The poorly designed Y chromosome that makes men is degrading rapidly and will disappear, even if humans are still around.

Evolutionary geneticist Jenny Graves says that while the process is likely to happen within the next five million years, it could have begun in some isolated groups.

"As long as something came along in its stead, we would not even suspect without checking the chromosomes," she said on Tuesday.

Professor Groves, who first made the prediction some years ago, was in Canberra to give a public lecture on the subject for the Australian Academy of Science.

There have been dissenting research papers, but her prediction hasn't changed.