A lit­tle off the top

Re­con­struct­ing a po­lar peo­ple

Pasatiempo - - Pasa Tempos - Paul Wei­de­man

The world of evo­lu­tion­ary bi­ol­o­gists, pa­leo-In­dian ar­chae­ol­o­gists, and DNA re­searchers is all abuzz with re­cent re­search re­ported by Eske Willer­slev of Copen­hagen, Den­mark. With a tuft of hu­man hair har­vested from per­mafrost in Quqer­ta­sus­suk, Green­land, Willer­slev and his team were able to se­cure the first an­cient-hu­man genome. From that they coaxed detailed in­for­ma­tion about a peo­ple who made trans-Arc­tic jour­neys 5,500 years ago and about the man who be­longed to the hair, who hunted in the area four mil­len­nia ago.

Willer­slev is a pro­fes­sor in the bi­ol­ogy depart­ment at the Uni­ver­sity of Copen­hagen and di­rec­tor of the uni­ver­sity’s Cen­tre for GeoGe­net­ics. He talks about his work in a pair of pub­lic events pre­sented by South­west Sem­i­nars: a lec­ture on Sun­day, April 11, and a panel dis­cus­sion on Mon­day, April 12.

The other pan­elists are Bruce Bradley, a pa­leo-In­dian ar­chae­ol­o­gist from the Uni­ver­sity of Ex­eter, United King­dom; Michael B. Collins, pa­leo-In­dian ar­chae­ol­o­gist with the Gault School of Ar­chae­o­log­i­cal Re­search at Texas State Uni­ver­sity-San Mar­cos; and Jane Hill, a his­tor­i­cal lin­guist and re­tired Re­gent’s Pro­fes­sor of An­thro­pol­ogy at the Uni­ver­sity of Ari­zona. The panel mod­er­a­tor is Eric Blin­man, di­rec­tor of the Mu­seum of New Mex­ico’s Of­fice of Ar­chae­o­log­i­cal Stud­ies.

Willer­slev has a fond­ness for ex­plor­ing the cold lands of the north, and the rig­ors of that work have nur­tured in him the nec­es­sary stamina for his in­tensely per­snick­ety re­search pro­to­cols. Such metic­u­lous­ness is es­sen­tial in pre­vent­ing con­tam­i­na­tion of an­cient ar­ti­facts with mod­ern DNA.

In that re­gard, an­cient hair is a safer bet than other DNA sources. “Hair has proven to be very good in the sense that all the con­tam­i­na­tion is on the sur­face only,” Willer­slev said in a re­cent in­ter­view. “Bones are more por­ous, so mi­crobes and other con­tam­i­na­tion can en­ter. Hair is like plas­tic and can be cleaned.”

The path to the cur­rently fa­mous tuft of hair — detailed in a story on the cover of Na­ture mag­a­zine in mid-Fe­bru­ary — was not a straight and easy one. In 2006, Willer­slev shiv­ered through six weeks of search­ing through an­cient hu­man camps in Green­land’s north­ern tun­dra and found noth­ing. Two years later, he found what he was looking for right in Copen­hagen. “The tuft of hair was ba­si­cally found in 1986 dur­ing an ex­ca­va­tion of one of th­ese sites, and peo­ple had for­got­ten about it,” he said. “It was just in a plas­tic bag in the base­ment of the Nat­u­ral His­tory Mu­seum of Den­mark.”

When they re­al­ized they had hair from a pa­leo-Eskimo man, Willer­slev and his team set about ex­am­in­ing and an­a­lyz­ing the hair. The tech­nol­ogy used to read a genome — a com­plete set of chro­mo­somes con­tain­ing all of a species’ ge­netic in­for­ma­tion — is called “sec­ond-gen­er­a­tion high-through­put se­quenc­ing.” The se­quenc­ing de­vice cho­sen by Willer­slev is a ma­chine called the Il­lu­mina.

Af­ter prepa­ra­tion of the genome sam­ple (which in­cluded tag­ging “the mil­lions of frag­ments of ex­tracted DNA with a bar­code-like se­quence to dis­tin­guish them from stray mod­ern hu­man DNA,” ac­cord­ing to the story in Na­ture), it was sent to the Bei­jing Ge­nomics In­sti­tute. “They have 120 of th­ese ma­chines in China,” Willer­slev said. “It would have taken us a year to do it with the two Il­lu­mina ma­chines we have in Copen­hagen, but it took two-and-one-half months us­ing 36 ma­chines to­gether in China. We wanted to fin­ish this very quickly, be­cause we were in com­pe­ti­tion with an­other group.”

The project yielded two ground­break­ing re­sults. “One is that you can use the genome to de­scribe the in­di­vid­ual, the phys­i­cal, and phe­no­typ­i­cal char­ac­ter­is­tics,” Willer­slev said. “We can say this guy had brown eyes, darker skin, shovel-form front teeth, and a ten­dency to bald­ness, and that he was ge­net­i­cally adapted to cold tem­per­a­tures. We can also see that this in­di­vid­ual was quite in­bred, sim­i­lar to cousin mar­riages, which sug­gests that th­ese guys were liv­ing in small fam­ily groups that were iso­lated from one an­other.

“Even though he was found in Green­land in the New World, his con­tem­po­rary rel­a­tives ac­tu­ally live in north­east­ern Siberia. So it strongly sug­gests there was mi­gra­tion from the Old World to the New World about 5,500 years ago that didn’t leave any con­tem­po­rary de­scen­dants in the New World — so mi­gra­tion in­de­pen­dent of Na­tive Amer­i­can an­ces­tors and in­de­pen­dent of Inuit an­ces­tors.”

This flies in the face of a pre­vi­ous the­ory — that the ear­li­est set­tlers in Green­land were Na­tive Amer­i­can or Inuit. The Willer­slev team com­pared the pa­leo-In­dian DNA with that of mod­ern hu­mans and

Cold bear­ings: Eske Willer­slev Op­po­site page: artist’s im­pres­sion of a pa­leo-Eskimo man by Nuka God­fred­sen; im­ages cour­tesy Na­ture mag­a­zine

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