Neanderthals possessed the gene for language and had sophisticated music, art and tool craftsmanship skills, so they must have not been all that unattractive to modern humans at the time.
"In addition, because our methods were totally independent of Neanderthal material, we can also conclude that previous results were not influenced by contaminating artifacts," Labuda said.
This work goes back to nearly a decade ago, when Labuda and his colleagues identified a piece of DNA, called a haplotype, in the human X chromosome that seemed different. They questioned its origins.
Fast forward to 2010, when the Neanderthal genome was sequenced. The researchers could then compare the haplotype to the Neanderthal genome as well as to the DNA of existing humans. The scientists found that the sequence was present in people across all continents, except for sub-Saharan Africa, and including Australia.
"There is little doubt that this haplotype is present because of mating with our ancestors and Neanderthals," said Nick Patterson of the Broad Institute of MIT and Harvard University. Patterson did not participate in the latest research. He added, "This is a very nice result, and further analysis may help determine more details."