Los Angeles, CA – Neanderthals, our closest relatives, once roamed Europe and Asia before their extinction approximately 30,000 years ago. Recent genetic studies have shed light on the relationship between modern humans and Neanderthals, revealing a period of interbreeding around 47,000 years ago. However, a lingering mystery remains surrounding the absence of Neanderthal Y chromosome in modern humans.
Modern human genomes contain traces of Neanderthal DNA in nearly every part except the Y sex chromosome responsible for male development. The absence of the Neanderthal Y chromosome raises questions about its fate, whether lost accidentally, due to mating patterns, or functional deficiencies. The explanation may lie in a century-old theory regarding the health of hybrids between different species.
Neanderthals and modern humans diverged around 550,000 to 765,000 years ago in Africa, with Neanderthals migrating to Europe while our ancestors remained in Africa. The two species did not encounter each other again until modern humans arrived in Europe and Asia 40,000 to 50,000 years ago. Through well-preserved DNA from Neanderthal remains in Europe and Asia, scientists have reconstructed both male and female Neanderthal genomes, revealing genetic similarities and differences.
While modern humans carry about 2% Neanderthal DNA in their genomes, the absence of the Neanderthal Y chromosome in contemporary humans remains a puzzle. The gradual fading out of Neanderthal genes in modern populations, along with the absence of Neanderthal Y chromosome, highlights the complexity of interspecies mating and genetic inheritance. The role of the Y chromosome in hybridity and reproductive success poses intriguing questions about the evolution and divergence of Neanderthals and modern humans.
One possible explanation for the missing Neanderthal Y chromosome could lie in Haldane’s rule, which suggests that infertility or unhealthiness in hybrids often involves the sex with different sex chromosomes. The evolving nature of Y chromosomes and their interaction with other genes may have contributed to the loss of the Neanderthal Y chromosome in modern humans. This genetic mystery not only provides insight into the complex history of human evolution but also raises questions about the role of genetic compatibility in species diversification.