Granted, she says, it might take five million years to go extinct, but the process might have started in some isolated groups. What’s worse, she says we might not even notice the difference.

“As long as something came along it its stead, we would not even suspect without checking hte chromosomes,” she said.

Professor Graves has been studying sex-determining genes in Australian animals to shed light on human genetics.

“You would think that sex is so important it wouldn’t change a lot. But it changes all over the place and the Y chromosome sort of self-destructs,” she said.

The Y chromoson, which is responsible for making sperm, has gotten smaller over the years, reducint from about 1700 genes to 45.

Graves, who is thinker-in-residence at Canberra University’s Institute for Applied Ecology, notes that the Y chromosome dies out before humans become extinct, new sex-determining genes and chromosomes will evolve, perhaps leading to the evolution of a new hominid species.

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