Changes for page The Existence of Race

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17	17	== Neanderthal Admixture and Its Implications for Human Racial Classification ==
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19		-The classification of Neanderthals as a separate species or subspecies from modern humans (*Homo sapiens*) has long been a subject of scientific debate. Traditionally, Neanderthals were considered a distinct species (*Homo neanderthalensis*) based on morphological differences in skeletal remains. These include features such as a more robust build, larger cranial capacity, prominent brow ridges, and a distinct facial structure. However, advances in paleogenetics and ancient DNA analysis have complicated this clear-cut distinction.
	19	+The taxonomic status of Neanderthals has long been debated, traditionally classified as a distinct species, *Homo neanderthalensis*, based on notable morphological differences from modern humans (*Homo sapiens*). These differences include a more robust skeletal build, larger cranial capacity, pronounced brow ridges, and distinct facial features. However, advances in ancient DNA sequencing and paleogenetics have complicated this view by revealing evidence of gene flow between Neanderthals and anatomically modern humans.
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21	21	=== Morphological Distinctions ===
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23		-Neanderthals exhibit several skeletal traits that differentiate them from anatomically modern humans, including:
	23	+Neanderthals are characterized by several skeletal features that distinguish them from modern humans: they have larger, elongated cranial vaults with a projecting midface, prominent supraorbital ridges (brow ridges), wider noses with larger nasal cavities, shorter and stockier limbs adapted for cold climates, and an overall robust skeletal morphology. While these traits are significant, many overlap with the range of variation found within some modern human populations, particularly among archaic or robust groups, making strict morphological delineation challenging.{{footnote}}Green, Richard E., et al., "A Draft Sequence of the Neandertal Genome," *Science* 328(5979): 710–722 (2010). Available at: [[https://www.science.org/doi/10.1126/science.1188021]]{{/footnote}} {{footnote}}Prüfer, Kay, et al., "The complete genome sequence of a Neanderthal from the Altai Mountains," *Nature* 505: 43–49 (2014). Available at: [[https://www.nature.com/articles/nature12886]]{{/footnote}}
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25		-* Larger, elongated cranial vaults but with a more projecting midface.
26		-* Prominent supraorbital ridges (brow ridges).
27		-* Wider noses and larger nasal cavities.
28		-* Shorter, stockier limbs adapted for cold climates.
29		-* Robust overall skeletal morphology.
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31		-While these differences are significant, they are not so drastic as to make Neanderthals unambiguously non-human. In fact, many of these features overlap with variation seen within modern human populations, particularly among certain archaic or robust groups. This phenotypic overlap complicates classification purely on morphological grounds.{{footnote}}Green, Richard E., et al., "A Draft Sequence of the Neandertal Genome," *Science* 328(5979): 710–722 (2010). Available at: [[https://www.science.org/doi/10.1126/science.1188021]]{{/footnote}} {{footnote}}Prüfer, Kay, et al., "The complete genome sequence of a Neanderthal from the Altai Mountains," *Nature* 505: 43–49 (2014). Available at: [[https://www.nature.com/articles/nature12886]]{{/footnote}}
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33	33	=== Genetic Evidence and Interbreeding ===
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35		-A pivotal discovery in the early 21st century was the sequencing of Neanderthal nuclear DNA, which revealed that non-African modern humans carry approximately 1–4% Neanderthal-derived genetic material. This finding implies that Neanderthals and modern humans interbred after modern humans migrated out of Africa roughly 50–70 thousand years ago.{{footnote}}Green, Richard E., et al., "A Draft Sequence of the Neandertal Genome," *Science* 328(5979): 710–722 (2010). Available at: [[https://www.science.org/doi/10.1126/science.1188021]]{{/footnote}} {{footnote}}Reich, David, et al., "Denisova admixture and the first modern human dispersals into Southeast Asia and Oceania," *American Journal of Human Genetics* 89(4): 516–528 (2011). Available at: [[https://www.cell.com/ajhg/fulltext/S0002-9297(11)00364-2]]{{/footnote}}
	27	+Genomic analyses have established that non-African modern humans possess approximately 1–4% Neanderthal-derived DNA, indicating that interbreeding occurred after modern humans migrated out of Africa around 50,000 to 70,000 years ago.{{footnote}}Green, Richard E., et al., "A Draft Sequence of the Neandertal Genome," *Science* 328(5979): 710–722 (2010). Available at: [[https://www.science.org/doi/10.1126/science.1188021]]{{/footnote}} {{footnote}}Reich, David, et al., "Denisova admixture and the first modern human dispersals into Southeast Asia and Oceania," *American Journal of Human Genetics* 89(4): 516–528 (2011). Available at: [[https://www.cell.com/ajhg/fulltext/S0002-9297(11)00364-2]]{{/footnote}} This gene flow indicates reproductive compatibility, producing fertile offspring, which aligns with the biological species concept where species boundaries are defined by reproductive isolation. Consequently, many researchers argue that Neanderthals may be more accurately considered a subspecies or regional population within a broader *Homo sapiens* species complex rather than a completely separate species.{{footnote}}Pääbo, Svante, "The human condition—a molecular approach," *Cell* 157(1): 216–226 (2014). Available at: [[https://www.cell.com/fulltext/S0092-8674(14)00267-2]]{{/footnote}} {{footnote}}Coyne, Jerry A. and H. Allen Orr, *Speciation*, Sinauer Associates, 2004.{{/footnote}}
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37		-The presence of Neanderthal alleles in modern human genomes challenges the strict species boundary and suggests they were reproductively compatible, producing fertile offspring. This aligns with the biological species concept, which defines species by reproductive isolation. The gene flow indicates that Neanderthals might be better understood as a subspecies or a population within a broader species complex rather than a fully distinct species.{{footnote}}Pääbo, Svante, "The human condition—a molecular approach," *Cell* 157(1): 216–226 (2014). Available at: [[https://www.cell.com/fulltext/S0092-8674(14)00267-2]]{{/footnote}} {{footnote}}Coyne, Jerry A. and H. Allen Orr, *Speciation*, Sinauer Associates, 2004.{{/footnote}}
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39	39	=== Implications for Racial Classification ===
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41		-The Neanderthal-modern human case provides a useful analogy for understanding race in modern humans:
	31	+The Neanderthal-modern human admixture case provides an instructive analogy for modern human racial classification. It demonstrates how gene flow and admixture can blur subspecies or species boundaries. Prior to interbreeding, Neanderthals possessed unique alleles absent in *Homo sapiens*; however, these alleles entered the modern human gene pool through hybridization, eroding strict genetic distinctions. Similarly, human races differ largely in allele frequencies rather than possessing exclusive alleles. Morphological differences between races also overlap continuously without discrete boundaries.
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43		-* Gene flow and admixture blur species or subspecies boundaries: Neanderthals had unique alleles prior to admixture, but those alleles became incorporated into modern human populations through interbreeding. Over time, this genetic mixing erased a clear genetic separation.
	33	+Importantly, the timeline of divergence is key: Neanderthals diverged from modern humans hundreds of thousands of years ago and were largely isolated until admixture events, whereas modern racial groups diverged more recently (tens of thousands of years ago) with ongoing gene flow. Classification decisions—whether based on reproductive isolation, genetic differentiation, or morphology—are inherently human constructs reflecting chosen criteria.
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45		-* Modern human races differ primarily in allele frequency distributions, not in unique alleles: Similar to Neanderthals and modern humans, current human races do not have exclusive alleles absent in others, but rather differences in the relative frequencies of shared genetic variants, shaped by historical separation and partial reproductive isolation.
	35	+Thus, the Neanderthal case supports viewing modern races as meaningful biological clusters within one species, acknowledging partial reproductive isolation and allele frequency differences but no fully unique, fixed genetic boundaries. The blurring of Neanderthal distinctiveness through admixture parallels the fluidity and fuzziness of racial boundaries within *Homo sapiens*.{{footnote}}Sankararaman, Sriram, et al., "The genomic landscape of Neanderthal ancestry in present-day humans," *Nature* 507: 354–357 (2014). Available at: [[https://www.nature.com/articles/nature12961]]{{/footnote}} {{footnote}}Vernot, Benjamin and Joshua M. Akey, "Resurrecting surviving Neandertal lineages from modern human genomes," *Science* 343(6174): 1017–1021 (2014). Available at: [[https://science.sciencemag.org/content/343/6174/1017]]{{/footnote}}
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47		-* Time scale matters: Neanderthals diverged from modern humans hundreds of thousands of years ago and remained largely isolated until interbreeding events. Modern human racial groups diverged more recently (tens of thousands of years) with varying levels of gene flow.
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49		-* Morphological distinctions can overlap across groups: Just as Neanderthal skeletal traits show overlap with modern humans, racial differences in morphology exhibit continuous variation without discrete boundaries.
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51		-* Classification is inherently a human decision based on criteria: Whether Neanderthals are designated a species or subspecies depends on taxonomic philosophy, which applies similarly to how races are classified biologically.
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53		-Thus, if the ability to interbreed and genetic continuity is key to species or subspecies designation, the absorption of Neanderthal alleles into modern humans reflects a collapse of their distinct classification. Similarly, modern races, while showing differences, exist within one species with partial but incomplete reproductive isolation.
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55		-* Neanderthals exhibit notable but overlapping morphological differences from modern humans.
56		-* Genetic evidence confirms interbreeding and gene flow between Neanderthals and modern humans.
57		-* This admixture weakens the species boundary, supporting subspecies or population-level classification.
58		-* Modern human racial groups similarly show partial isolation with distinct allele frequencies, but no fully unique alleles.
59		-* The Neanderthal case underscores the complexities in classifying biological groups and supports viewing human races as meaningful, though not absolute, biological clusters.
60		-
61	61	== Genetic Evidence for Human Races ==
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63	63	With the advent of genetics, researchers can directly examine human population structure. Modern genomic studies have repeatedly found that human genetic variation is not a homogeneous blur, but rather clusters into discernible groups corresponding to traditional racial categories and geographic ancestry.{{footnote}}Jerry Coyne, "Once again: are 'races' social constructs without biological meaning?" *Why Evolution Is True* blog, July 19, 2022. Available at: [[https://whyevolutionistrue.com/2022/07/19/once-again-are-races-social-constructs-without-scientific-or-biological-meaning/#:~:text=,And%20Me%20stay%20in%20business]]{{/footnote}} Notably, in a landmark analysis of over 3,600 individuals from around the world, genetic clustering algorithms could sort people into distinct groups (clusters) that correspond almost perfectly to self-identified race/ethnicity. In that study, *over 99%* of individuals were genetically classified into the same group as their self-declared race (only 5 out of 3,636 were exceptions). Such findings directly refute the notion that race is purely arbitrary; instead, they show that an individual’s continental ancestry can be determined from DNA with over 99% accuracy in these samples.{{footnote}}Tang, Hua et al. *“Genetic structure, self-identified race/ethnicity, and confounding in case-control association studies.”* American Journal of Human Genetics 76(2): 268–275 (2005) – (Found that genetic clusters correspond 99.86% with self-identified race in a US sample). Available at https://www.sciencedirect.com/science/article/pii/S0002929707625786{{/footnote}}