Share 1. Those hormones regulate melanocytes — which are skin cells that produce melanin, said Dr Cameron Rokhsar, an associate clinical professor of dermatology at Mt. Sinai Medical Center in New York. When a woman is pregnant — or goes on birth control pills — she can experience heightened levels of estrogen. That increase in hormones can cause pigmentation in a woman's face.
A handful of sexual encounters between humans and Neanderthals made many of us what we are today, affecting both our appearance and our vulnerability to disease. But the genetic legacy left by the Neanderthals also highlights just how different we are from our sister species. Neanderthals lived in Europe and Asia between about , and 30, years ago. In , geneticists discovered that they had been very close neighbours indeed. Now, by studying Neanderthal genes in people alive today, researchers are beginning to appreciate how that interbreeding influenced our species. Advertisement In one new study of human genomes, Sriram Sankararaman and David Reich of Harvard Medical School and colleagues found that Neanderthal DNA is most common in regions of the genome with the greatest genetic variability, making them a prime target for natural selection.