In regards to the comments concerning how human/Neandertal contact may have affect each species, this article which appeared in Science Magazine: The Shaping of Modern Human Immune Systems by Multiregional Admixture with Archaic Humans, Vol 334 7 October 2011, suggests that humans benefitted greatly. Apparently, we picked up alleles that strengthened our immune system. http://www.sciencemag.org/content/334/6052/89.abstract?sid=63979397-4ff4-4778-b1be-3c595c0506f1