It has been proven that non-African populations average 2.5% Neanderthal DNA. There is a $300 test that I am going to take to find out how much I have, but I suspect it's more than 2.5 percent. Now what's interesting about this is that some people think we picked up all kinds of good things from the Neanderthals. Essentially primitive people did nothing until about 35,000 year ago, then suddenly whites exploded all over the place and created all sorts of advances. Some think it would have never happened without the introduction of Neanderthal DNA.
Then on the other hand we have Africans, who have no Neanderthal DNA, and are stuck in 20,000 BC. I suspect the same would have happened to whites and Asians without interbreeding with Neanderthals.