Why a shrinking Y chromosome still doesn't mean the end of men

Is the Y chromosome really headed towards disappearing? Well, perhaps (give or take 10 million years or so.) But most likely not.

In a Q&A today with science historian Sarah Richardson on genetics and sex differences, commenter decemberfifthburner asked about reports that the Y chromosome could be headed for extinction. The Y chromosome doesn't use standard recombination for repairs, says Richardson, hence the concern over shedding genes. But new research shows that the Y-chromosome is using a recombination-like process to make repairs:

It's certainly a fact that the evolution of the Y chromosome (from its original status as an X chromosome), because it is passed clonally from male to male and does not repair through standard recombination, has involved the sloughing off hundreds of genes. This is true in every sex chromosome system – over millions of years, the clonally inherited chromosome in the sex chromosome pair loses its function other than sex determination and diminishes in size and gene count. Now, is the human Y chromosome going extinct? In some species of voles, it already has, so it's certainly a theoretical possibility.

But why are we so concerned about this now? The Y going extinct isn't happening any time soon, if it all (estimates run in the 10 million years+ range). And, as in voles, the disappearance of the Y doesn't, in principle, mean the loss of the male sex. David Page at MIT has discovered that recombination-like processes in the Y chromosome ("gene conversion") may help repair the human Y and be keeping it in a holding pattern from further degeneration.

So, with a repair process in sight and a timeline measured in millions, just why has the idea of a disappearing Y-chromosome captured the public imagination? Richardson says it may have more to do with culture than research:

I think the popular concern about the status of the Y is continuous with concerns about the decline of men in a postfeminist age and with other biologistic discourses about males sperm count decline and males' lack of evolutionary adaptation to the supposedly "feminized" environment of the post-industrial workforce. Y chromosome degeneration theories are truly a node where a good understanding of the cultural gender context helps understand the shape of the scientific debate.

Image: Sebastian Kaulitzki /Shutterstock