The Last Man on Earth? Researchers Warn Future Looks Bleak for Y Chromosome

Darren Griffin, professor of genetics, and microbiologist Peter Ellis of Kent University, the UK, have come to believe that although the Y chromosome carries the "master switch" gene, SRY, that determines whether an embryo will develop as a male (XY) or a female (XX), it contains very few others and is not really vital. "Women, after all, manage just fine without one," the researchers wrote in a joint article for the Conversation.

They also pointed out that compared to the two normally functioning X chromosomes that women have, the men’s X is quite satisfactory, whereas the Y one has shrunken, having degraded quite severely over time. If the trend persists, the Y chromosome is predicted to disappear in about 4.6 million years, which is a relatively short time in comparison to the whopping 3.5 billion years since life came into being on planet Earth.

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The sad prediction is based on evidence that Y chromosomes have demonstrated a "fundamental flaw"– in short, there is only one Y chromosome, unlike other chromosomes which come in pairs. This means that genes carried by the Y chromosome cannot carry out genetic "shuffling", or recombination, which happens from generation to generation to prevent harmful gene mutations.

Griffin and Ellis, though, go on to say that the scenario is not quite as perilous as we might have initially imagined. They cite a recent Danish study, published in PLoS Genetics, centering around the Y chromosome’s ability to undergo pervasive structural rearrangements allowing "gene amplification", or otherwise stated, securing multiple genes that provide normal sperm functioning and, hence, reproduction.

Despite a heated debate over if the Y chromosome will actually disappear, the gene defense mechanisms obviously stand on guard. Even if it happens, Griffin and Ellis pointed out, it still does not immediately mean that men are doomed. A chromosome, other than the Y chromosome, is then thought to take on the SRY "master switch" gene that determines maleness in embryos, which thus breaks the traditional direct connection between masculinity and the Y chromosome.

"However, the new sex-determining chromosome – the one that SRY moves on to – should then start the process of degeneration all over again due to the same lack of recombination that doomed their previous Y chromosome," the researchers suggested.

They went on to say that while the Y chromosome is essential for normal human reproduction, many of its genes are not necessary if assisted reproduction techniques come into play. This raises the question of whether genetic engineering will eventually replace the function of the Y chromosome, thus bypassing natural reproduction. The latter is unlikely, the researchers concluded:

"However, even if it became possible for everybody to conceive in this way, it seems highly unlikely that fertile humans would just stop reproducing naturally."