Not only is Jenny Graves one of Australia's most influential scientists, but she is also gaining a wider reputation in the non-scientific world for her ability to convert difficult scientific concepts into language non-scientists can grasp.

Earlier this year she was awarded the distinguished Macfarlane Burnet medal for biology by the Australian Academy of Science, an honour handed out only every three years. In her Macfarlane Burnet lecture, delivered in May in Canberra, she delighted the audience with an hilarious speech explaining how studying the genes of some of Australia's most distinctly odd animals has widened our knowledge of human genetics, particularly the evolution of the sex chromosomes.

She certainly delighted those members of the audience fortunate enough to own two Xs. Tracing the evolution of the pitifully small Y chromosome with its 45 genes, she told the audience it was time to reconsider its future.

"There are two models for the Y chromosome," she said. "The model we were all brought up with was the Y as a macho little thing because if you have a Y you're male and that's it. But it turns out that's only because the Y chromosome has the SRY gene on it. The other theory is that the Y is a selfish sort of entity and it grabs genes from other parts of the genome that are handy in males.

"But our work on comparative mapping says that the Y is merely a wimp, a relic of the X chromosome. It started off being identical to the X but over millions of years it has been losing genes and there are hardly any left. This, of course, makes men very anxious."

And it's on its way out, she says. It may take 15 million years for the Y chromosome to disappear, according to Graves, but it's going to happen one way or another. "It could be tomorrow or it could be never - I think we'll probably have wiped ourselves out long before 15 million years is up," she says.

"But it's good to dream and it's funny to think that things are happening out of our control that might have very dire consequences on humans; well, the males anyway."

Next thing you know, all the women in the audience have broad smiles on their faces and the blokes are shifting uncomfortably, unnerved by the prospect of their fundamental redundancy. It certainly gets their attention.

History of research

A keynote speaker at the upcoming International Congress on Human Genetics, Graves has been studying Australia's marsupials for more than 30 years and now, through the ARC Centre for Kangaroo Genomics, heads the research into the genome of the Tammar wallaby, a gentle and pliant animal that has taught us about more than just genetic evolution. By studying this wallaby, her lab has racked up the discovery of 13 human genes - human genetics labs would be more than proud to claim just one.

One of the most important discoveries was that the gene commonly thought responsible for male sex determination, ZFY, wasn't the real deal. In humans, this gene is found on the Y and has a homologue on the X. Studying wallabies, however, showed that the ZFY is on chromosome 5 and is not the male master gene.

That discovery was made in Graves' lab by her PhD student Andrew Sinclair, who made a further breakthrough when he moved to London's Imperial Cancer Research Fund to work with Peter Goodfellow and located the real male sex-determining gene, SRY.

Back in Australia, Graves' team found another gene involved in the male sex business, RBMY, which is critical for spermatogenesis.

"RBMY's homologue is the RBMX," Graves says. "Supposedly there wasn't an X version and it was quite important to discover that there was one, because for a start it showed us that even genes that have important functions in making sperm do come from genes that have been sitting around on the X chromosome for millions of years. They are not new genes. They have just been tweaked so that they do something different."

One thing they may do is assist in embryonic brain development and this is where is gets interesting.

"We were very interested when we discovered this gene because it mapped right in the middle of a region that is deleted in some families that have X-linked mental retardation," Graves says. "So we knocked it down in the zebra fish, which is a very easy thing to do in a zebra fish embryo, and their brains just don't develop properly at all. They kind of rot away."

So if there is a link between a sex-determining gene and brain development, does that mean that men actually do think with their testicles? "That's a good question."