Tomorrow’s Science will have a series of freely available papers on the Neanderthal genome. One claim is that that between 1% and 4% of the DNA of certain modern groups is attributable to hybridization between Homo sapiens and Neanderthals. Carl Zimmer and John Hawks have more. Jerry Coyne has a handy-dandy guide to the paper here.
The original paper is here and the abstract reads:
Neandertals, the closest evolutionary relatives of present-day humans, lived in large parts of Europe and western Asia before disappearing 30,000 years ago. We present a draft sequence of the Neandertal genome composed of more than 4 billion nucleotides from three individuals. Comparisons of the Neandertal genome to the genomes of five present-day humans from different parts of the world identify a number of genomic regions that may have been affected by positive selection in ancestral modern humans, including genes involved in metabolism and in cognitive and skeletal development. We show that Neandertals shared more genetic variants with present-day humans in Eurasia than with present-day humans in sub-Saharan Africa, suggesting that gene flow from Neandertals into the ancestors of non-Africans occurred before the divergence of Eurasian groups from each other.