Who We Are and How We Got Here: An­cient DNA and the New Sci­ence of the Hu­man Past

The Week (US) - - 24 - By David Re­ich

(Pan­theon, $29) The first draft of the true his­tory of hu­man­ity has just been writ­ten and “it is thrilling in its clar­ity and scope,” said Peter Forbes in The­Guardian.com. Ge­neti­cist David Re­ich is a leader in the study of an­cient DNA, and his new book syn­the­sizes the find­ings with which he and oth­ers in the field have been up­end­ing prior con­ven­tional wis­dom. Re­ich’s lab at Har­vard Med­i­cal School was the source of the 2010 find­ing that all non-Africans have Ne­an­derthal DNA in their genome, the first in a flurry of find­ings in­di­cat­ing that hu­mans of about 50,000 years ago shared the planet and in­ter­bred with var­i­ous other ho­minins. Fur­ther, our an­ces­tors did not sim­ply mi­grate out of Africa in a tri­umphant, ev­er­ex­pand­ing tide. In­stead, pop­u­la­tions shifted one way, then the other, eras­ing al­most ev­ery mod­ern claim, out­side of Africa, of a tie to a ter­ri­tory’s orig­i­nal set­tlers. “Re­al­ity, it turns out, is more com­plex and in­ter­est­ing than sci­en­tists ever imag­ined,” said Razib Khan in Na­tion­alRe­view.com. Af­ter ex­plain­ing how ge­neti­cists learned in just the past decade to isolate and de­code DNA in an­cient hu­man or ho­minin re­mains, Re­ich dis­cusses what this new Rosetta stone has re­vealed. Con­sider Europe, which at the end of the last ice age was dom­i­nated by dark-skinned, blue-eyed hunter-gath­er­ers who were then dis­placed about 10,000 years ago by mi­grant farm­ers from the Mid­dle East, who also spread south into the Asian sub­con­ti­nent. Some 5,000 years later, an­other wave ar­rived from the Rus­sian steppe, link­ing Euro­peans ge­net­i­cally to Na­tive Amer­i­cans. In short, “we should stop ob­sess­ing with our in­di­vid­ual an­ces­tries,” said Bryan Ap­p­le­yard in The Sunday Times (U.K.) “All hu­mans are a hope­less ge­netic stew.”

But Re­ich does speak about race, and in a way that in­di­cates his grasp of the con­cept is “se­ri­ously flawed,” said 67 schol­ars who signed an open let­ter pub­lished by Buz­zFeed.com. Though Re­ich de­clares race a so­cial con­struct, he in­sists on the need to rec­og­nize “non­triv­ial” dif­fer­ences in the ge­netic makeup of pop­u­la­tions that hap­pen to have been la­beled as races. We don’t deny his point that ge­o­graph­i­cally based ge­netic vari­a­tion ex­ists, or that some pop­u­la­tions carry ge­netic vari­a­tions that, for ex­am­ple, make mem­bers more prone to con­tract­ing a par­tic­u­lar ail­ment. But “race” is not the right word for such groups even as short­hand. Lis­ten more closely to Re­ich, then, be­cause he would agree, said Turi King in Na­ture. He’s say­ing we need a less fraught way of talk­ing about group dif­fer­ences, and his book “goes some way to start­ing that con­ver­sa­tion.”

For­ever fam­ily: A model Ne­an­derthal

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