Ear­li­est Amer­i­cans came from Asia in a rush, an­cient DNA shows

The Beaufort Gazette (Sunday) - - News - BY CARL ZIM­MER

Nearly 11,000 years ago, a man died in what is now Ne­vada. Wrapped in a rab­bit-skin blan­ket and reed mats, he was buried in a place called Spirit Cave.

Now sci­en­tists have re­cov­ered and an­a­lyzed his DNA, along with that of 70 other an­cient peo­ple whose re­mains were dis­cov­ered through­out the Amer­i­cas. The find­ings lend as­ton­ish­ing de­tail to a story once lost to pre­his­tory: how and when hu­mans spread across the Western Hemi­sphere.

The ear­li­est known ar­rivals from Asia were al­ready split­ting into rec­og­niz­ably dis­tinct groups, the re­search sug­gests. Some of th­ese pop­u­la­tions thrived, be­com­ing the an­ces­tors of in­dige­nous peo­ples through­out the hemi­sphere.

But other groups died out en­tirely, leav­ing no trace save for what can be dis­cerned in an­cient DNA. In­deed, the new ge­netic re­search hints at many dra­matic chap­ters in the peo­pling of the Amer­i­cas that ar­chae­ol­ogy has yet to un­cover.

“Now, this is the grist for ar­chae­ol­o­gists,” said Ben Pot­ter of the Univer­sity of Alaska, who was not in­volved in the new pa­pers. “Holy cow, this is awe­some.”

Ear­lier stud­ies had in­di­cated that peo­ple moved into the Amer­i­cas at the end of the last ice age, trav­el­ing from Siberia to Alaska across a land bridge now un­der the Ber­ing Sea. They spread south­ward, even­tu­ally reach­ing the tip of South Amer­ica.

Un­til re­cently, ge­neti­cists could of­fer lit­tle in­sight into th­ese vast mi­gra­tions. Five years ago, just one an­cient hu­man genome had been re­cov­ered in the Western Hemi­sphere: that of a 4,000-year-old man dis­cov­ered in Green­land.

The lat­est batch of analy­ses, pub­lished in three sep­a­rate stud­ies this week, marks a turn­around. In the past few years, re­searchers have re­cov­ered the genomes of 229 an­cient peo­ple from teeth and bones dis­cov­ered through­out the Amer­i­cas.

One of them is a rare in­di­vid­ual, only the sec­ond so-called An­cient Beringian whose DNA has ever been an­a­lyzed.

The first, de­scribed in Jan­uary by Eske Willer­slev, a ge­neti­cist at the Univer­sity of Copen­hagen, was a 11,500-year-old girl whose re­mains were found in eastern Alaska.

The sec­ond was dis­cov­ered hun­dreds of miles away, in western Alaska, and lived 9,000 years ago, Willer­slev and his col­leagues re­ported Thurs­day in the jour­nal Sci­ence.

The An­cient Beringians separated from the an­ces­tors of liv­ing in­dige­nous peo­ple in the Amer­i­cas about 20,000 years ago. The new find­ings sug­gest they en­dured for sev­eral thou­sand years. Then they dis­ap­peared, leav­ing no known ge­netic trace in liv­ing peo­ple.

But an­other wave of mi­grants from Siberia did not stop in Alaska. They kept mov­ing, even­tu­ally ar­riv­ing south of the ice age glaciers. Then they split into two branches.

One group turned and headed north, fol­low­ing the re­treat­ing glaciers into Canada and back to Alaska. The other branch took a remarkable jour­ney south.

The ge­netic data sug­gest that this group spread swiftly across much of North Amer­ica and South Amer­ica about 14,000 years ago. The ex­pan­sion may have taken only cen­turies.


A photo pro­vided by André Strauss shows the ex­ca­va­tion of a skele­ton ap­prox­i­mately 9,600 years old in a rock shel­ter in Brazil. New DNA analy­ses show the ear­li­est known Amer­i­cans split into dis­tinct groups af­ter they crossed a land bridge from Asia.

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