May 2, 2010

Possible new extinct human species identified

March 25, 2010
Courtesy Nature Publishing Group
and World Science staff

A pre­vi­ously un­known line­age of hu­mans has been iden­ti­fied based on genes ex­tracted from a bit of bone found in Si­be­ria, sci­en­tists say.

The find­ing may rep­re­sent a new spe­cies that lived along­side Ne­an­der­thal peo­ple and an­a­tom­ic­ally “mod­ern” hu­mans in that re­gion, ac­cord­ing to the re­search­ers.

Denisova cave from the out­side. (Cred­it: Bence Vio­la)

“I at first did­n’t be­lieve” that the re­sult could be pos­si­ble, said one of the re­search­ers in­volved with the find­ing, Svante Pääbo of the Max Planck In­sti­tute for Ev­o­lu­tion­ary An­thro­po­l­ogy, Leip­zig, Ger­ma­ny. How­ev­er, Pääbo said, ge­net­ic test re­sults showed “it’s some new crea­ture that has not been on our ra­dar screen so far.” The find­ings are pub­lished in the March 25 is­sue of the re­search jour­nal Na­ture.

The con­clus­ions were based on the se­quenc­ing, or de­cod­ing, of the or­gan­is­m’s “mi­to­chon­drial ge­nome,” that is, DNA from a cel­lu­lar struc­tures called the mi­to­chon­dria. 

Mi­to­chon­chon­drial DNA is not in­her­it­ed the same way as the rest of an an­i­mal’s DNA, but rath­er is passed down only from the moth­er. Be­cause un­like oth­er DNA it re­mains re­la­tive­ly un­changed when passed down through genera­t­ions, it plays an im­por­tant role in an­ces­try stud­ies, in par­tic­u­lar in de­ter­min­ing an or­gan­is­m’s moth­er-line an­ces­try.

The ge­net­ic se­quenc­ing point­ed to a pre­vi­ously un­known ho­minin, or ex­tinct mem­ber of the hu­man line­age, who lived in the Al­tai moun­tains of south­ern Si­be­ria be­tween 48,000 and 30,000 years ago, said the re­search­ers.

The inves­tigat­ing team, which in­clud­ed al­so re­search­ers from the Un­ited States, Aus­tria and Rus­sia, se­quenced genes from a ti­ny piece of pinky fin­ger bone found in Denisova cave in the Al­tai Moun­tains. They com­pared the mi­to­chon­drial ge­nome with that of mod­ern hu­mans and Ne­an­der­thals. 

The anal­y­sis in­di­cat­ed that the crea­ture shared a com­mon fe­male or “mi­to­chon­drial” an­ces­tor with mod­ern hu­man and Ne­an­der­thals about a mil­lion years ago, the sci­en­tists said. That’s about twice as old as what is be­lieved to be the most re­cent com­mon mi­to­chon­drial an­ces­tor of mod­ern hu­mans and Ne­an­der­thals. Ne­an­der­thals were a stocky, now ex­tinct sub­group of our spe­cies, Ho­mo sapi­ens, who lived in Eu­rope and parts of Asia from around 100,000 to 30,000 years ago.

The age of the fos­sil and the lay­ers of earth in which they turned up al­so sug­gest “the Deni­sova ho­minin lived close in time and space with Ne­an­der­thals as well as with mod­ern hu­mans,” the re­search­ers wrote.

Al­though re­search­ers said they lacked de­fin­i­tive enough in­forma­t­ion to de­clare the fos­sil a new spe­cies, they said it al­so likely rep­re­sented a sep­a­rate migra­t­ion out of Af­ri­ca from mod­ern hu­mans and Ne­an­der­thals, both of whom are thought to have orig­i­nat­ed in that con­ti­nent. The in­ves­ti­ga­tors al­so said they have no in­forma­t­ion yet that could serve to phys­ic­ally de­scribe any un­usu­al char­ac­ter­is­tics that the new­found hu­man rela­tive might have pos­sessed.



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