Male Chromosome on the Way Out

The Y chromosome’s days are numbered and its demise could lead to the creation of a new human species, predicts Jenny Graves, a professor of comparative genomics at the Australian National University. The Y chromosome started with about 1400 genes – but has lost about 1350 over the last 300 million years, says Graves, who believes the degrading chromosome will eventually be replaced by new male-determining genes on other chromosomes. She has been intrigued by studies of Y-less rodents who appear male and have not lost their ability to reproduce. They have replaced the SRY gene – the only “strong” male gene – with something else, but we don’t know what it is yet, Graves says. Should this gene replacement occur in one human population, two groups with different reproductive systems could not mate and would gradually become different species.