Fascinating stuff on our not-so-pegigreed origins:
When modern humans migrated out of Africa some 60,000 years ago, they found the Eurasian continent already inhabited by brawny, big-browed Neanderthals. We know that at least some encounters between the two kinds of human produced offspring, because the genomes of people living outside Africa today are composed of some 1 to 4 percent Neanderthal DNA.
Two studies published concurrently in Nature and Science on Wednesday suggest that while the Neanderthal contribution to our genomes was modest, it may have proved vitally important.
Some parts of non-African genomes are totally devoid of Neanderthal DNA, but other regions abound with it, including those containing genes that affect our skin and hair. This hints that the Neanderthal gene versions conferred some benefit, and were kept during evolution.
"It seems quite compelling that as modern humans left Africa, met Neanderthals, and exchanged genes, we picked up adaptive variants in some genes that conferred an advantage in local climatic conditions," says Joshua Akey, who led the study in Science.
I believe "exchanged genes" is science talk for "getting it on."