Genetic information has lent us vital clues as to the departure line between humans and Neanderthals.
A journal recently published a study concerning the Y chromosome in Neanderthals. This lends us important clues about the differences between Neanderthals and humans and how their lineages never coincided. This Y chromosome was the last feature to be identified in Neanderthals.
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The populations diverged at one point and Neanderthals went their way while homo sapiens went theirs. This study also helps us go deep into genetic interactions between old and new gene variants in hybrid offspring.
"Characterizing the Neanderthal Y chromosome helps us to better understand the population divergence that led to Neanderthals and modern humans," says Fernando Mendez of Stanford University. "It also enables us to explore possible genetic interactions between archaic and modern [gene] variants within hybrid offspring."
A Neanderthal found in El Sidron, Spain had its Y chromosome analyzed in the lab. Mendez and his colleagues, including Carlos Bustamante, also at Stanford, and Sergi Castellano, from the Max Planck Institute for Evolutionary Anthropology in Germany, analyzed that Y chromosome.
The evidence shows that Neanderthals and humans went their separate ways 590,000 years ago. This particular Y chromosome in Neanderthals is very different from such chromosomes in human beings.
Thus the lineage of this Y chromosome must be extinct for all purposes. Various protein-coding differences between the two were also found. Three changes include mutations on a genetic level.
These mutations produce male-specific minor histocompatibility antigens. The antigens of one of these genes termed KDMSD cause an immune response in gestating mothers. This causes their male fetuses to be aborted naturally.
These incompatibilities at the genetic level may have led to ancient humans and Neanderthals diverging and never interbreeding with one another. T
he Y chromosome may have been the main factor that disallowed miscegenation that went against the genetic flow. These changes in functional genes rather than those genes that play a role in sperm production come as somewhat of a shock.
"The functional nature of the mutations we found suggests to us that the Y chromosome may have played a role in barriers to gene flow," Bustamante says.
"The finding that most of the functional differences associate with these genes, rather than with genes involved in [sperm production], came as a surprise," Mendez adds.
More studies would be needed that delve deep down into this Y chromosome misalignment and come up with valuable data concerning the split between homo sapiens and Neanderthals.
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These findings were reported in the American Journal of Human Genetics published by Cell Press.