Study Reveals Predominant Interbreeding Between Neanderthal Males and Human Females

A recent study published in Science reveals that interbreeding between Neanderthals and modern humans predominantly occurred between Neanderthal males and human females. Researchers from the University of Pennsylvania analyzed genomic data from three female Neanderthals who lived approximately 122,000, 80,000, and 52,000 years ago. They discovered that while most of the Neanderthal genome lacked human DNA, the Neanderthal X chromosome contained a significant amount of modern human DNA.

Modern humans and Neanderthals shared a common ancestor around 600,000 years ago, after which their lineages diverged. Between 100,000 and 70,000 years ago, a group of modern humans migrated out of Africa, encountering Neanderthals in regions of West Asia, Asia, and Europe. These interactions led to interbreeding events, resulting in the presence of Neanderthal DNA in modern human genomes.

The study found that Neanderthal X chromosomes had 62% more modern human DNA compared to their autosomal chromosomes. This suggests that Neanderthal males mated more frequently with human females than the reverse. The researchers propose that this pattern may be due to mating preferences or social structures of the time. The exact reasons for this bias remain uncertain, but the findings provide insight into the complex interactions between these ancient populations.

These results challenge previous assumptions that the scarcity of Neanderthal DNA on the human X chromosome was due to natural selection removing harmful Neanderthal genes. Instead, the study suggests that behavioral factors played a significant role in shaping the genetic landscape of modern humans.