Cosmos - - Special Feature -

Hu­mans also in­ter­bred with the Deniso­vans, a group known only from a pinky finger bone and a few teeth re­cov­ered from a Siberian cave, dat­ing to about 100,000 years ago. (Ne­an­derthal and Homo sapien re­mains have also been found in the cave.) Most of what we know of the Deniso­vans comes from the an­cient DNA gleaned from these re­mains. Mod­ern Abo­rig­i­nal Aus­tralians and Me­lane­sians have the high­est per­cent­age of Deniso­van DNA in their genome (2-4%), while mod­ern Ti­betans are likely to have in­her­ited their abil­ity to cope with high alti­tudes from Deniso­van an­ces­tors.

All this sug­gests that Deniso­vans could have lived through­out Asia. In­deed, 10,000 to 14,000 year-old fos­sils from caves in south­west China – the Red Deer Cave and Longlin peo­ple – may even turn out to be Deniso­van.

These stone-age cave dwellers are be­lieved to have borne traits sim­i­lar to mod­ern hu­mans, as well as more ar­chaic fea­tures. “We don’t quite know fully what we’re deal­ing with,” says Dar­ren Curnoe, from the Univer­sity of New South Wales. A small fe­mur from Longlin, for in­stance, is more rem­i­nis­cent of Homo erec­tus than mod­ern Homo sapi­ens, he says, and could hint at Homo erec­tus hav­ing sur­vived and spawned de­scen­dants in Asia much later than once thought.

The Deniso­vans weren’t a picky lot. In ad­di­tion to mat­ing with hu­mans, their DNA also bears the hall­marks of in­ter­breed­ing with Ne­an­derthals and a more ar­chaic mys­tery species. Some spec­u­late that this could be Homo erec­tus, or

Homo flo­re­sien­sis, but un­til ef­forts to ex­tract DNA from these species is suc­cess­ful we won’t know for sure.

‘I’D HAVE LOVED to have been on the planet 60,000 years ago,” says ar­chae­o­log­i­cal sci­en­tist Richard “Bert” Roberts, from the Univer­sity of Wol­lon­gong, who helped date the Hob­bit re­mains. “We used to have a fabulous time, with all sorts of other hu­mans run­ning around the planet.”

How­ever many times we and our ex­tinct rel­a­tives did in­ter­breed, these an­cient DNA stud­ies high­light how dif­fer­ent mod­ern times are to al­most any other pe­riod in our pre-his­tory. We roam the world now as the sin­gle liv­ing rep­re­sen­ta­tive of the Homo line, all pre­vi­ous times have seen the world pop­u­lated by mul­ti­ple re­lated – and of­ten in­ter­min­gling – species. Our once bushy fam­ily tree has been pruned back to a lone twig.

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