Interbreeding With Other Human Species Helped Our Ancestors Spread Worldwide

By Joseph Castro | June 20, 2011 4:24 pm

Could Neanderthal DNA have protected our ancestors from diseases?

What’s the News: While we humans have certainly outlasted our hominin cousins, new research shows that Neanderthal and Denisovan genes may have helped us spread far and wide. By mating with the two species, our ancestors acquired genes that allowed them to adapt to diseases outside of Africa far quicker than would have been otherwise possible, according to Peter Parham, a professor of microbiology and immunology at Stanford University.

How the Heck:

  • Parham began by taking a close look at a family of genes called human leukocyte antigens (HLAs), which play a central role in our body’s immune responses. We are able to react to a wide array of diseases because our HLA genes are highly variable, each containing dozens of alleles (forms of genes).
  • Our ancestors in Africa, however, would have had a small number of HLA alleles because they likely traveled in small bands and had little contact with other groups. Moreover, their HLAs would have only protected them against African diseases.
  • When Parham compared the HLAs of modern humans with those of Neanderthals and Denisovans, he noticed some overlaps. In particular, he found that HLA-C*0702, an allele common in Europeans and Asians but nonexistent in Africans, was also present in the Neanderthal genome. Similarly, HLA-A*11, which is found in modern Asians but not in Africans, popped up in Denisovan DNA.
  • Overall, about 50 percent of HLA Class I alleles in Europeans seemed to come from Neanderthals, 70 to 80 percent in East Asians from Denisovans, and 90 to 95 percent in Papuans from Denisovans, Parham said at a recent Royal Society meeting.

What’s the Context:

Not So Fast: It is unclear what the research means for the various models of human evolution, and some questions still linger. Does the overlapping of HLA alleles reflect a single massive migration out of Africa, where humans ran into Neanderthals and Denisovans all at once, or is it somehow a product of multiple migrations? And how essential was the interbreeding for our ancestors’ survival?

(via New Scientist)

Image: Wikimedia Commons / Ökologix

CATEGORIZED UNDER: Human Origins
  • fintin

    This really makes me wonder who our true ancestors were…..

  • http://discovermagazine.com Iain

    Think about it, no tv, no radio, no books, no puppeteers, no animee, no internet, our ancestors didn’t have much for entertainment except the most special fun thing ever. Ya they bred with rock piles too, thinking that there was maybe a snake in it.

  • dave chamberlin

    If this is true than their was significant genetic advantage for both Denisovans and Neanderthals over fresh out of Africa modern humans in combating infectious diseases just like Europeans had a significant advantage over Amerinds after they arrived in the Americas. It explains why modern humans were long delayed from expanding beyond the middle east, we needed their genetic protection from the diseases they carried, so a human hybrid was created by interbreeding. We know that their was a bottleneck in the very early human population that spread though out the world, excluding sub saharan Africa, and this provides a scenario as to why. Once their was a sustainable population that combined genetic protection from disease as well as near modern intelligence these hybrid humans spread very rapidly and the rest, as they say is history. I paint too simple a picture because we know we interbred with two different groups in two different times and places. Also there is debate among highly respected experts in this field such as John Hawks if these findings are correct. Razib Kahn over at the Discover blog Gene Expressions has a post up titled Massive Denisovan and Neanderthal Introgression that explains the particulars far better than I can. East Asians were believed to have near to zero percent Denisovan lineage, but here they are reported to have 70 to 80 % Denisovan HLA. If true it signifies a significant advantage provided by Denisovan HLA, at least in Asia.

  • Rick

    The reading of the comments was exhausting. I suspect Al Cahol was a contributing
    Author. Found the comments nearly worthless, unlike the discussions found on Channel3000.com. I love Discover Magazine & have subscribed for years. I will stick to the articles and skim the responses.

  • dave chamberlin

    there are no discussions on channel3000, I suspect Rick ain’t real

  • Elvis Othello

    Not only was there no discussion on Channel3000, but, well, at first I thought it was a parody, as apparently is Rick–who cannot read grouped sentences for meaning. Yikes.

  • Laura

    The New Guinea link doesn’t work.

  • Avanti Shrikumar

    Aren’t species defined as being incapable of interbreeding?

  • Joseph Castro

    Link fixed.

  • http://www.biblethug.com Bibleguy

    The Bible is clear on the matter. God created Adam 6000 years ago. So this story is obviously wrong

  • dave chamberlin

    I wonder if Bibleguy really thinks all those scientists out there are all in cahoots together. Maybe he thinks they all get together in secret satanic graduate school get togethers so that they can all keep their story straight. Think of all those scientific journals and how hard they must work to keep all those lies about fossils so perfectly in line with each other. That dirty devil must have a lot of editors and writers working for him, constantly adding more non conflicting detail to his obviously wrong plot to undermine the one true book.

  • Sean

    If bibleguy believes so strongly why is he reading science articles at all?

  • zachary

    Come on guys, don’t feed the troll.

  • dave chamberlin

    @13 I respect your opinion on not feeding the trolls, but to me trolls are attention seekers saying something shocking to get attention. My guess is bibleguy is genuine, doesn’t only half the USA believe in evolution? When someone starts talking about Atlantis, or is purposely rude or stupid I agree with you, to give them any kind of attention means they win.

  • Julia

    With regard to the Bible, Genesis 6:1-4 talks about the sons of God and the daughters of man, and also nephilim (sometimes translated “giants”), which is a 3rd thing. This implies at least 3 different human-like species, directly referenced in the Bible, that the Bible says interbred. This is completely in line with the premise of this article.

  • Patrick Buck

    Question: would you have sex with a Neandertal, in circumstances where doing so would not contradict your personal moral code? I would, if I liked the Neandertal and found him/her attractive.

  • wblogan

    So, if Neanderthals wore genes,
    what’s the deal with Levi-Strauss?
    Another “alien” explanation, or
    twisted logic conspiracy theory?
    Is it just me, or does it smell all
    cave man up in here?

  • http://www.facebook.com/pabloandrade.dasilva Pablo Andrade da Silva

    genesis was writen by Moses and most certainly unable to write things down in a modern scientifical way,but i am a cristian and it doesn,t keep me from loving science – just shows me how perfect things are.

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