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Scientific American

Our Neandertal Brethren

published August 2010 | comments (58)
Genome sequencing has revealed our common humanity
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According to the late Harvard University biologist Ernst W. Mayr, the greatest evolutionary theorist since Charles Darwin, “species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.”

Reproductive isolation is the key to understanding how new species form, and many types of barriers can divide a population and split it into two different groups: geographic (such as a mountain range, desert, ocean or river), morphological (a change in coloration, body type or reproductive organs), behavioral (a change in breeding season, mating calls or courtship actions), and others. After isolation, if members of the split populations encounter one another and cannot produce viable offspring that can themselves later successfully interbreed and produce viable offspring (hybrids such as mules are infertile), then these two populations constitute two different species.

Let’s say that a species migrates out of Africa into Europe around 400,000 years ago and becomes reproductively isolated from its ancestral population for the next 320,000 years. It evolves distinctive anatomical features and adaptations for the colder climes. Moreover, even after other descendants of the original ancestral population move into Europe around 80,000 years ago, the skeletons from both groups show no obvious signs of blended characteristics. Modern scientists classify the creatures as two different species.

Then, however, genetic analysis reveals that members of these two species interbred and produced viable offspring that populated Europe and spread eastward as far as China and Papua New Guinea. By Mayr’s definition, these two interbreeding populations are not two species after all, but two sibling subspecies of the original African species. A subspecies has a characteristic appearance and geographic range, Mayr explains, yet he adds this significant qualifier: “It is a unit of convenience for the taxonomist, but not a unit of evolution.”

Thus it is — revealing the identity of my example — that we must reclassify Homo neanderthalensis as Homo sapiens neanderthalensis, a subspecies of Homo sapiens. A comprehensive and technically sophisticated study published in the May 7 issue of Science, “A Draft Sequence of the Neandertal Genome,” by Max Planck Institute evolutionary anthropologists Richard E. Green, Svante Pääbo and 54 of their colleagues, demonstrates that “between 1 and 4% of the genomes of people in Eurasia are derived from Neandertals” and that “Neandertals are on average closer to individuals in Eurasia than to individuals in Africa.” In fact, the authors note, “a striking observation is that Neandertals are as closely related to a Chinese and Papuan individual as to a French individual…. Thus, the gene flow between Neandertals and modern humans that we detect most likely occurred before the divergence of Europeans, East Asians, and Papuans.” In other words, our anatomically hirsute cousins are actually our genetic brothers.

This modified Out of Africa theory holds that around 400,000 years ago a population of hominids migrated northward through the Middle East and into Europe and parts of western Asia. Between 80,000 and 50,000 years ago another population from the ancestral continent journeyed a similar route into the Eurasian landmass, and there the two populations met and mated. We are their descendants. The Neandertal species did not go extinct, because it was never a separate species; instead population pockets of Neandertals died out around 30,000 years ago, whereas other Neandertal populations survived through interbreeding with their modern human brothers and sisters, who live on to this day.

I always suspected that Neandertals and anatomically modern humans interbred, based on a simple observation: humans are the most sexual of all the primates, willing and able to do it just about anywhere, anytime, with anyone (and even with other species if the Kinsey report is to be believed in its findings about farmhands and their animal charges). Given the viable hybrid offspring that the most diverse members of our species have produced as a result of cultural conjoinings through both ancient migrations and modern travel, one has to suspect that close encounters of the corporeal kind occurred not infrequently in those dark and lonely cave nights over the course of those long-gone millennia.

Now that is a tale worthy of a romantic novel, brought to you by science.

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58 Comments to “Our Neandertal Brethren”

  1. Someone Says:

    O, almost forgot:
    Even is Neanderthals did a lot of breeding with Europeans at the time, that doesn’t mean they live on in modern Europeans, the population was likely almost entirely replaced by newcomers from the Middle East that brought agriculture and the late stone age. So interbreeding earlier on in that same Middle East could have left more traces.

  2. Sally-Anne Lambert Says:

    Last year I was viciously attacked verbally in front of colleagues at university for stating to an English associate-professor that it wasn’t proven that Peking Man – or Neandertal – hadn’t interbred with modern humans. Encountering him again just now, I refrained from suggesting an apology might be in order.

    So thanks Max Planck Institute for the slight vindication, also I’d appreciate a total add-up of genes, more than the grey area percentage.

    Let’s go the whole hog and do some justice to Neanderthal. Leif Ekblad must be pleased too. It’s like the breaking of a dam. Also look out for my ‘Hlingit Word Encyclopedia: The Origin of Copper’ for some of the implications. Time now to see who’s honest, and let’s consider who was right all along too.

    Next step: ban GM.

  3. Michael Says:

    Maybe they evolved from the little green men from Mars and the earth’s environment changed the color of the skin.

  4. Michael Says:

    By the way, maybe they were white and then became African-Americans evolving through the beating of the African sun and dark-tanning the pink-skin Neanderthals?

  5. F Norman Says:

    Let’s think bell curve for a moment… if 1-4% of modern human DNA is from Neanderthal, there must be SOME rare individuals who have more, or have less, than this range. Has anyone thought about testing abberant individuals for a higher percentage?

    If anyone follows Olympic wrestling, there is outstanding wrestler named Alexander Karelin, a 286 pound “freak of nature”, unnaturally strong, and was born weighing a shocking 15 pounds.

    Is it possible he has a higher percentage of neanderthal DNA, or that the neaderthal DNA he does have is manifested in the areas that have made him the most dominating wrestler in Olympic history?

    Google him, read his bio, look at him, and tell me if the thought I have on this isn’t crazy.
    Also, maybe the new Desinova DNA is also at play?

  6. ook Says:

    We’re early in this genetic analysis. I would be willing to wager that much more striking revelations will occur in the coming years and it will be shown that Europeans today have a much higher percentage of Neanderthal DNA than Paabo’s conservative estimate. Europeans almost certainly inherited lack of melanin and red hair from H.Neanderthalis…even if those genes have mutated somewhat in the last 60000 years.

  7. beenatural101 Says:

    Interesting ideas everyone. I saw something above about modern man having domesticated animals and neanderthals not. This is simply not the case. Look at 3 of the main domestic animals we have. The dog, the goat, and the cow. The dog and wolf separated in Europe 135000 years ago according to dna studies. Great! Dogs are evolved from european wolves. “modern” man aka cro magnon showed up on the scene in europe at least 50000 years after that. The cow (aurochs in those days) bovine domestic dna shows a common ancestor between india cattle and western cattle over 100000 years ago. # separate goat lineages go back 200 to 275 thousand years ago. That being said, wear studies of neanderthals mousterian tool technology show many of the tools were used for wood working. Ever try to chase a cow down? Corrals to hold animals are only a small step above a natural bottleneck to drive the hunted into. Just close the ends. Music in africa to this day remains mostly percussion and vocals. Neanderthals are known to have bone flutes and whistles. Perhaps they used them to call animals, or communicate over distance in a hunt. Maybe they were mimicking birds, who knows.

  8. Justin Says:

    Neanderthals and Africans started interbreeding about 70,000 years ago. The African/Neanderthal hybrid that survives emerged from this mixing about 30,000 years ago. Soon after animals were domesticated, agriculture began, metallurgy was discovered, cities formed, mathematics began and our written history started. For 400,000 years neither the Neanderthals or the Africans had been able to do these things. Hybridization of the two varieties of human kick started history. I’m starting to believe the differences we see in measurable IQ scores between Africans and (hybrid) non-Africans.