Neanderthals had outsize effect on human biology

Aug 3, 2015

Photograph by Xin Lu/Getty

By Ewen Callaway

Our ancestors were not a picky bunch. Overwhelming genetic evidence shows that Homo sapiens had sex with Neander­thals, Denisovans and other archaic relatives. Now researchers are using large genomics studies to unravel the decidedly mixed contributions that these ancient romps made to human biology — from the ability of H. sapiens to cope with environments outside Africa, to the tendency of modern humans to get asthma, skin diseases and maybe even depression.

The proportion of the human genome that comes from archaic relatives is small. The genomes of most Europeans and Asians are 2–4% Neanderthal1, with Denisovan DNA making up about 5% of the genomes of Mela­nesians2 and Aboriginal Australians3. DNA slivers from other distant relatives probably pepper a variety of human genomes4.

But these sequences may have had an outsize effect on human biology. In some cases, they are very different from the corresponding H. sapiens DNA, notes population geneticist David Reich of Harvard Medical School in Boston, Massachusetts — which makes it more likely that they could introduce useful traits. “Even though it’s only a couple or a few per cent of ancestry, that ancestry was sufficiently distant that it punched above its weight,” he says.

Last year, Reich co-led one of two teams that catalogued the Neanderthal DNA living on in modern-day humans5, 6. The studies hinted that Neanderthal versions of some genes may have helped Eurasians to reduce heat loss or grow thicker hair. But the evidence that these genes were beneficial was fairly weak.

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2 comments on “Neanderthals had outsize effect on human biology

  • Neanderthals had outsize effect on human biology The article says nothing to support the claim in the title.
    If anything the research findings in the article stress how small, “tiny” or ambiguous the Neanderthal DNA effects have on human biology.

    The genomes of most Europeans and Asians are 2–4% Neanderthal1 That’s a huge range within a small range that still marginalizes Europeans and Asians with less than 1% Neanderthal DNA. Presumably hundreds of millions of Africans have no Neanderthal DNA (0%). Before scientists can draw conclusions of “outsize effect,” they admit that far more research, and far more detailed research is needed.

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  • Small genetic differences can make huge bodily changes.

    While the genetic difference between individual humans today is minuscule – about 0.1%, on average – study of the same aspects of the chimpanzee genome indicates a difference of about 1.2%. The bonobo (Pan paniscus), which is the close cousin of chimpanzees (Pan troglodytes), differs from humans to the same degree. The DNA difference with gorillas, another of the African apes, is about 1.6%. Most importantly, chimpanzees, bonobos, and humans all show this same amount of difference from gorillas. A difference of 3.1% distinguishes us and the African apes from the Asian great ape, the orangutan. How do the monkeys stack up? All of the great apes and humans differ from rhesus monkeys, for example, by about 7% in their DNA.

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