The Y chromosome that makes men is poorly designed and degrading rapidly, meaning it's likely to disappear even while humans remain on the planet, an evolutionary geneticist and "thinker in residence" at a leading Australian college says.
Professor Jenny Graves from the Research School of Biology at the Australian National University in Canberra, has repeated her controversial prediction made some years ago while giving a public lecture on the subject for the Australian Academy of Science.
Graves first heralded the "death" of the Y chromosome in a 2009 speech titled "The Decline and Fall of the Y Chromosome, and the Future of Men."
The speech suggested that the male Y chromosome could run out within the next five million years, which is a snap in evolutionary terms.
She told medical students at the annual outreach public lecture at the Royal College of Surgeons (RCSI) in Ireland that a second species of human beings could even be born in the future.
"You need a Y chromosome to be male. Three hundred million years ago the Y chromosome had about 1,400 genes on it, and now it's only got 45 left, so at this rate we're going to run out of genes on the Y chromosome in about five million years. The Y chromosome is dying and the big question is what happens then."
The good news, she said, was that certain rodent species — found chiefly in Eastern Europe and Japan — had no Y chromosome nor the gene (SRY) that switched on the development of testis and pumped out male hormones.
"Yet there are still plenty of healthy male mole voles and country rats running around. Some other gene must have taken over the job and we'd like to know what that gene is."
A report debunking the "rotting Y" theory was published in the journal Nature in 2012.
Yet despite that and other dissenting research papers, Graves' prediction had not changed, the Australian Associated Press reported.
Describing the Y chromosome as an "evolutionary accident," she told her audience at the Academy:
"It's very bad news for all the men here."
Graves said that in her research on "Australia's unique mammals," she had determined that the Y chromosome was active mostly making sperm in the testes, which was a "very dangerous" place owing to the constant division of cells.
With every split, there was a chance for a mutation or gene loss, whereas:
"The X chromosome is all alone in the male, but in the female it has a friend so it can swap bits and repair itself. If the Y gets a hit it's a downward spiral."