Neanderthal DNA Issues

http://www.councilforresponsiblegenetics.org/GeneWatch/GeneWatchPage.aspx?pageId=267


NEANDERTHAL GENES, RELIGION, AND THE UNIQUE IDENTITY OF MODERN HUMANS

By Terence D. Keel




The recent discovery by the Neanderthal Genome Project that present day Europeans and Asians might be the only two populations in possession of Neanderthal DNA forces us to yet again ponder the relationship between genetics and human identity. Who we think we are has much to do with the questions we ask. And for Homo sapiens there are perhaps no greater questions of ultimate concern than "where do we come from" and "what makes a human, human?" Increasingly genetics offers tools to trace our roots, and the genetic ancestry industry has flourished due to growing public interest in what has been packaged as "racial" diversity (what geneticists call "admixture") within our DNA.1 So far, genetic identity testing technologies have been able to trace human origins back to the continental regions where ancestors of modern humans left Africa somewhere between 50,000 and 100,000 years ago and branched into the various populations often thought of as "races." But lately, figuring out what makes us human appears to be a moving target.

Recent news that on average "Europeans" and "Asians" may possess up to 4% Neanderthal DNA not only reveals previously unknown genetic admixture, it pushes us to reframe the distinction between non-human and human descent. Geneticist Svante Pääbo, from the Neanderthal Genome Project, seemed to suggest this as he was reported saying, "Neanderthals are not totally extinct; they live on in some of us."2 With this new information the quest for the genetic "admixture" of modern humans has now formally extended beyond racially "mixed" family trees and into the "pre-historic" age. Some of our perceptions about the purity of our inherited genetic legacy will be altered now that many of us might be related to hominids from the Land of the Lost.

In the U.S., we have largely come to believe that science and religion (or specifically evolutionary biology and Christianity) offer strikingly different answers to the question of our beginnings. This is no doubt true if the conversation solely concerns whether humans were the direct and instantaneous creation of God or evolved precariously from a lowly anthropoid ancestor. The lines between religion and science on the issue of human origins become blurred, however, when the question is framed in terms of what essential attributes make us "human." That is, what are the specific physical and intellectual traits that decisively demarcate modern humans from non-human species?

For centuries Christian philosophers like St. Augustine and Thomas Aquinas turned to the human capacity for reason and moral responsibility to illustrate "Man's" uniqueness. Likewise, within the legacy of modern science, natural historians and anthropologists compared the cranial structures, social behavior, and linguistic abilities of humans with those of primates to demonstrate the gulf between us and the animal world. More recently, population geneticists have sought proof of our biological uniqueness by deciphering human gene expressions involved in language, reasoning and brain development not found in other primates.3 If we think about the search for evidence of interbreeding between modern humans and Neanderthals with this history in mind, then it appears that Western scientists and Christian thinkers have shared a commitment to pursuing and detailing the "traits" that corroborate our cultured belief in the uniqueness of our species.

In order to determine what "traits" humans and Neanderthals have in common, the Neanderthal Genome Project used full genome sequencing technology that entailed scanning 60% of the Neanderthal genome.4 They also took up a comparative study of variants in autosomal regions (SNPs)-a technique used in admixture testing-of five people from China, France, Papua New Guinea, South Africa and West Africa with that of the Neanderthal.5 By comparing segments of DNA where SNPs occur at high frequencies in different populations, geneticists were able to discover that Europeans and Asians share up to 4% of their DNA with cavewomen found in Croatia (the fossil samples used in the study were from female Neanderthals). With this geneticists had announced that the line between the human and non-human-crucial to religious and scientific beliefs about the novelty of our species-was in fact more porous than we thought.

Of course this is not the first time that scientific investigations into human descent disrupted the line between human and non-human ancestry, and with it belief in the uniqueness of our species. In the mid 19th century, before Darwin challenged the world to consider humans had descended from primates, a significant debate developed over whether or not present day humans were the offspring of a shared ancestor (monogenesis) or whether the various "races" possessed their own exclusive forbearers (polygenesis). Out of this debate emerged an idea called "pre-Adamite theory" which claimed that Africans, Asians, and Native American populations were "pre-humanoid forms" created separately from Europeans and with no ties to "Adam's" ancestral linage- thought to be the exclusive inheritance of whites.6 For people in the mid-19th century it was a foregone conclusion that Adam was the "original man," but this belief had to be squared with 19th century geological discoveries that increased the age of the earth and challenged the account of creation found in the Christian bible. It also had to be reconciled with data from American ethnologists like Samuel Morton and Josiah C. Nott who claimed that "the races" were utterly different human types. Pre-Adamite theory thus became a useful strategy to account for the perceived intellectual, cranial, linguistic, and moral discrepancies between European and non-European populations, while also maintaining the veracity of biblical knowledge. Moreover, it proved effective for drawing the line between which populations were or were not truly "human." The theory gained increased currency among scientific and religious notables of the day with figures such as the Swiss naturalist Louis Agassiz and Christian modernists Isabelle Duncan and James Gall.

If much of this sounds absurdly distant to modern readers it is because the gradual acceptance of Darwinian biology during the early 20th century and, later, the development of the "Out of Africa" hypothesis put a moratorium on most pre-Adamite ideas. Yet the synthesis of Darwinian biology and evolutionary genetics did not entirely bring an end to the debate between monogenists and polygenists over the shared ancestry of all modern day humans. During the late 1980's, a group of geneticists led by Milford H. Wolpoff proposed a "multiregional hypothesis" as an alternative explanation to the "Out of Africa" theory.7 This multiregional model suggested that modern day humans did not evolve solely from the group of early humans who migrated out of Africa between 50,000 and 100,000 years ago. Wolpoff's group wanted to say that humans might have also evolved from other ancestral hominids living in regions outside of Africa already.8

Recent blogosphere and public reactions to the discovery of Neanderthal admixture in some humans but not others has potentially brought new life to old debates over the multiple origins of the various races that echo concerns voiced by 19th century proponents of pre-Adamite theory.

A number of social conservatives have played up the fact that Europeans, rather than Africans, possess Neanderthal DNA. Just days after the discovery of the Neanderthal genome a majority of bloggers on the white supremacist website Stormfront.org congratulated themselves for their genetic uniqueness and claimed Neanderthal DNA was responsible for the "intellectual supremacy" and "physical prowess" of Europeans. Several even shared the sentiment conveyed by an anonymous blogger who suggested that:

"[As] Neanderthal genes become more inundated with other racial mixes we have been evolving back wards [sic]. It may be that in a few hundred years so little will remain of these genes that we will be inseparable from the lower form of human (i.e. blacks)."9

Interestingly, white supremacists have understood their genetic bond with the evolutionarily primitive Neanderthal as a mark of lauded genetic distinction and biological superiority. We can see here how the idea that human life began in Africa doesn't preclude beliefs about the biological inferiority of present day African populations.

It is clear from Creationist blogs that explicit belief in pre-Adamites is a thing of the past for those Christians who firmly believe in the common ancestry of all humans. However, it seems that Creationist bloggers have taken the recent discovery about "pre-human" DNA within our bloodlines to redraw the distinction between humans and non-humans. In fact several Creationist claim Neanderthals are fully human.10 Creationists have contended that paleontologists have fabricated the very idea of the Neanderthal, deliberately mixing the fossil remains of an ancient human with primates in order to justify the evolutionary belief in a creature not quite animal nor fully human.11 Creationists have insisted that our recent genetic ties to the Neanderthal should force us to abandon scientific theories that claim humans have genetic material that make them a "new" and separate species from this ancestral hominid.12

Listeners' reaction to NPR's coverage of the Neanderthal Genome Project were a bit more measured, but inevitably concerns similar to those expressed by the Creationists and Stormfront bloggers were peppered throughout the discussion.13 One anonymous listener was concerned by the lack of attention given to "the six day creation model and how it better answers the questions of our origin than evolution." Others shared his reaction that pro-evolutionists have "the political power" to "suppress any discussion of an alternative model." Creative efforts were also made to rethink the Genesis creation story in light of this new finding, as one listener suggested that perhaps

"Adam and Eve were the first cognizant humans, their two offshoots- offspring were Neandethal son Abel and Modern or Cro Magnan son Cain. Abel the hunter, Cain the planter. And Cain killed off his brother Abel. It's a terrible story of why there are no Neanderthals today."

Several listeners speculated that the Neanderthal genome was possibly responsible for the "red hair", "blue eyes" "stocky stature, long torso" and other phenotypes expressed exclusively by "whites." Another listener interested in the implications this discovery has for thinking about racial differences claimed that:

"[The fact that] Neanderthal genes are distributed globally yet not much among African people hints at the possibility of a genetic explanation for racism ,,, Perhaps over time, Neanderthal genes made their carriers wary and fearful of hominids who looked unlike them and shared fewer of those genes. After all, it seems that anti-black feelings run deepest in Eurasia and Asia, where the Neanderthal carriers ended up."

Continuing in the spirit of pondering what the Neanderthal genome means for thinking about race, one listener raised an important question regarding the distribution of Neanderthal DNA in a racially intermixed country like America. The question was:

"If Neanderthals mated with non- Africans, but throughout history Non-Africans have been mating with Africans esp [sic] in America, would this mean that only Africans who are in Africa whose ancestors had no contact or mated with only other Africans would only have there [sic] genomes be pure from Neanderthals' DNA? As opposed to ones who have white ancestor in them?"

What does this discovery mean for populations with partial European ancestry? Might these groups also possess Neanderthal DNA? Interestingly, ancestry-testing specialists estimate that, on average, African Americans posses 18.5 % European DNA.14 This potentially means that if you were to compare the full genomes of African- Americans with the Neanderthal it is likely that many would also have genetic ties to this ancestral hominid.

Given these public reactions it seems that knowledge of the interbreeding between humans and Neanderthals has shaken up what many believe constitutes the modern human and has also provided new data for thinking about the novelty of our species. It also appears to be the case that discussions about the Neanderthal genome inevitably animate concerns about racial difference and religious claims about human origins. It is as though science, religious belief, and ideas about race share a deep and unspoken bond made explicit when knowledge about the uniqueness of our species is called into question. Yet, in an interesting way, the Neanderthal genome presents us with a telling reversal of history where having "pre-Adamite" relatives might just be a mark of distinction-rather than inferiority.

But before labs start direct-to-consumer testing for Neanderthal DNA we have to keep a couple of things in mind. Additional genomic sequences to verify the findings of the Neanderthal Genome Project have yet to be made, and the Project claims only to have constructed a "draft" of the Neanderthal genome. Nevertheless, these limitations haven't prevented excitement around this discovery, as it appears that the Neanderthal DNA within present day humans was positively selected.15 This is to say that the DNA acquired from Neanderthals once provided functional advantages to our human ancestors. Large bodies, big brains, and plenty of aggression were surely valuable attributes in pre-historic times. However, geneticists have also discovered that Neanderthal DNA within present day humans seems associated with metabolic and cognitive functions that cause diabetes, Down Syndrome, Autism and Schizophrenia.16

Geneticists still have not ruled out whether African populations also possess ancestral hominid DNA-much like the Neanderthal discovered in Croatia- hidden somewhere between the 3 billion DNA base pairs that make up their genetic identity. Humans could have mated with ancient hominids prior to the "Out of Africa" event and we just haven't found their fossil remains. Nor is it clear if blacks with European ancestry in the Caribbean, South America or other parts of the African Diaspora also posses Neanderthal DNA. Even though their discovery emphasized European and Asian possession of Neanderthal DNA, the authors of the study were careful to say that, "Neanderthals are closer to non-Africans than to Africans." The key here is to understand that people of African descent are not necessarily devoid of Neanderthal DNA. Rather there are degrees of separation or, depending on how you see it, connection between all groups and this ancestral hominid.

Ultimately, the presence of Neanderthal DNA-or any other ancestral hominid-within a living person today merely offers us a new lens for an ever-broadening understanding of our genetic diversity and our species identity. This should ultimately be embraced as yet another testament to the collective uniqueness of the human race.



Terence D. Keel is a PhD candidate in the program on Religion and Society at Harvard University.



Endnotes

1. For more on how ancestry technologies conceptualize race see Duana Fullwiley’s work “The Biologistical Construction of Race: ‘Admixture’ Technology and the New Genetic Medicine in, Social Studies of Science Vol. 38, No. 5 October 2008, pp. 700-706.
2. Tina Hesman Saey, “Neanderthal genome yields evidence of interbreeding with humans” in, Science News Vol. 177, No. 12, June 5, 2010.
3. To understand, for example, how the “HAR1F” gene is thought to have played a crucial role in shaping our distinctly human brain see, Katherine S. Pollard et al, “An RNA gene expressed during cortical development evolved rapidly in humans” in, Nature Vol. 443, September 2006, pp. 167-172. For a more recent discovery see Xiaoquing Zhang et al, “Pax6 Is a Human Neuroectoderm Cell Fate Determinant”
in, Cell Stem Cell Vol. 7, No. 1, July 2010, pp. 90-100.
4. Richard Green, et al “A Draft Sequence of the Neanderthal Genome” in, Science Vol. 328, May 2010, pp. 710.
5. Ibid 720.
6. David N. Livingstone, Adam’s Ancestors: Race, Religion, and the Politics of Human Origins (Baltimore: John Hopkins University Press, 2008), pp.80-108.
7. Milford H. Wolpoff, et al “Modern Human Origins” in, Science Vol. 241, No. 4867, August 1988, pp. 772-774.
8. Milford H. Wolpoff, et al “Multiregional, not multiple origins” in, American Journal of Physical Anthropology Vol. 12, No. 1, April 2000, pp. 129-136.
9. See Stromfront thread, “How there’s a bit of Neanderthal in all of us: DNA link to cavemen revealed” May 6, 2010: http://www.stormfront.org/forum/t706174/.
10. See Ian Juby’s blog entry “whadya know: Neanderthals are human!” in the Creation Science Newsletter, May 6, 2010: http://ianjuby.org/newsletter/?p=360.
11. For a more thorough understanding of the Creationist critique of evolutionary theory and belief in the existence of the Neanderthal see the thought of Sean D. Pitman in, The Evolution of Early Man October 2005: http://www.detectingdesign.com/earlyman.html#Table%20of%20Contents.
Also see Ian Juby’s blog entry, “ ‘The Evolution of evolution’: a response to the January 2009 Scientific American”: http://ianjuby.org/jan2009sciam2.html#pedigree .
12. See Sean D. Pitmann, “Neanderthal” in, The Evolution of Early Man October 2005:
http://www.detectingdesign.com/earlyman.html#Neanderthal.
13. See the public thread from On Point with Tom Ashbrook, “Neanderthals: Our Kissing Cousins?” May 13, 2010 http://www.onpointradio.org/2010/05/neanderthals-our-kissing
14. Sarah Tishkoff, “Genome-wide patterns of population structure and admixture in West Africans and African Americans” in, Proceedings of the National Academy of Sciences of United States Vol. 107 No. 2, 2010, 786-791.
15. Green, et al, pp. 716-717.
16. Ibid, pp. 717.