Are Men Becoming Extinct?

The world can breathe a little easier today: despite the worries of some scientists, it seems the Y chromosome isn’t withering away after all.

While the Y and X — male and female — chromosomes once had roughly 800 genes in common, the Y now carries just 19 of its ancestral genes, knocking it down to a fraction of its original size. This sounded the alarm with some researchers, who feared the degeneration would continue and eventually make the Y chromosome — and men — disappear altogether.

But not so, says study researcher Jennifer Hughes from Whitehead Institute in Cambridge, MA. In work published Tuesday in journal Nature, she and her colleagues found the shedding has reached a plateau and likely won’t continue. They sequenced the genome of the rhesus macaque, an ancient monkey whose lineage split from that of humans 25 million years ago but whose Y chromosomes are remarkably similar to men’s.

The results showed that reports of the chromosome’s decay have been largely exaggerated. Hughes told LiveScience, “For the most part, the gene content has not changed for 25 million years … The rate of decay appears to have just basically ceased at this point.”

Next, Hughes hopes to trace the evolution of the male chromosome back even further, but for now, she says, “[It's clear] the Y is not going anywhere.”