Meet your in­ner cave­man

Relics of ne­an­derthal dna iso­lated in hu­man genome.

The Star Malaysia - Star2 - - SCIENCE - By SETH BORENSTEIN

NEXT time you call some­one a Ne­an­derthal, bet­ter look in a mir­ror. Many of the genes that help de­ter­mine most peo­ple’s skin and hair are more Ne­an­derthal than not, ac­cord­ing to two new stud­ies that look at the DNA fos­sils hid­den in the mod­ern hu­man genome.

About 50,000 years ago, mod­ern-day hu­mans mi­grated out of Africa, north to Europe and East Asia, and met up with fur­row­browed Ne­an­derthals that had been in the colder cli­mates for more than 100,000 years. Some of the two species mated. And then the Ne­an­derthals died off as a species – ex­cept for what’s left in­side of us.

Sci­en­tists iso­lated the parts of the mod­ern hu­man ge­netic blue­print that still con­tain Ne­an­derthal rem­nants. Over­all, it’s barely more than 1%, said two stud­ies re­leased last week in the jour­nals Na­ture and Sci­ence.

How­ever, in some places, such as the DNA re­lated to the skin, the ge­netic in­struc­tions are as much as 70% Ne­an­derthal and in other places there’s vir­tu­ally noth­ing from the species that’s of­ten por­trayed as brutish cave­men.

The dif­fer­ence be­tween where Ne­an­derthal DNA is plen­ti­ful and where it’s ab­sent may help sci­en­tists un­der­stand what in our genome “makes hu­mans hu­man”, said Univer­sity of Wash­ing­ton genome sci­en­tist Joshua Akey, lead au­thor of the pa­per in Sci­ence.

The stud­ies mostly ex­am­ined the genomes of peo­ple whose an­ces­tors left Africa at some point. Peo­ple whose an­ces­tors have all stayed in Africa have al­most no Ne­an­derthal DNA be­cause there was lit­tle in­ter­breed­ing.

Har­vard Univer­sity re­searcher Sri­ram Sankarara­man, the lead au­thor of the Na­ture study, said the place where Ne­an­derthal DNA seemed to have the most in­flu­ence in the mod­ern hu­man genome has to do with skin and hair. Akey said those in­struc­tions are as much as 70% Ne­an­derthal.

“We’re more Ne­an­derthal than not in those genes,” Akey said.

Sankarara­man cau­tions that sci­en­tists don’t yet know just what the Ne­an­derthal DNA dic­tates in our skin and hair.

Sarah Tishkoff, a pro­fes­sor of ge­net­ics and biology at the Univer­sity of Penn­syl­va­nia who was not part of ei­ther study, the­o­rised that the Ne­an­derthal DNA prob­a­bly helped the darker hu­mans out of Africa cope with the cooler, less bright north. Liv­ing in cooler Europe means less ul­tra­vi­o­let light and less vitamin D from the Sun.

Darker skin blocks more of those needed rays, so lighter skin is more ad­van­ta­geous in the north and it seems that hu­mans adopted that Ne­an­derthal adap­ta­tion, she said.

Another area where we have more Ne­an­derthal DNA is parts of ge­netic codes that have to do with cer­tain im­mune sys­tem func­tions, Sankarara­man said. Again, sci­en­tists can’t say more than that th­ese Ne­an­derthal genes seem con­nected to cer­tain dis­eases, such as type 2 di­a­betes and Crohn’s disease and lu­pus, but they are there.

Tiskhoff and Akey said one of the most in­ter­est­ing parts in com­par­ing hu­man and Ne­an­derthal genomes is where we don’t see any cave­man in­flu­ence. That, Tiskhoff said, is “what makes us uniquely hu­man” and those re­gions of ge­netic code “you just can’t mess with”.

One of those ar­eas has been heav­ily con­nected to genes that de­ter­mine speech and com­mu­ni­ca­tion and there’s noth­ing Ne­an­derthal there, Akey said. This fits with the­o­ries that lack of com­mu­ni­ca­tion skills hurt Ne­an­derthal man and that speech abil­ity was a dis­tinctly hu­man ad­van­tage, he said.

And the study in Na­ture found some­thing that may help ex­plain why the brutish and vir­ile cave­men haven’t in­flu­enced hu­mans much: they may have made ba­bies, but the male hy­brids of Ne­an­derthals and hu­mans weren’t very fer­tile. Sci­en­tists fig­ured that out be­cause the genes as­so­ci­ated with the tes­ti­cles in hu­mans and the X chro­mo­some were un­usu­ally empty of Ne­an­derthal in­flu­ence.

While Ne­an­derthal males them­selves were likely good at breed­ing, their half-hu­man sons weren’t and “they must have been dis­ap­pointed in their sons”, said Na­ture co-au­thor Svante Paabo of the Max Planck In­sti­tute in Ger­many. The Na­ture pa­per found that peo­ple of more East Asian de­scent had slightly more Ne­an­derthal than Euro­peans, in­di­cat­ing that there may have been a sec­ond wave of in­ter­breed­ing in Asia, re­searchers said.

The Na­ture study found Bei­jing res­i­dents with Han Chi­nese an­ces­tors had the high­est Ne­an­derthal DNA rate: 1.4%. Los An­ge­les res­i­dents of Mex­i­can de­scent had 1.22% Ne­an­derthal DNA. In Europe, Finns had the high­est Ne­an­derthal DNA rate with 1.2%. Utah res­i­dents with north­ern and western Euro­pean roots came in at 1.17%. And Puerto Ri­cans had only 1.05%. All th­ese peo­ple still can trace their ge­netic roots to early hu­mans in Africa than to Ne­an­derthals in an­cient Europe.

Three out­side sci­en­tists praised the two stud­ies, which used dif­fer­ent tech­niques to reach sim­i­lar con­clu­sions. And those con­clu­sions were so close to each other and stan­dard evo­lu­tion the­ory that it all fits to­gether in a scary way for sci­en­tists used to find­ings that sur­prise, said New York Univer­sity an­thro­pol­ogy pro­fes­sor Todd Disotell.

Disotell re­cently had his genome tested by a pri­vate com­pany and found he’s got more Ne­an­derthal DNA than most peo­ple, about 2.9%: “I’m quite proud of that.” — AP

Boul­der dash: a replica of a ne­an­derthal man at a mu­seum in Mettmann, Ger­many. next time you call some­one a ne­an­derthal, bet­ter look in a mir­ror. Much of the genes that help de­ter­mine most peo­ple’s skin and hair are more ne­an­derthal than not, ac­cord­ing to two new stud­ies. — aP

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