In May 2010 paleogeneticist Svante Pääbo and colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig published a draft genome sequence of DNA obtained from Neanderthal bones recovered from Vindija Cave that were around 38,000 years old. Neanderthal fossils found in this cave near the city of Varaždin, Croatia, are among the best preserved in the world.
In their preliminary draft of the Neanderthal genome announced in February 2009 the scientists indicated that
"Previous mitochondrial analysis of Neanderthal DNA has uncovered no sign that Neanderthals and humans interbred sufficiently to leave a trace. A preliminary analysis across the new genome seems to confirm this conclusion, but more sequence data could overturn this conclusion" (http://www.newscientist.com/article/dn16587-first-draft-of-neanderthal-genome-is-unveiled.html#.UnKcfFCsim4. accessed 10-31-2013).
However, comparison in 2010 of the full Neanderthal sequence with that of modern humans suggested that there was some interbreeding between Homo neanderthalensis and Homo sapiens.
"Bone contains DNA that survives long after an animal dies. Over time, though, strands of DNA break up, and microbes with their own DNA invade the bone. Pääbo's team found ways around both problems with 38,000 and 44,000-year-old bones recovered in Croatia: they used a DNA sequencing machine that rapidly decodes short strands and came up with ways to get rid of the microbial contamination.
"They ended up with short stretches of DNA code that computers stitched into a more complete sequence. This process isn't perfect: Pääbo's team decoded about 5.3 billion letters of Neanderthal DNA, but much of this is duplicates, because – assuming it's the same size as the human genome – the actual Neanderthal genome is only about 3 billion letters long. More than a third of the genome remains unsequenced. . . .
"Any human whose ancestral group developed outside Africa has a little Neanderthal in them – between 1 and 4 per cent of their genome, Pääbo's team estimates. In other words, humans and Neanderthals had sex and had hybrid offspring. A small amount of that genetic mingling survives in "non-Africans" today: Neanderthals didn't live in Africa, which is why sub-Saharan African populations have no trace of Neanderthal DNA" (http://www.newscientist.com/article/dn18869-neanderthal-genome-reveals-interbreeding-with-humans.html#.UnKfSFCsim4, accessed 10-31-2013).