Neanderthals, our closest relatives, lived in Europe and Asia until they went extinct 30,000 years ago. Recent genetic studies have uncovered more about the connections between modern humans and Neanderthals. It was discovered that there was a surge of interbreeding between the two species around 47,000 years ago. However, a mystery still remains.
Modern humans have a small amount of Neanderthal DNA in their genomes, but interestingly, this DNA is absent from the Y sex chromosome responsible for male development. The absence of Neanderthal DNA in the Y chromosome raises questions about what happened to it. It could have been lost accidentally, due to mating patterns, or because it was not functioning as well. An old theory suggests that interspecies hybrids may have health issues, shedding light on the possible fate of the Neanderthal Y chromosome.
Neanderthals and modern humans diverged from a common ancestor between 550,000 and 765,000 years ago in Africa. Neanderthals moved to Europe while modern humans remained. They reunited when modern humans migrated to Europe and Asia 40,000 to 50,000 years ago. Scientists have reconstructed the full Neanderthal genome from DNA found in well-preserved bones and teeth. The Neanderthal genome closely resembles that of modern humans, with 20,000 genes distributed across 23 chromosomes.
While most of the Neanderthal genome has been sequenced, the Y chromosome remains a challenge due to its repetitive DNA. What has been sequenced shows similarities to the modern human Y chromosome, including a gene called SRY responsible for male development. This suggests that Neanderthals likely had a similar sex-determining gene, even though the exact gene has not been found.
Interbreeding between Neanderthals and modern humans left a genetic mark in our DNA, with European lineages containing about 2% Neanderthal DNA. The influx of Neanderthal DNA occurred around 47,000 years ago, coinciding with modern humans’ migration to Europe. Interestingly, no modern humans have been found with Neanderthal Y chromosome, raising questions about its fate.
Several theories speculate on the disappearance of the Neanderthal Y chromosome. It could have been lost due to a lack of sons carrying the Y chromosome, or it may not have been present in interspecies matings. The Y chromosome could have been less effective at its job compared to the modern human Y chromosome, leading to its disappearance over generations.
Another possibility is that the Neanderthal Y chromosome was incompatible with genes from modern human chromosomes, following a genetic rule known as Haldane’s rule. This rule suggests that hybrids between species are often infertile or unhealthy, especially the sex with different sex chromosomes. The rapid evolution of Y chromosome genes may have contributed to the disappearance of the Neanderthal Y chromosome.
In conclusion, the mystery of the missing Neanderthal Y chromosome raises intriguing questions about the genetic interactions between Neanderthals and modern humans. Further research may provide more insights into the fate of the Neanderthal Y chromosome and its implications for our understanding of human evolution.