In the recent years, researchers have made significant progress in understanding the genetic history of Neanderthals by sequencing the Y chromosome of male Neanderthals. Most previous studies had primarily focused on female remains, leaving the male genetic history largely unknown.
However, in a recent collaborative effort, scientists have identified male-specific DNA sequences from the remains of three Neanderthals found in Russia, Spain, and Belgium, dating back approximately 38,000 to 53,000 years ago. Upon comparison of these sequences with those of the Denisovans, researchers discovered that they resembled to another ancient human group, represented by remains from Siberia dating back 70,000 to 120,000 years ago.
Surprisingly, the Y chromosome of Neanderthals was found to be more similar to that of modern humans than the Denisovans, suggesting that a genetic exchange occurred after the Neanderthals and Denisovans diverged. Though the reasons for this exchange are unclear, it is speculated that the Neanderthal Y chromosome may have had lower evolutionary fitness, leading to natural selection favouring the Y chromosomes from early modern humans.
Computer simulations suggest that because of the repeated inbreeding among Neanderthal populations, several problematic mutations could have arisen. This could have led to the introduction of a more robust Y chromosome from humans that could possibly have been responsible for providing advantages like that in agility, and fertility – that ultimately resulted in its replacement. The study highlights the challenges in studying ancient male bones and suggests that further research on Neanderthal Y chromosome sequences may shed light on their genetic history.