Re­becca Wragg Sykes

Ar­chae­ol­o­gist based at the Univer­sité de Bordeaux

Focus-Science and Technology - - DISCOVERIES -

“It’s hard to over­state the im­por­tance of find­ing Denny. A decade ago we had no clue that her fa­ther’s peo­ple even ex­isted, much less that chil­dren like her ex­isted. In May 2010 the first Ne­an­derthal genome was pub­lished, prov­ing that rather than usurp­ing them, early Homo

sapi­ens made ba­bies with them. But just the month be­fore, sam­ples from a tiny fin­ger bone in Denisova Cave, Siberia re­vealed an en­tirely new ho­minin species.

“Now known as D3, this bone was at least 10,000 years younger than Denny. Thanks to an­cient DNA, today we’ve iden­ti­fied five Deniso­vans. But we know more about their his­tory as a species than we do about their tech­nol­ogy or even their ap­pear­ance. Some of them had genes for dark hair, skin and eyes, but how tall they were or what their faces were like are mys­ter­ies.

“De­spite all sam­ples so far com­ing from one site, they were far from iso­lated. Both they and Ne­an­derthals bred with H. sapi­ens, but in dif­fer­ent times and places. Asians and na­tive Amer­i­cans have more Ne­an­derthal DNA than Euro­peans, which might re­flect more in­ter­ac­tion in that re­gion, or else­where in a group which later moved east­wards. Denisovan blood is even more un­evenly dis­trib­uted: liv­ing pop­u­la­tions of Ocea­nia and Aus­tralia have up to 25 times more than any­where else. It’s clear we’re see­ing only a frac­tion of the true pic­ture.

“Ne­an­derthals and Deniso­vans weren’t shy of each other, ei­ther. D3’s genes showed in­ter­breed­ing tens of thou­sands of years be­fore she died. Denny’s fa­ther’s fore­bears were also mak­ing ba­bies with Ne­an­derthals up to 17,000 years ear­lier. In­trigu­ingly, those far-off en­coun­ters were with a Ne­an­derthal lin­eage dif­fer­ent from that of Denny’s mother.

“Find­ing the child of a Ne­an­derthal and a Denisovan should make us sit up and think. Un­til now, most ev­i­dence has pointed to small, lo­calised pop­u­la­tions in both species. Added to this, stud­ies map­ping the dis­tances that stone tools were moved from their source pointed to rel­a­tively lim­ited ter­ri­to­ries. On this ba­sis, dom­i­nant the­o­ries em­pha­sised Ne­an­derthals as so­cially ‘ex­clu­sive’: avoid­ing out­siders, lim­ited to to­po­graphic, cul­tural and ge­netic val­leys. If that’s true, it’s un­likely we would ever find the re­sult of such an en­counter, so Denny is telling us some­thing about these mod­els is wrong.

“Pop­u­la­tions were likely small, so the star­tling fact of Denny’s parent­age means the other part of the equa­tion must be wrong: Deniso­vans and Ne­an­derthals must have been quite keen on strangers. But how did pop­u­la­tions who were happy to blend stay so dis­tinct ge­net­i­cally? One the­ory is that mixed chil­dren had a tougher time re­pro­duc­ing, but we just don’t know yet.

“Why does this mat­ter? One of the most in­flu­en­tial ideas about why the Ne­an­derthals dis­ap­peared is that

H. sapi­ens had more ex­ten­sive ter­ri­to­ries – if we map the dis­tances stone tools were car­ried, early H. sapi­ens come out ahead. But find­ing Denny strongly sug­gests stone tool mo­bil­ity can’t be a real mea­sure of so­cia­bil­ity. An­other ex­tinc­tion the­ory may soon bite the dust.”

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