Men are on the road to extinction as their genes shrink and slowly fade away, claims British professor Jennifer Graves.
The researcher in human sex chromosomes said the male Y chromosome was dying and could run out within the next five million years.
But Professor Graves said men may follow the path of a type of rodent which still manages to reproduce despite not having the vital genes that make up the Y chromosome.
She told medical students at the annual outreach public lecture at the Royal College of Surgeons (RCSI) in Ireland a second species of human beings could even be born in the future.
“You need a Y chromosome to be male,” said Prof Graves.
“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 male Y chromosome has a gene (SRY) which switches on the development of testis and pumps out male hormones that determine maleness.
In her lecture, entitled The Decline and Fall of the Y Chromosome and the Future of Men, Prof Graves discussed the disappearance of the Y chromosome and the implications for humans.
She said it was not known what would happen once the Y chromosome disappeared.
“Humans can’t become parthenogenetic [asexually reproduce], like some lizards, because several vital genes must come from the male,” she continued.
“But the good news is that certain rodent species – the mole voles of Eastern Europe and the country rats of Japan – have no Y chromosome and no SRY gene.
“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.”
Prof Graves is from the Australian National University, Canberra.