The 'Y' Chromosome Isn't Going Extinct

Sorry, people hoping for that world without men: The ‘Y’ chromosome isn’t going anywhere, according to a new analysis by researchers at the University of California, Berkeley.

Over the past several years, it’s become quite a fad to suggest that the shrinking Y chromosome will eventually lead to the “end of men.” There are some scientific reasons to suggest that idea isn’t totally insane: The X and Y chromosomes once shared roughly 800 genes, now they shares only 19. Overall, the X holds some 1,098 genes, the Y has just 78. Some geneticists have said that it’s only a matter of time before the Y chromosome eventually isn’t necessary at all. In fact, researchers have already created mice without a Y chromosome, and some male animals don’t have Y chromosomes at all.

“Because [Y chromosomes] can lose [a gene] … we conclude that it’s on its way to dying in humans,” Melissa Wilson, then a researcher at Penn State University, told ABC News in 2009 about a study she published in PLOS Genetics. That study suggested that it’s “unclear what is distinctive about genes that remain on the Y chromosome.”

Well Wilson, now at Berkeley, seems to have figured out the answer to that question (crazy how more investigation and time can do that). Though the Y chromosome has been getting smaller, it remains no less important to the survival of humanity. According to Wilson, the chromosome contains indispensable genes necessary for male fertility.

“Our study demonstrates that the genes that have been maintained, and those that migrated from the X to the Y are important,” Wilson said. “The human Y is going to stick around for a long while.”

Of course, most people already suspected that—previous research showed that the Y chromosome did much of its downsizing millions of years ago, and has remained stable for quite some time. That hadn’t stopped others from suggesting that mankind was eventually doomed (even though many species of animals get along fine without a Y chromosome).

Perhaps most interestingly, Wilson says there is a surprising lack of genetic diversity on Y chromosomes in general, which might actually help explain why the chromosome will remain necessary.

“Y chromosomes are more similar to each other than we expect,” she said. “There has been some debate about whether this is because there are fewer males contributing to the next generation, or whether natural selection is acting to remove variation.”

In the latest study, Wilson suggests that if natural selection weren’t at play, just one fourth of men throughout history would have had to have been fathers, a highly unlikely scenario. Instead, the Y chromosome is under extreme pressure to filter out unviable genes.

“We show that a purifying selection acting on the Y chromosome to remove harmful mutations, in combination with a moderate reduction in the number of males that are passing on their Y chromosomes, can explain low Y diversity,” she said.

So, even though the Y chromosome is much diminished, if not tiny, it has an important function and will continue to stick around in men.