sapiens and Homo neanderthalensis is approximately 3.2 billion base pairs (bp). This corresponds to approximately 3,200 megabases (Mb) or 3.2 gigabases (Gb).

Both species have a similar genome size, indicating a comparable amount of genetic information encoded in their DNA.

Number of Genes:

Homo sapiens is estimated to have around 19,000-20,000 protein-coding genes in its genome.

While the exact number of genes in the Neanderthal genome is not precisely known, estimates suggest that Neanderthals likely had a similar number of protein-coding genes as modern humans.

Alleles:

Alleles are alternative forms of genes that arise by mutation and are found at the same location on a chromosome. Both Homo sapiens and Homo neanderthalensis would have had numerous alleles across their genomes.

While specific information about the number of alleles in each species is not readily available, it's expected that both species would have had allelic diversity within their populations.

Codons:

Codons are sequences of three nucleotides in DNA or RNA that correspond to specific amino acids during protein synthesis. Both Homo sapiens and Homo neanderthalensis would have utilized the same genetic code, with each codon encoding for a particular amino acid.

The exact number of codons in the genomes of both species would be determined by the size of their protein-coding regions and the number of genes.

Decoded Regions:

Both Homo sapiens and Homo neanderthalensis have had various regions of their genomes decoded through genome sequencing efforts. These decoded regions include protein-coding genes, non-coding regions, regulatory sequences, and repetitive elements.

Comparative genomics studies have identified regions of similarity and divergence between the genomes of modern humans and Neanderthals, shedding light on their shared ancestry and unique evolutionary trajectories.

Overall, while Homo sapiens and Homo neanderthalensis share many similarities in their genomes, there are also notable differences reflecting their distinct evolutionary histories and adaptations to different environments. Comparative genomics studies continue to provide insights into the genetic relationships between modern humans and Neanderthals, illuminating the complexities of human evolution.

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After a brief review of the most recent findings in the study of human evolution, an extensive comparison of the complete genomes of our nearest relative, the chimpanzee (Pan troglodytes), of extant Homo sapiens, archaic Homo neanderthalensis and the Denisova specimen were made. The focus was on non-synonymous mutations, which consequently had an impact on protein levels and these changes were classified according to degree of effect. A total of 10,447 non-synonymous substitutions were found in which the derived allele is fixed or nearly fixed in humans as compared to chimpanzee. Their most frequent location was on chromosome 21. Their presence was then searched in the two archaic genomes. Mutations in 381 genes would imply radical amino acid changes, with a fraction of these related to olfaction and other important physiological processes. Eight new alleles were identified in the Neanderthal and/or Denisova genetic pools. Four others, possibly affecting cognition, occured both in the sapiens and two other archaic genomes. The selective sweep that gave rise to Homo sapiens could, therefore, have initiated before the modern/archaic human divergence

Paixão-Côrtes VR, Viscardi LH, Salzano FM, Hünemeier T, Bortolini MC. Homo sapiens, Homo neanderthalensis and the Denisova specimen: New insights on their evolutionary histories using whole-genome comparisons. Genet Mol Biol. 2012 Dec;35(4 (suppl)):904-11. doi: 10.1590/s1415-47572012000600003. Epub 2012 Dec 18. PMID: 23413113; PMCID: PMC3571422.

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https://www.unige.ch/medias/en/2023/la-rencontre-entre-neandertal-et-sapiens-racontee-par-leurs-genomes

The encounter between Neanderthals and Sapiens as told by their genomes

By analyzing genomes up to 40,000 years old, a UNIGE team has traced the history of migrations between Sapiens and Neanderthals.

The UNIGE team analysed the distribution of the portion of DNA inherited from Neanderthals in the genomes of humans (Homo sapiens) over the last 40,000 years. © Claudio Quilodrán

About 40,000 years ago, Neanderthals, who had lived for hundreds of thousands of years in the western part of the Eurasian continent, gave way to Homo sapiens, who had arrived from Africa. This replacement was not sudden, and the two species coexisted for a few millennia, resulting in the integration of Neanderthal DNA into the genome of Sapiens. Researchers at the University of Geneva (UNIGE) have analyzed the distribution of the portion of DNA inherited from Neanderthals in the genomes of humans (Homo sapiens) over the last 40,000 years. These statistical analyses revealed subtle variations in time and geographical space. This work, published in the journal Science Advances, helps us to understand the common history of these two species.

Thanks to genome sequencing and comparative analysis, it is established that Neanderthals and Sapiens interbred and that these encounters were sometimes fruitful, leading to the presence of about 2% of DNA of Neanderthal origin in present-day Eurasians. However, this percentage varies slightly between regions of Eurasia, since DNA from Neanderthals is somewhat more abundant in the genomes of Asian populations than in those of European populations.

One hypothesis to explain this difference is that natural selection would not have had the same effect on genes of Neanderthal origin in Asian and European populations. Mathias Currat’s team, senior lecturer in the Department of Genetics and Evolution at the UNIGE Faculty of Science, is working on another hypothesis. His previous work, based on computer simulations, suggests that such differences could be explained by migratory flows: when a migrant population hybridizes with a local population, in their area of cohabitation, the proportion of DNA of the local population tends to increase with distance from the point of departure of the migrant population.

Europe: a territory shared by both species

In the case of Sapiens and Neanderthals, the hypothesis is that the further one moves away from Africa, Homo sapiens’ point of origin, the greater the proportion of DNA from Neanderthal, a population mainly located in Europe. To test this hypothesis, the authors used a database made available by Harvard Medical School that includes more than 4,000 genomes from individuals who have lived in Eurasia over the past 40 millennia.

‘‘Our study is mainly focused on European populations since we are obviously dependent on the discovery of bones and the state of conservation of DNA. It turns out that archaeological excavations have been much more numerous in Europe, which greatly facilitates the study of the genomes of European populations,’’ explains Claudio Quilodrán, senior research and teaching assistant in the Department of Genetics and Evolution at the UNIGE Faculty of Science, and co-first author of the study.

Statistical analyses revealed that, in the period following the dispersal of Homo sapiens from Africa, the genomes of Paleolithic hunter-gatherers who lived in Europe contained a slightly higher proportion of DNA of Neanderthal origin than the genomes of those who lived in Asia. This result is contrary to the current situation but in agreement with paleontological data, since the presence of Neanderthals was mainly reported in western Eurasia (no Neanderthal bones have been discovered further east than the Altai region of Siberia).

The arrival of Anatolian farmers modifies genomes

Subsequently, during the transition to the Neolithic, i.e. the transition from the hunter-gatherer lifestyle to the farmer lifestyle, 10,000 to 5,000 years ago, the study shows a decline in the proportion of DNA of Neanderthal origin in the genomes of European populations, resulting in a slightly lower percentage than that of Asian populations (as currently observed). This decrease coincided with the arrival in Europe of the first farmers from Anatolia (Turkey’s western peninsula) and the Aegean area, who themselves carried a lower proportion of DNA of Neanderthal origin than the inhabitants of Europe at the same time. By mixing with the populations of Europe, the genomes of farmers from Anatolia ‘‘diluted’’ Neanderthal DNA a little more.

This study shows that the analysis of ancient genomes, coupled with archaeological data, makes it possible to trace different stages in the history of hybridized species. ‘‘In addition, we are beginning to have enough data to describe more and more precisely the percentage of DNA of Neanderthal origin in the genome of Sapiens at certain periods of prehistory. Our work can therefore serve as a reference for future studies to more easily detect genetic profiles that deviate from the average and might therefore disclose an advantageous or disadvantageous effect,’’ concludes Mathias Currat, last author of the study.

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a general overview of some morphological and genetic characteristics that have been observed among the populations you mentioned. Please note that these are broad generalizations and there is significant diversity within each population group. Additionally, factors such as migration, intermixing, and environmental influences can complicate any attempt to categorize populations into distinct groups.

Pigmeo (Pygmy) People:

DNA: Pygmy populations, such as the African Pygmies, exhibit genetic adaptations to their rainforest environment, including certain immune system genes.

Skull Shape: Typically characterized by a more gracile cranial morphology.

Height: Generally shorter stature compared to other populations, with an average height around 4 to 5 feet.

Proportion of Extremities: Proportions may vary but tend to be adapted to their environment, which often includes dense forests.

Skin Pigmentation: Varies, but tends to be darker due to living in equatorial regions.

Eyes Color: Varies, though darker eye colors such as brown are common.

Hair Type: Often tightly coiled or curly hair.

Blood Type and rH Factor Frequencies: Can vary but may include ABO blood types common in other African populations.

New Guinea People:

DNA: Diverse genetic makeup due to the significant linguistic and cultural diversity in the region.

Skull Shape: Can vary among different ethnic groups, but some may have more robust cranial features.

Height: Generally shorter stature compared to many Western populations.

Proportion of Extremities: Adaptations may vary depending on the specific environmental challenges of different regions within New Guinea.

Skin Pigmentation: Varies among different ethnic groups, with some having darker skin tones due to sun exposure.

Eyes Color: Varies, but darker eye colors are common.

Hair Type: Can range from straight to curly depending on the ethnic group.

Blood Type and rH Factor Frequencies: Varies among different ethnic groups.

Holland (Dutch) People:

DNA: Typical of European populations, with variations based on historical migrations and interactions.

Skull Shape: Generally characterized by a mesocephalic or dolichocephalic cranial morphology.

Height: Taller on average compared to global populations.

Proportion of Extremities: Typically within the range of other European populations.

Skin Pigmentation: Generally fair to light skin due to less sunlight exposure.

Eyes Color: Blue and green eyes are more common, though brown is also present.

Hair Type: Straight to wavy hair, with various colors ranging from blonde to brown.

Blood Type and rH Factor Frequencies: Commonly includes ABO blood types and rhesus positive (Rh+) factor.

Eskimo (Inuit) People:

DNA: Unique genetic adaptations to cold environments, including certain metabolic genes.

Skull Shape: Typically characterized by a broader cranial morphology, an adaptation to the cold climate.

Height: Generally similar to other indigenous populations, with some variation among different Inuit groups.

Proportion of Extremities: May have shorter limbs relative to trunk length, an adaptation to retain heat.

Skin Pigmentation: Typically brown to light brown, with adaptations to UV radiation.

Eyes Color: Dark brown is common, though lighter colors may also occur.

Hair Type: Straight to wavy hair, often black.

Blood Type and rH Factor Frequencies: Frequencies can vary, but typically include ABO blood types and Rh+ factor.

Semitic People:

DNA: Broadly categorized within the larger West Eurasian genetic cluster, with various subgroups.

Skull Shape: Can vary but often characterized by a mesocephalic cranial morphology.

Height: Average height may vary among different Semitic populations.

Proportion of Extremities: Generally within the range of other West Eurasian populations.

Skin Pigmentation: Varies among different Semitic populations, ranging from light to olive complexion.

Eyes Color: Brown is common, though lighter eye colors may also occur.

Hair Type: Can vary from straight to curly, with colors ranging from dark brown to black.

Blood Type and rH Factor Frequencies: Frequencies can vary among different Semitic populations.

Tibetan People:

DNA: Unique genetic adaptations to high-altitude environments, including genes related to oxygen metabolism.

Skull Shape: Generally characterized by adaptations to high-altitude living, such as a larger lung capacity.

Height: Similar to other East Asian populations, though some variation may exist.

Proportion of Extremities: Adaptations to cold climates may include shorter limbs relative to trunk length.

Skin Pigmentation: Typically fair to light brown.

Eyes Color: Dark brown is common, though lighter eye colors may also occur.

Hair Type: Straight to wavy hair, with dark colors being common.

Blood Type and rH Factor Frequencies: Frequencies can vary, but may include ABO blood types and Rh+ factor.

Guarani People:

DNA: Indigenous South American populations with genetic diversity influenced by long-term isolation and subsequent interactions with other groups.

Skull Shape: Varies among different Guarani subgroups.

Height: Can vary but generally shorter stature compared to Western populations.

Proportion of Extremities: Adaptations may vary based on environmental factors.

Skin Pigmentation: Typically ranges from light brown to darker tones.

Eyes Color: Brown is common, though lighter eye colors may also occur.

Hair Type: Can range from straight to wavy, with dark colors being common.

Blood Type and rH Factor Frequencies: Frequencies can vary, but may include ABO blood types and Rh+ factor.

Patagon People:

DNA: Indigenous peoples of the Patagonia region with genetic diversity influenced by historical migrations and interactions.

Skull Shape: Varies among different Patagonian groups.

Height: Can vary but generally shorter stature compared to Western populations.

Proportion of Extremities: Adaptations may vary based on environmental factors.

Skin Pigmentation: Typically ranges from light brown to darker tones.

Eyes Color: Brown is common, though lighter eye colors may also occur.

Hair Type: Can range from straight to wavy, with dark colors being common.

**Blood Type and r

Morphological and genetic phenotype differences among: Pigmeo, New Guinea, Holland, Eskimo, Semitic, Tibetan, Guarani, Patagon and Georgian people DNA, skull shape, height, proportion of extremities, skin pigmentation, eyes color, hair type, blood type, rH factor frequencies.

Pigmeo,

New Guinea,

Holland,

Eskimo,

Semitic,

Tibetan,

Guarani,

Patagon

Georgian

---------

Homo (from Latin homō 'human') is a monotypic genus that emerged from the genus Australopithecus and encompasses the extant species Homo sapiens (modern humans) and several extinct species classified as either ancestral to or closely related to modern humans, including Homo erectus and Homo neanderthalensis. The oldest member of the genus is Homo habilis, with records of just over 2 million years ago.[a] Homo, together with the genus Paranthropus, is probably sister to Australopithecus africanus, which itself had split from the lineage of Pan, the chimpanzees.[b][4][5]

Homo erectus appeared about 2 million years ago and spread throughout Africa (where it is called H. ergaster) and Eurasia in several migrations. An adaptive and successful species, H. erectus persisted for more than a million years and gradually diverged into new species by around 500,000 years ago.[c][6] Based on genetic studies, a human ancestor population bottleneck (from a possible 100,000 to 1000 individuals) occurred "around 930,000 and 813,000 years ago ... lasted for about 117,000 years and brought human ancestors close to extinction."[7][8]

Anatomically modern humans (Homo sapiens) emerged close to 300,000 to 200,000 years ago,[9] in Africa, and H. neanderthalensis emerged around the same time in Europe and Western Asia. H. sapiens dispersed from Africa in several waves, from possibly as early as 250,000 years ago, and certainly by 130,000 years ago, with the so-called Southern Dispersal beginning about 70–50,000 years ago[10][11][12] leading to the lasting colonisation of Eurasia and Oceania by 50,000 years ago. H. sapiens met and interbred with archaic humans in Africa and in Eurasia.[13][14] Separate archaic (non-sapiens) human species are thought to have survived until around 40,000 years ago (Neanderthal extinction).

Names and taxonomy

Main articles: Human taxonomy, Names for the human species, and Homininae

Evolutionary tree chart emphasizing the subfamily Homininae and the tribe Hominini. After diverging from the line to Ponginae, the early Homininae split into the tribes Hominini and Gorillini. The early Hominini split further, separating the line to Homo from the lineage of Pan. Currently, tribe Hominini designates the subtribes Hominina, containing genus Homo; Panina, genus Pan; and Australopithecina, with several extinct genera—the subtribes are not labelled on this chart.

The Latin noun homō (genitive hominis) means "human being" or "man" in the generic sense of "human being, mankind".[d] The binomial name Homo sapiens was coined by Carl Linnaeus (1758).[e][17] Names for other species of the genus were introduced from the second half of the 19th century (H. neanderthalensis 1864, H. erectus 1892).

The genus Homo has not been strictly defined, even today.[18][19][20] Since the early human fossil record began to slowly emerge from the earth, the boundaries and definitions of the genus have been poorly defined and constantly in flux. Because there was no reason to think it would ever have any additional members, Carl Linnaeus did not even bother to define Homo when he first created it for humans in the 18th century. The discovery of Neanderthal brought the first addition.

The genus Homo was given its taxonomic name to suggest that its member species can be classified as human. And, over the decades of the 20th century, fossil finds of pre-human and early human species from late Miocene and early Pliocene times produced a rich mix for debating classifications. There is continuing debate on delineating Homo from Australopithecus—or, indeed, delineating Homo from Pan. Even so, classifying the fossils of Homo coincides with evidence of: (1) competent human bipedalism in Homo habilis inherited from the earlier Australopithecus of more than four million years ago, as demonstrated by the Laetoli footprints; and (2) human tool culture having begun by 2.5 million years ago to 3 million years ago.[21]

From the late-19th to mid-20th centuries, a number of new taxonomic names, including new generic names, were proposed for early human fossils; most have since been merged with Homo in recognition that Homo erectus was a single species with a large geographic spread of early migrations. Many such names are now regarded as "synonyms" with Homo, including Pithecanthropus,[22] Protanthropus,[23] Sinanthropus,[24] Cyphanthropus,[25] Africanthropus,[26] Telanthropus,[27] Atlanthropus,[28] and Tchadanthropus.[29][30]

Classifying the genus Homo into species and subspecies is subject to incomplete information and remains poorly done. This has led to using common names ("Neanderthal" and "Denisovan"), even in scientific papers, to avoid trinomial names or the ambiguity of classifying groups as incertae sedis (uncertain placement)—for example, H. neanderthalensis vs. H. sapiens neanderthalensis, or H. georgicus vs. H. erectus georgicus.[31] Some recently extinct species in the genus have been discovered only lately and do not as yet have consensus binomial names (see Denisova hominin).[32] Since the beginning of the Holocene, it is likely that Homo sapiens (anatomically modern humans) has been the only extant species of Homo.

John Edward Gray (1825) was an early advocate of classifying taxa by designating tribes and families.[33] Wood and Richmond (2000) proposed that Hominini ("hominins") be designated as a tribe that comprised all species of early humans and pre-humans ancestral to humans back to after the chimpanzee–human last common ancestor, and that Hominina be designated a subtribe of Hominini to include only the genus Homo — that is, not including the earlier upright walking hominins of the Pliocene such as Australopithecus, Orrorin tugenensis, Ardipithecus, or Sahelanthropus.[34] Designations alternative to Hominina existed, or were offered: Australopithecinae (Gregory & Hellman 1939) and Preanthropinae (Cela-Conde & Altaba 2002);[35][36][37] and later, Cela-Conde and Ayala (2003) proposed that the four genera Australopithecus, Ardipithecus, Praeanthropus, and Sahelanthropus be grouped with Homo within Hominini (sans Pan).[36]

Evolution

Main article: Human evolution

Further information: Timeline of human evolution, Hominini, and Chimpanzee–human last common ancestor

Australopithecus and the appearance of Homo

Further information: Australopithecus

Several species, including Australopithecus garhi, Australopithecus sediba, Australopithecus africanus, and Australopithecus afarensis, have been proposed as the ancestor or sister of the Homo lineage.[38][39] These species have morphological features that align them with Homo, but there is no consensus as to which gave rise to Homo.

Especially since the 2010s, the delineation of Homo in Australopithecus has become more contentious. Traditionally, the advent of Homo has been taken to coincide with the first use of stone tools (the Oldowan industry), and thus by definition with the beginning of the Lower Palaeolithic. But in 2010, evidence was presented that seems to attribute the use of stone tools to Australopithecus afarensis around 3.3 million years ago, close to a million years before the first appearance of Homo.[40] LD 350-1, a fossil mandible fragment dated to 2.8 Mya, discovered in 2013 in Afar, Ethiopia, was described as combining "primitive traits seen in early Australopithecus with derived morphology observed in later Homo.[41] Some authors would push the development of Homo close to or even past 3 Mya.[f] This finds support in a recent phylogenetic study in hominins that by using morphological, molecular and radiometric information, dates the emergence of Homo at 3.3 Ma (4.30 – 2.56 Ma). [42] Others have voiced doubt as to whether Homo habilis should be included in Homo, proposing an origin of Homo with Homo erectus at roughly 1.9 Mya instead.[43]

The most salient physiological development between the earlier australopithecine species and Homo is the increase in endocranial volume (ECV), from about 460 cm3 (28 cu in) in A. garhi to 660 cm3 (40 cu in) in H. habilis and further to 760 cm3 (46 cu in) in H. erectus, 1,250 cm3 (76 cu in) in H. heidelbergensis and up to 1,760 cm3 (107 cu in) in H. neanderthalensis. However, a steady rise in cranial capacity is observed already in Autralopithecina and does not terminate after the emergence of Homo, so that it does not serve as an objective criterion to define the emergence of the genus.[44]

Homo habilis

Homo habilis emerged about 2.1 Mya. Already before 2010, there were suggestions that H. habilis should not be placed in the genus Homo but rather in Australopithecus.[45][46] The main reason to include H. habilis in Homo, its undisputed tool use, has become obsolete with the discovery of Australopithecus tool use at least a million years before H. habilis.[40] Furthermore, H. habilis was long thought to be the ancestor of the more gracile Homo ergaster (Homo erectus). In 2007, it was discovered that H. habilis and H. erectus coexisted for a considerable time, suggesting that H. erectus is not immediately derived from H. habilis but instead from a common ancestor.[47] With the publication of Dmanisi skull 5 in 2013, it has become less certain that Asian H. erectus is a descendant of African H. ergaster which was in turn derived from H. habilis. Instead, H. ergaster and H. erectus appear to be variants of the same species, which may have originated in either Africa or Asia[48] and widely dispersed throughout Eurasia (including Europe, Indonesia, China) by 0.5 Mya.[49]

Homo erectus

Main article: Homo erectus

Homo erectus has often been assumed to have developed anagenetically from H. habilis from about 2 million years ago. This scenario was strengthened with the discovery of Homo erectus georgicus, early specimens of H. erectus found in the Caucasus, which seemed to exhibit transitional traits with H. habilis. As the earliest evidence for H. erectus was found outside of Africa, it was considered plausible that H. erectus developed in Eurasia and then migrated back to Africa. Based on fossils from the Koobi Fora Formation, east of Lake Turkana in Kenya, Spoor et al. (2007) argued that H. habilis may have survived beyond the emergence of H. erectus, so that the evolution of H. erectus would not have been anagenetically, and H. erectus would have existed alongside H. habilis for about half a million years (1.9 to 1.4 million years ago), during the early Calabrian.[47] On 31 August 2023, researchers reported, based on genetic studies, that a human ancestor population bottleneck (from a possible 100,000 to 1000 individuals) occurred "around 930,000 and 813,000 years ago ... lasted for about 117,000 years and brought human ancestors close to extinction."[7][8]

A separate South African species Homo gautengensis has been postulated as contemporary with H. erectus in 2010.[50]

Phylogeny

Hominin timeline

This box: viewtalkedit

−10 —–−9 —–−8 —–−7 —–−6 —–−5 —–−4 —–−3 —–−2 —–−1 —–0 —

Miocene

Pliocene

Pleistocene

Hominini

Nakalipithecus

Samburupithecus

Ouranopithecus

(Ou. turkae)

(Ou. macedoniensis)

Chororapithecus

Oreopithecus

Sivapithecus

Sahelanthropus

Graecopithecus

Orrorin

(O. praegens)

(O. tugenensis)

Ardipithecus

(Ar. kadabba)

(Ar. ramidus)

Australopithecus

(Au. africanus)

(Au. afarensis)

(Au. anamensis)

H. habilis

(H. rudolfensis)

(Au. garhi)

H. erectus

(H. antecessor)

(H. ergaster)

(Au. sediba)

H. heidelbergensis

Homo sapiens

Neanderthals

Denisovans

←

Earlier apes

←

Gorilla split

←

Chimpanzee split

←

Earliest bipedal

←

Earliest sign of Ardipithecus

←

Earliest sign of Australopithecus

←

Earliest stone tools

←

Earliest sign of

Homo

←

Dispersal beyond Africa

←

Earliest fire / cooking

←

Earliest rock art

←

Earliest clothes

←

Modern humans

(million years ago)

A taxonomy of Homo within the great apes is assessed as follows, with Paranthropus and Homo emerging within Australopithecus (shown here cladistically granting Paranthropus, Kenyanthropus, and Homo).[a][b][6][51][4][5][52][53][54][55][56][57][58][excessive citations] The exact phylogeny within Australopithecus is still highly controversial. Approximate radiation dates of daughter clades are shown in millions of years ago (Mya).[59][55] Graecopithecus, Sahelanthropus, Orrorin, possibly sisters to Australopithecus, are not shown here. The naming of groupings is sometimes muddled as often certain groupings are presumed before any cladistic analysis is performed.[53]

Hominoidea

Hylobatidae (gibbons)

Hominidae

Ponginae (orangutans)

Homininae

Gorillini (gorillas)

Hominini

Panina (chimpanzees)

Australopithecines (incl. Australopithecus, Kenyanthropus, Paranthropus, Homo)

(7.5)

(8.8)

(15.7)

(20.4 Mya)

Australopithecines

Ardipithecus ramidus (†)

Australopithecus s.l.

Australopithecus anamensis s.s. (†3.8)

Australopithecus afarensis (†)

Australopithecus garhi (†)

Australopithecus deyiremeda (†3.4)

Kenyanthropus platyops (†3.3)

Australopithecus africanus (†2.1)

Paranthropus (†1.2)

Homo

Homo habilis (†1.5)

Homo rudolfensis (†1.9)

H. erectus s.l.

Homo ergaster (†1.4)

African Homo erectus s.s. (†)

Asian Homo erectus s.s. (†0.1)

(1.5)

Homo antecessor (†0.8)

Homo heidelbergensis

Neandersovans

H. neanderthalensis (†0.05)

Denisova people (†0.05)

(0.3)

Homo sapiens

(0.5)

(2.4)

Australopithecus sediba (†2.0)

Homo floresiensis (†0.05)

(3.3)

(5.5)

(7.3 Mya)

Several of the Homo lineages appear to have surviving progeny through introgression into other lines. Genetic evidence indicates an archaic lineage separating from the other human lineages 1.5 million years ago, perhaps H. erectus, may have interbred into the Denisovans about 55,000 years ago.[60][52][61] Fossil evidence shows H. erectus s.s. survived at least until 117,000 yrs ago, and the even more basal H. floresiensis survived until 50,000 years ago. A 1.5-million-year H. erectus-like lineage appears to have made its way into modern humans through the Denisovans and specifically into the Papuans and aboriginal Australians.[52] The genomes of non-sub-Saharan African humans show what appear to be numerous independent introgression events involving Neanderthal and in some cases also Denisovans around 45,000 years ago.[62][61] The genetic structure of some sub-Saharan African groups seems to be indicative of introgression from a west Eurasian population some 3,000 years ago.[56][63]

Some evidence suggests that Australopithecus sediba could be moved to the genus Homo, or placed in its own genus, due to its position with respect to e.g. H. habilis and H. floresiensis.[54][64]

Dispersal

See also: Early expansions of hominins out of Africa, Interbreeding between archaic and modern humans, and Early human migrations

By about 1.8 million years ago, H. erectus is present in both East Africa (H. ergaster) and in Western Asia (H. georgicus). The ancestors of Indonesian H. floresiensis may have left Africa even earlier.[g][54]

Successive dispersals of Homo erectus (yellow), H. neanderthalensis (ochre) and H. sapiens (red)

Homo erectus and related or derived archaic human species over the next 1.5 million years spread throughout Africa and Eurasia[65][66] (see: Recent African origin of modern humans). Europe is reached by about 0.5 Mya by Homo heidelbergensis.

Homo neanderthalensis and H. sapiens develop after about 300 kya. Homo naledi is present in Southern Africa by 300 kya.

H. sapiens soon after its first emergence spread throughout Africa, and to Western Asia in several waves, possibly as early as 250 kya, and certainly by 130 kya. In July 2019, anthropologists reported the discovery of 210,000 year old remains of a H. sapiens and 170,000 year old remains of a H. neanderthalensis in Apidima Cave, Peloponnese, Greece, more than 150,000 years older than previous H. sapiens finds in Europe.[67][68][69]

Most notable is the Southern Dispersal of H. sapiens around 60 kya, which led to the lasting peopling of Oceania and Eurasia by anatomically modern humans.[13] H. sapiens interbred with archaic humans both in Africa and in Eurasia, in Eurasia notably with Neanderthals and Denisovans.[70][71]

Among extant populations of H. sapiens, the deepest temporal division is found in the San people of Southern Africa, estimated at close to 130,000 years,[72] or possibly more than 300,000 years ago.[73] Temporal division among non-Africans is of the order of 60,000 years in the case of Australo-Melanesians. Division of Europeans and East Asians is of the order of 50,000 years, with repeated and significant admixture events throughout Eurasia during the Holocene.

Archaic human species may have survived until the beginning of the Holocene, although they were mostly extinct or absorbed by the expanding H. sapiens populations by 40 kya (Neanderthal extinction).

List of lineages

See also: List of human evolution fossils

The species status of H. rudolfensis, H. ergaster, H. georgicus, H. antecessor, H. cepranensis, H. rhodesiensis, H. neanderthalensis, Denisova hominin, and H. floresiensis remain under debate. H. heidelbergensis and H. neanderthalensis are closely related to each other and have been considered to be subspecies of H. sapiens.

There has historically been a trend to postulate new human species based on as little as an individual fossil. A "minimalist" approach to human taxonomy recognizes at most three species, H. habilis (2.1–1.5 Mya, membership in Homo questionable), H. erectus (1.8–0.1 Mya, including the majority of the age of the genus, and the majority of archaic varieties as subspecies,[74][75][76] including H. heidelbergensis as a late or transitional variety[77][78][79]) and Homo sapiens (300 kya to present, including H. neanderthalensis and other varieties as subspecies). Consistent definitions and methodology of species delineation are not generally agreed upon in anthropology or paleontology. Indeed, speciating populations of mammals can typically interbreed for several million years after they begin to genetically diverge,[80][81] so all contemporary "species" in the genus Homo would potentially have been able to interbreed at the time, and introgression from beyond the genus Homo can not a priori be ruled out.[82] It has been suggested that H. naledi may have been a hybrid with a late surviving Australipith (taken to mean beyond Homo, ed.),[51] despite the fact that these lineages generally are regarded as long extinct. As discussed above, many introgressions have occurred between lineages, with evidence of introgression after separation of 1.5 million years.

Comparative table of Homo lineages

Lineages Temporal range

(kya) Habitat Adult height Adult mass Cranial capacity

(cm3) Fossil record Discovery/

publication

of name

H. habilis

membership in Homo uncertain 2,100–1,500[h][i] Tanzania 110–140 cm (3 ft 7 in – 4 ft 7 in) 33–55 kg (73–121 lb) 510–660 Many 1960

1964

H. rudolfensis

membership in Homo uncertain 1,900 Kenya 700 2 sites 1972

1986

H. gautengensis

also classified as H. habilis 1,900–600 South Africa 100 cm (3 ft 3 in) 3 individuals[85][j] 2010

2010

H. erectus 1,900–140[86][k][87][l] Africa, Eurasia 180 cm (5 ft 11 in) 60 kg (130 lb) 850 (early) – 1,100 (late) Many[m][n] 1891

1892

H. ergaster

African H. erectus 1,800–1,300[89] East and Southern Africa 700–850 Many 1949

1975

H. antecessor 1,200–800 Western Europe 175 cm (5 ft 9 in) 90 kg (200 lb) 1,000 2 sites 1994

1997

H. heidelbergensis

early H. neanderthalensis 600–300[o] Europe, Africa 180 cm (5 ft 11 in) 90 kg (200 lb) 1,100–1,400 Many 1907

1908

H. cepranensis

a single fossil, possibly H. heidelbergensis c. 450[90] Italy 1,000 1 skull cap 1994

2003

H. naledi 335—236[91] South Africa 150 cm (4 ft 11 in) 45 kg (99 lb) 450 15 individuals 2013

2015

H. longi 309–138[92] Northeast China 1,420[93] 1 individual 1933

2021

H. rhodesiensis

early H. sapiens c. 300 Zambia 1,300 Single or very few 1921

1921

H. sapiens

(anatomically modern humans) c. 300–present[p] Worldwide 150–190 cm (4 ft 11 in – 6 ft 3 in) 50–100 kg (110–220 lb) 950–1,800 (extant) ——

1758

Denisova hominin c. 285 - c. 51 Siberia 2 sites 2000

2010[q]

H. neanderthalensis

240–40[96][r] Europe, Western Asia 170 cm (5 ft 7 in) 55–70 kg (121–154 lb)

(heavily built) 1,200–1,900 Many 1829

1864

H. floresiensis

classification uncertain 190–50 Indonesia 100 cm (3 ft 3 in) 25 kg (55 lb) 400 7 individuals 2003

2004

Nesher Ramla Homo

classification uncertain 140–120 Israel several individuals 2021

H. tsaichangensis

possibly H. erectus or Denisova c. 100[s] Taiwan 1 individual 2008(?)

2015

H. luzonensis

c. 67[99][100] Philippines 3 individuals 2007

2019

See also

icon Evolutionary biology portal

List of human evolution fossils (with images)

Multiregional origin of modern humans

Footnotes

The conventional estimate on the age of H. habilis is at roughly 2.1 to 2.3 million years.[1][2] Suggestions for pushing back the age to 2.8 Mya were made in 2015 based on the discovery of a jawbone.[3]

The line to the earliest members of Homo were derived from Australopithecus, a genus that had separated from the chimpanzee–human last common ancestor by late Miocene or early Pliocene times.[4]

Homo erectus in the narrow sense (the Asian species) was extinct by 140,000 years ago; H. erectus soloensis, found in Java, is considered the latest known survival of H. erectus. Formerly dated to as late as 50,000 to 40,000 years ago, a 2011 study pushed the H. e. soloensis extinction date back to 143,000 years ago at the latest, more likely before 550,000 years ago.[6]

The word "human" itself is from Latin humanus, an adjective formed on the root of homo, thought to derive from a Proto-Indo-European word for "earth" reconstructed as *dhǵhem-.[15]

In 1959, Carl Linnaeus was designated as the lectotype for Homo sapiens,[16] which means that following the nomenclatural rules, Homo sapiens was validly defined as the animal species to which Linnaeus belonged.

Cela-Conde & Ayala (2003) recognize five genera within Hominina: Ardipithecus, Australopithecus (including Paranthropus), Homo (including Kenyanthropus), Praeanthropus (including Orrorin), and Sahelanthropus.[36]

In a 2015 phylogenetic study, H. floresiensis was placed with Australopithecus sediba, H. habilis and Dmanisi Man, raising the possibility that the ancestors of H. floresiensis left Africa before the appearance of H. erectus, possibly even becoming the first hominins to do so and evolved further in Asia.[54]

Confirmed H. habilis fossils are dated to between 2.1 and 1.5 million years ago. This date range overlaps with the emergence of Homo erectus.[83][84]

Hominins with "proto-Homo" traits may have lived as early as 2.8 million years ago, as suggested by a fossil jawbone classified as transitional between Australopithecus and Homo discovered in 2015.

A species proposed in 2010 based on the fossil remains of three individuals dated between 1.9 and 0.6 million years ago. The same fossils were also classified as H. habilis, H. ergaster or Australopithecus by other anthropologists.

H. erectus may have appeared some 2 million years ago. Fossils dated to as much as 1.8 million years ago have been found both in Africa and in Southeast Asia, and the oldest fossils by a narrow margin (1.85 to 1.77 million years ago) were found in the Caucasus, so that it is unclear whether H. erectus emerged in Africa and migrated to Eurasia, or if, conversely, it evolved in Eurasia and migrated back to Africa.

Homo erectus soloensis, found in Java, is considered the latest known survival of H. erectus. Formerly dated to as late as 50,000 to 40,000 years ago, a 2011 study pushed back the date of its extinction of H. e. soloensis to 143,000 years ago at the latest, more likely before 550,000 years ago. [88]

Now also included in H. erectus are Peking Man (formerly Sinanthropus pekinensis) and Java Man (formerly Pithecanthropus erectus).

H. erectus is now grouped into various subspecies, including Homo erectus erectus, Homo erectus yuanmouensis, Homo erectus lantianensis, Homo erectus nankinensis, Homo erectus pekinensis, Homo erectus palaeojavanicus, Homo erectus soloensis, Homo erectus tautavelensis, Homo erectus georgicus. The distinction from descendant species such as Homo ergaster, Homo floresiensis, Homo antecessor, Homo heidelbergensis and indeed Homo sapiens is not entirely clear.

The type fossil is Mauer 1, dated to ca. 0.6 million years ago. The transition from H. heidelbergensis to H. neanderthalensis between 300 and 243 thousand years ago is conventional, and makes use of the fact that there is no known fossil in this period. Examples of H. heidelbergensis are fossils found at Bilzingsleben (also classified as Homo erectus bilzingslebensis).

The age of H. sapiens has long been assumed to be close to 200,000 years, but since 2017 there have been a number of suggestions extending this time to as high as 300,000 years. In 2017, fossils found in Jebel Irhoud (Morocco) suggest that Homo sapiens may have speciated by as early as 315,000 years ago.[94] Genetic evidence has been adduced for an age of roughly 270,000 years.[95]

provisional names Homo sp. Altai or Homo sapiens ssp. Denisova.

The first humans with "proto-Neanderthal traits" lived in Eurasia as early as 0.6 to 0.35 million years ago (classified as H. heidelbergensis, also called a chronospecies because it represents a chronological grouping rather than being based on clear morphological distinctions from either H. erectus or H. neanderthalensis). There is a fossil gap in Europe between 300 and 243 kya, and by convention, fossils younger than 243 kya are called "Neanderthal".[97]

younger than 450 kya, either between 190–130 or between 70–10 kya[98]

The argument presented against the hypothesis of Homo sapiens interbreeding with Neanderthals or Denisovans rests on a few central premises and assumptions. Let’s break them down and address counterarguments:

---

### **1. Biological Species Concept**

The biological species concept (BSC) defines species as groups of organisms that can interbreed and produce fertile offspring. The argument suggests that if Neanderthals were a separate species, they would not have been able to produce fertile offspring with Homo sapiens. This is contrasted with examples from other genera, like Equus (horses and donkeys producing sterile mules).

**Counterarguments:**

- The BSC is not universally applicable to all organisms, especially those with complex evolutionary histories. Hybridization can and does occur between closely related species, resulting in fertile offspring in some cases. Examples include:

- **Canids (wolves, dogs, coyotes):** Interbreeding between species produces fertile hybrids.

- **Ursids (grizzly and polar bears):** These species can interbreed and produce viable offspring.

- Genetic evidence clearly shows the presence of Neanderthal and Denisovan DNA in modern Homo sapiens populations. For example:

- ~1–2% of the genome of non-African populations contains Neanderthal DNA.

- Up to 5% of the genomes of some populations in Oceania contain Denisovan DNA.

- These findings suggest that Neanderthals and Denisovans were sufficiently genetically compatible with Homo sapiens to produce fertile offspring, aligning more with a model of subspecies or closely related species.

---

### **2. Fossil Evidence**

The argument claims that evidence of hybrids would be limited to bones or fossils of such individuals, and modern populations could not retain genetic material from separate species.

**Counterarguments:**

- The study of ancient DNA has revolutionized our understanding of human evolution. Fossil evidence alone is not required to confirm interbreeding. Genetic data extracted from ancient remains and compared to modern human genomes directly demonstrate interbreeding.

- Examples:

- The sequencing of Neanderthal genomes and their comparison with modern human DNA has explicitly identified shared genetic markers.

- Ancient hybrids, like the individual known as "Denny," a first-generation offspring of a Neanderthal and a Denisovan, provide direct evidence of interbreeding.

---

### **3. Neanderthals as a Race, Not a Separate Species**

The argument posits that Neanderthals were a variant or subspecies of Homo sapiens rather than a separate species.

**Counterarguments:**

- The classification of Neanderthals as a subspecies (Homo sapiens neanderthalensis) versus a separate species (Homo neanderthalensis) is still debated among scientists. However:

- Regardless of classification, the genetic evidence supports interbreeding and gene flow between populations.

- Distinctive Neanderthal traits, such as adaptations to cold climates, are found in their genome but also persist in modern human populations in certain forms (e.g., genes associated with skin and hair characteristics, immune responses).

- The presence of interbreeding does not necessarily negate their status as a distinct species or subspecies—it underscores the complexity of human evolution.

---

### **4. Waste of Public Funds**

The argument suggests that researching interbreeding between Neanderthals and Homo sapiens is a waste of resources.

**Counterarguments:**

- Understanding interbreeding deepens our knowledge of human history, adaptation, and evolution.

- Genes inherited from Neanderthals contribute to traits like immunity and susceptibility to certain diseases in modern humans.

- Research into these genes has practical implications, such as understanding immune responses and environmental adaptations.

- Scientific inquiry into human origins is a fundamental pursuit that informs anthropology, genetics, and biology, providing context for human diversity and shared heritage.

---

### **Conclusion**

The argument that Neanderthals were merely a variant of Homo sapiens and that interbreeding is implausible contradicts robust genetic evidence. While it is true that species definitions are complex and often blurred, the overwhelming consensus in anthropology and genetics is that interbreeding occurred, leaving a tangible genetic legacy in modern populations. Far from being a waste of resources, studying these phenomena enhances our understanding of humanity's interconnected and adaptive past.

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Mikel Alberto de Elguezabal Méndez-Rodulfo, Montpellier 1977, Cumaná 1979-2013, Navarre since 2013. Biologist. Believer.

LEA Foundation

Cumaná, Sucre

Erratzu, Navarre

@eguraproject

@bioecorganic

@congressliberty

EUSKAL HERRIA DEELGUEZABAL

lunes, 13 de octubre de 2025

Homo sapiens sapiens species

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