Feb 16 2009

Neanderthal Genome

Scientists have completed a “first draft” of the neanderthal genome. This is exciting on many levels. One of the burning questions of paleoanthropology is the relationship between humans and our closest cousins, the Homo neanderthalensis. Debate has gone back and forth over years, but this is a debate that can be resolved with evidence.

So now that we have taken a good peek at the neanderthal genome, what do we find? Svante Paabo, speaking at the AAAS, reports that his team could not find any evidence of interbreeding between neanderthals and humans. This does not mean there was absolutely no cross-species hanky panky, but it does mean that it was rare and contributed minimally to the human genome. There still might be a mutation or two to be found contributed to the human genome from neanderthals – or contributed to the neanderthals from humans. But the big question has been answered – the two populations did not merge.

We know that neanderthals and early Homo sapiens co-existed in Europe for thousands of years. We are extremely close genetically, sharing >99% of our genome and having the same number of chromosomes, so humans and neanderthals would almost certainly have been able to breed and have fertile young. We also know that humans survived and spread throughout the world, while neanderthals became extinct about 30,000 years ago.

This fact has led to another burning question – why did they go extinct. The Darwinian bias is to think that they were unfit in some way, or were outcompeted or perhaps hunted to extinction by humans. This may be correct, and competition (in the absence of interbreeding) probably played some role. But it is interesting how deeply the “fitness” bias runs. I have seen dozens of documentaries on evolution, and it seems the running commentary cannot help to portray new emerging species as better and stronger, and species on the way out as feeble and inferior.

Rather, most species are just adapted to their local environment. The most common respnose to a changing environment is to migrate – habitat tracking. When that fails, the second most common response is extinction. Speciations tends to occur in small subpopulations on the fringes of a species’ range. Most species that go extinct were just unlucky – their environment changed and they could not migrate to a similar environment.

Humans are therefore not inherently superior to neanderthals just because we survived and they didn’t. However, having said that – there is independent evidence (other than the mere fact of our survival) that humans did have skills neanderthals lacks. Our tools were more sophisticated, and human tribes had a division of labor that may have made them more efficient. Also, only humans left behind evidence of art. There is no neanderthal art. From this we might infer a more nimble or expansive intellect.

But the truth is, we don’t really know. This remains an area of investigation and researchers are slowly exploring not only how humans and neanderthals differed, but how those differences may have related to differential survival. It is not always as simple as it may seem to make this connection.

Another question that has arisen as a consequence of sequencing the neanderthal genome is the possibility of cloning a neanderthal. While Paabo and others are saying this is not possible anytime soon – it eventually will be. We are already working on cloning the mammoth and recently extinct species like the Tasmanian tiger. One of the factors that affects how easy or difficult it will be to clone an extinct species is whether or not they have a close living relative – the closer the better. Mammoths have elephants.

Well, neanderthals have humans. I already stated that there is little difference between the human and neanderthal genomes. If we identify all those difference we could then close a neanderthal from a human by making the necessary changes. While it is difficult to say how long it will take for this technology to emerge, it is almost an inevitability. It will happen sooner or later.

Then, of course, the real question becomes one of ethics. The ethical issues will probably take much longer to work out than the technical ones.

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19 responses so far

19 Responses to “Neanderthal Genome”

  1. Michael Meadonon 16 Feb 2009 at 9:17 am

    Interesting post Steve, thanks…

    I saw Paabo quoted somewhere (New Scientist, I think) saying it will be impossible to clone a Neanderthal. I’m not sure why he’d say that, since, yes, they have humans to act as surrogates. While the scientific payoff of such a resurrection would no doubt be immense, the ethics would be enormously difficult to settle. Besides, look at all the problems we Homo sapiens have had with racism – imagine speciesism.

    My 2 (Zimbabwean) cents, anyway.

  2. daedalus2uon 16 Feb 2009 at 10:40 am

    This is very interesting. Especially if Neanderthal were physically able to breed with humans and it didn’t happen, there must have been some pretty powerful psychological mechanisms to prevent that. There is a phenomena called “the uncanny valley”.

    http://en.wikipedia.org/wiki/Uncanny_valley

    Where if a humanoid is too close to being human it elicits revulsion. I suspect this occurs by triggering a “xenophobia” module. Neanderthal may be the species that this xenophobia module evolved to elicit revulsion toward. If Neanderthals specifically trigger xenophobia, cloning a Neanderthal will be problematic.

    That might be testable because there are some human populations that likely were not exposed to Neanderthal; humans in Africa likely had no exposure, and so different features might have different capacities to trigger xenophobia.

  3. deciuson 16 Feb 2009 at 12:27 pm

    PZ Myers has expressed some reservations over this announcement, pointing out that it is a case of science by press release, for there is no paper yet.

    Furthermore, the sample comes from a single specimen and some degradation is to be expected, while a 60% sequencing probably provides more questions then answers.

    I’ll get me coat.

  4. deciuson 16 Feb 2009 at 12:31 pm

    “Then” should read “than”, sorry.

  5. HHCon 16 Feb 2009 at 2:15 pm

    Its interesting to follow the Neanderthal to Human story. A few years back, mtDNA from Neanderthal bones had little relationship to modern humans. Professor Paabo, using nuclear DNA is studying one gene of speech and language, FOXP2. It had been theorized that humans contributed to the gene pool of Neanderthals. My hypothesis would be that the male human,e.g. from Croatia or Africa was attracted to a Neanderthal female. The Neanderthal female had a smaller skull than the male. The female could share her genes with an early human descendant.

  6. HHCon 16 Feb 2009 at 2:34 pm

    The theory of Uncanny valley would be best applied to the ballet, Coppelia or La Fille Aux Yeux D’Email by Leo Delibes. The dehumanized doll was loved by the male dollmaker because of her beauty and dancelike movements.

  7. MBoazon 16 Feb 2009 at 2:38 pm

    So no freaky-deaky cave man sex? That’s disappointing.

  8. DevilsAdvocateon 16 Feb 2009 at 3:31 pm

    Neanderthal? I mean, I’ve heard of ‘getting a little strange’, but…

  9. daedalus2uon 16 Feb 2009 at 3:32 pm

    Growing Neanderthal cells in tissue culture doesn’t pose the ethical issues of trying to grow intact Neanderthal.

    Neanderthal mitochondrial DNA could (probably) be used to recreate Neanderthal mitochondria. Those mitochondria could be used in human cells to create chimeric cells with Neanderthal mitochondria and human nuclear DNA. If those cells are not viable, then human males and Neanderthal females could not reproduce.

    The same could be done the other way (once Neanderthal cells were available in tissue culture). If cells with a Neanderthal nuclear DNA and human mitochondria were not viable, then human females and Neanderthal males could not reproduce either.

    This technique has been used in some rodent species.

    In thinking more about xenophobia, that would have to exist before the species came into contact, it couldn’t arise after contact or there would be gene transfer before it happened and that would (most likely) remain.

  10. Joeon 16 Feb 2009 at 3:36 pm

    HHC on 16 Feb 2009 at 2:15 pm wrote “My hypothesis would be that the male human,,e.g. from Croatia or Africa was attracted to a Neanderthal female. … The Neanderthal female had a smaller skull than the male. The female could share her genes with an early human descendant.” HHC also wrote “A few years back, mtDNA from Neanderthal bones had little relationship to modern humans. ”

    MtDNA is inherited from female ancestors, so lack of correspondence in mtDNA specifically sheds doubt on the idea that male sapiens bred with female Neanderthals, as you suggest; at least, not on a large scale.

    Statistically, ancestral genes go away (without respect to natural selection). That is why scientists speak of a single, ancestral mother of all humans (dubbed, Eve). She was not the only human female at the time; she is just the only one who still has descendants. The same thing pertains to y-chromosome DNA for male ancestors.

    The bottom line- if there was some, limited interbreeding; it would not be surprising if it does not show up in today’s genome.

  11. HHCon 16 Feb 2009 at 5:23 pm

    When we think about why the Neanderthals disappeared perhaps we could find an analogy to mating with AIDS infected females. If the male Neanderthal mated with a diseased female, whether homo sapien or Neanderthal, the species could not continue the line of descent.

  12. Jim Shaveron 16 Feb 2009 at 6:04 pm

    Steve, in your penultimate paragraph,

    If we identify all those difference we could then close a neanderthal from a human by making the necessary changes.

    I think that should read “…clone a neanderthal…”.

  13. Dan Royon 18 Feb 2009 at 5:39 am

    The current heavyweight champ Valuev leaves me still not fully convinced.
    http://www.thepeoplescube.com/images/Valuev_Boxer.jpg

  14. HHCon 18 Feb 2009 at 9:39 pm

    The Profiles of Valuev versus the Neanderthal:

    2008 Heavyweight champion boxer, Valuev was born in Leningrad,i.e. St. Petersburg, Russia. He stands seven feet tall. His ancestors were Russian and Tartar. He has a large ridged skull and reddish blond brown hair.

    The Neanderthal has been documented at sites throughout Northern Europe. The unique MC1R gene for blond/red hair has been traced to the Neanderthal specimens. However, the Neanderthal has been described as squat, stocky and muscular.
    Profile doesn’t match current champion boxer, Valuev.

  15. Apolloon 19 Feb 2009 at 3:37 am

    “Our tools were more sophisticated, and human tribes had a division of labor that may have made them more efficient. Also, only humans left behind evidence of art. There is no neanderthal art. From this we might infer a more nimble or expansive intellect.”

    I have some reservations about the idea that art should be taken as a sign of intelligence. It seems only to be evidence that our brains are wired to give us slightly different nature. After all modern humans very in their artistic inclinations but we don’t seem to take that as indicative of differing levels of intelligence.

    The difference in our tools is much more compelling, but it still seems possible that it is the result of differences in our nature that do not apply differences in our intelligence. For example, my understanding is that Neanderthals probably lived in small groups with limited interaction with other groups, while Sapiens lived in larger groups and apparently traded with other groups. If this is true, would it not be possible that the difference in technology is a result of the social nature of Neanderthals inhibiting innovation rather than of differences in intelligence at the individual level?

  16. Dan Royon 19 Feb 2009 at 8:47 am

    True. But hey, 5 out of 6 features!
    Until Mr. Valuev undergoes DNA-testing my hopes are up.

  17. HHCon 19 Feb 2009 at 12:40 pm

    Testing a sample of Valuev’s cells to map his DNA would provide a clearer picture of a human or homo sapiens genome. You have to test specific Neanderthal bones to obtain the Neanderthal genome. The Neanderthal is considered to be our closest relative, but these relatives left earth about 18,500 to 24,000 years ago. They endured a climatic Heinrich event (2). They were hardy, surviving 3 to 4 thousand years. Their tools were more efficient, stone flake/blade tools than some of homo sapiens’ culture enriched tools.

    Looks like Valuev is just The Strong Man of Leningrad!

  18. HHCon 20 Feb 2009 at 12:13 pm

    Based on dental records of Neanderthals,i.e. teeth, they were carnivores on a high calorie diet. This led to fast growth and a big brain by age 3 or 4. The fast growth and high mortality were correlated. Human brains progess developmentally at a slower rate. The human arts stimulate young humans to achieve in many areas of human interest.

  19. khepion 23 Feb 2009 at 7:40 pm

    I think it is unlikely that humans and neanderthals did not interbreed. We’ve had trouble keeping it in our pants dating from well before we had pants.

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