Date: 03-19-12 21:58
"Although the Neanderthal contribution to the DNA of these individuals is estimated at being just one to four percent of the total, the finding, published in the latest issue of the journal Science, helps to resolve the long-standing controversy over whether or not humans mated with Neanderthals when the two groups encountered each other outside of Africa. "
I'm not sure what is meant by "one to four percent of the total". Of which total? The total human genome? Since both modern human and neanderthal descended from erectus they obviously share many genes. In fact, human genes and chimp genes are 96% to 98% similar. The important thing to prove is that modern human genome contain genes found in the neandethals but not in Africans.
According to the most widely accepted theory, erectus evolved into heidelbergensis in Africa and then migrated out of Africa some 800,000 years ago into Europe. Then neanderthals evolved from heidelbergensi around 300,000 years ago. Modern humans or H. sapiens evolved from heidelbergensis also around 300,000 years ago. So the two will share many heidelbergensis genes. But H. sapiens only left Africa some 70,000 years ago and migrated into Europe around some 45,000 years ago. Therefore, to prove that a common gene is derived from neanderthal there must be proof that it is not found in the African genome prior to 70,000 years ago. Putting it in another way, if a presumptive neanderthal gene is found in African bone prior to 70,000 years ago, then H. sapiens would have gotten it from their African ancestors and not from neanderthals.
But I'm not married to the theory that there is no intermixture between H. sapiens and neanderthals. Show me the proof and I will believe it. But just saying humans and neanderthals share some common genes is not good enough since they obviously share many genes being descended from the same heidelbergensis ancestors.