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MSNBC: Could our big brains come from Neanderthal?
$this->bbcode_second_pass_quote('', 'W')ASHINGTON - Neanderthals may have given the modern humans who replaced them a priceless gift — a gene that helped them develop superior brains, U.S. researchers reported on Tuesday.
And the only way they could have provided that gift would have been by interbreeding, the team at the Howard Hughes Medical Institute and the University of Chicago said.
Their study, published in the Proceedings of the National Academy of Sciences, provides indirect evidence that modern Homo sapiens and so-called Neanderthals interbred at some point when they lived side by side in Europe.
"The gene microcephalin (MCPH1) regulates brain size during development and has experienced positive selection in the lineage leading to Homo sapiens," the researchers wrote.
Positive selection means the gene conferred some sort of advantage, so that people who had it were more likely to have descendants than people who did not. Lahn's team estimated that 70 percent of all living humans have this type D variant of the gene.
"By no means do these findings constitute definitive proof that a Neanderthal was the source of the original copy of the D allele. However, our evidence shows that it is one of the best candidates," Lahn said.
The researchers reached their conclusions by doing a statistical analysis of the DNA sequence of microcephalin, which is known to play a role in regulating brain size in humans. Mutations in the human gene cause development of a much smaller brain, a condition called microcephaly.
They noted that
this D allele is very common in Europe, where Neanderthals lived, and
more rare in Africa, where they did not. Lahn said it is not yet clear what advantage the D allele gives the human brain.
"The D alleles may not even change brain size; they may only make the brain a bit more efficient if it indeed affects brain function," Lahn said.
Now his team is looking for evidence of Neanderthal origin for other human genes.