14 December 2011

Denisovan genes as markers of migration

There's too much to cover here in a short post, but I'll sketch what I understand as the basics.  Denisovans were ?pre-humans/proto-humans of the genus Homo who died out as a species.  They were genetically distinct from us, but some of their genes are present in modern humans.  The distribution of those genes today is not random, as shown by the figure above.
“We haven’t been a very exclusive species, with a very narrow origin,” said Martin Jacobsson. Interbreeding with other members of the human family tree “is not a unique event. It’s a more complex story than we thought before.”

In a study published Oct. 31 in the Proceedings of the National Academy of Sciences, Jacobsson and co-author Pontus Skoglund searched through 1,500 human genome scans from around the world for genes found in Denisovans but not chimpanzees or Neanderthals.

While the previous finding of Denisovan inheritance involved analysis of ultra-high-resolution human genome scans, of which only a few exist, Jacobsson used low-resolution scans. These are more commonly available and allowed the researchers to detect Denisovan signals in genomes from mainland southeast Asia. A signal also appeared in South America, but Jacobsson said that’s probably a false positive.
I'm interested in the South American hits because of my belief in early colonization of the Americas from Oceania.  I believe there's good evidence that the chickens in Chile and Peru came from Polynesia in pre-Columbian times.

Further information at Ars Technica, via Right-reading.


  1. Ibera, the British Isles and a large lump of Africa seem to have wandered away!

  2. I agree with you on the Polynesian origins of South American chickens.

  3. How would this be evidence of "colonization" rather than simple contact or trade?

  4. Steve, I was using "colonization" in the sense of "first arrival," meaning that no humans were there before them.

    Current standard hypothesis is that early man arrived in the Americas via Beringia, then moved southward. I (and some others) think that early man was capable of transoceanic travel and could have gone from Asia (or Africa) to South America without colonizing North America first.

  5. The migration went the other way, too, since the yam and sweet potato are native to South America but endemic in Polynesia.

  6. If the Denisovans (and Neanderthals) were a different species, then I guess this is evidence in our genome of widespread historical bestiality.

  7. Ok, thanks Minnesotastan I misunderstood what you meant.

  8. Have you seen Buckminster Fuller's Polynesian migration theories? He'd be quite interested to see this, I think. For a quick overview see his "Tetrascroll".

  9. Check out the history of king Juba
    from north west Africa.
    He had no forests but a huge navy.
    Send a boatload or two of shipwrights and sailors over to south america or the mississippi and then you have a boatyard that your neighbours don't know about.


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