Sunlight Adaptation in Humans Inherited from Neanderthals

It turns out that we may have even more in common with Neanderthals than we thought. Scientists have already discovered that humans and Neanderthals once interbred, but now they're piecing together the specifics to find out exactly what traits persist in modern humans.

Scientists have published the Neanderthal genome, revealing that about 5 percent of Neanderthal DNA can be found in humans. But are there advantages to the retention of Neanderthal DNA that favors modern humans? In order to find that out, the researchers examined the DNA a bit more closely.

The scientists found evidence of a Neanderthal DNA region found on chromosome 3 that contains 18 genes, with several related to UV-light adaptation. One of these genes was the Hyal2 gene. In fact, the scientists showed that this region was positively selected and enriched in East Asians, ranging from up to 49 percent in Japanese to 66 percent in Southern Chinese.

That's not all the researchers found, though. They also discovered that the geographic distribution of the Neanderthal genomic region suggests that UV-light mutations were lost during the exodus of modern humans from Africa. These mutations were then reintroduced to Eurasians from Neanderthals.

In fact, from 45,000 to 5,000 years before the present, effective population sizes of the Neanderthal region increased at a steady rate. Notably, the growth rate of the effective population size increased at around 5,000 to 3,500 years before present. This suggests a population expansion event. This Asian-specific Neanderthal evolution event is also consistent with previous reports of higher levels of Neanderthal ancestry in East Asians than in Europeans.

"Overall, it is still very controversial whether this is more Neanderthal DNA contributions to Asians than Europeans, as we have evidence to argue against this," said Lin, one of the researchers, in a news release. "Although in the case of the Hyal2 variant, it did indeed have a higher frequency in Asians."

The findings are published in the journal Molecular Biology and Evolution.