Though other explanations are possible, one of the simplest scenarios is that early modern humans interbred with Neandertals in the Middle East, after leaving Africa and before spreading into Eurasia.
Approximately 1 to 4 percent of the modern human genome seems to be from Neandertals, the authors estimate. Population models have suggested that when a colonizing population comes across a resident population, even a small amount of interbreeding can be widely reflected in the colonizing populations' genome, if that population then expands significantly. Thus, the relatively low percentage of Neandertal DNA in the modern human genome may suggest that interbreeding was actually fairly limited.
The comparisons between the Neandertal and modern humans also produced many other results that may ultimately be more important than the admixture discovery when it comes to giving us a better understanding of ourselves.
"It's cool to think that some of us have a little Neandertal DNA in us, but, for me, the opportunity to search for evidence of positive selection that happened shortly after the two species separated is probably the most fascinating aspect of this project," Pbo said.
His team devised a method to look for regions of the modern-human genome where new genes have spread through the population since the two species diverged. These genes are likely to have somehow improved early humans' odds for survival or reproduction.
The researchers screened the genomes of five modern-day humans from around the world to look for genomic
|Contact: Natasha Pinol|
American Association for the Advancement of Science