The Y chromosome is disappearing: What does this mean for the future?

The male gene could be close to extinction

Illustration of human chromosomes, a DNA helix, and genetic data
There is also the possibility that humans will develop an entirely new sex gene
(Image credit: Illustration by Stephen Kelly / Getty Images)

Human biological sex is determined by the sex chromosomes X and Y. In most cases, females possess two X chromosomes, while males have one X and one Y. However, there is some evidence that the Y chromosome is being phased out of the evolutionary pipeline, and could one day disappear altogether — potentially giving rise to a new sex gene in the process.

Why is the Y chromosome disappearing?

Males tend to only have one copy of the Y chromosome, so it does not have the opportunity to go through genetic recombination, or the "shuffling of genes that occurs in each generation which helps to eliminate damaging gene mutations," Darren Kent, a professor at the University of Kent and Peter Ellis, a lecturer at the University of Kent, said at The Conversation. Without recombination, Y chromosomal genes degenerate over time. "This significant gene loss over the centuries has led scientists to predict that the Y chromosome might vanish entirely in about 11 million years," said Earth.com.

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What are the implications?

The most important part of the Y chromosome is the master sex gene called SRY, which triggers a fetus' development as a biological male. "The X and Y were once upon a time just an ordinary pair of chromosomes. Then one partner acquired a variant gene (SRY) that determines maleness," Graves said to Newsweek. So what happens if the Y disappears? "When humans run out of Y chromosome, they might become extinct (if we haven't already extincted ourselves long since), or they might evolve a new sex gene that defines new sex chromosomes." Rest assured, this type of evolution will take millions of years.

Some clues may be found in rats. "We could simply evolve a new sex-determining gene. That's what we've already seen happen in some types of rodents, and it seems to have worked successfully," said Graves to Science Focus. A 2022 study published in the journal PNAS found that the important Y chromosome genes could be capable of relocating to other genes, as observed in mice. There is also the possibility that humans develop an entirely new sex gene. "This evolutionary change could have profound implications for human evolution," said the Economic Times. "Scientists caution that the development of multiple sex-determining systems in different human populations could lead to the emergence of new human species."

Still, human males are not going away any time soon. Some experts firmly believe that the Y chromosome will not disappear at all, claiming that it has several defense mechanisms in place. A 2017 study published in the journal PLOS Genetics said the chromosome's evolution of palindromes — DNA sequences that read the same forward as backward — and repetitive copies of genes could keep it from degrading faster by allowing "damaged genes to be repaired using an undamaged back-up copy as a template." On a positive note, "by embracing ongoing research and understanding the complexities of genetics, we can find reassurance in the resilience of our species," said Earth.com.

Devika Rao, The Week US

 Devika Rao has worked as a staff writer at The Week since 2022, covering science, the environment, climate and business. She previously worked as a policy associate for a nonprofit organization advocating for environmental action from a business perspective.