Male Y chromosome extinction theory challenged

By | February 23, 2012

Men may not become extinct after all, according to a new study.

Previous research has suggested the Y sex chromosome, which only men carry, is decaying genetically so fast that it will be extinct in five million years’ time.

A gene within the chromosome is the switch which leads to testes development and the secretion of male hormones.

But a new US study in Nature suggests the genetic decay has all but ended.

Professor Jennifer Graves of Australian National University has previously suggested the Y chromosome may become extinct in as little as five million years’ time, based on the rate at which genes are disappearing from the chromosome.

Genetics professor Brian Sykes predicted the demise of the Y chromosome, and of men, in as little as 100,000 years in his 2003 book Adam’s Curse: A Future without Men.

The predictions were based on comparisons between the human X and Y sex chromosomes. While these chromosomes were once thought to be identical far back in the early history of mammals, the Y chromosome now has about 78 genes, compared with about 800 in the X chromosome.

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The Y is not going anywhere and gene loss has probably come to a halt”

Dr Jennifer Hughes Whitehead Institute, Cambridge, Massachusetts

Jennifer Hughes and colleagues at the Whitehead Institute in Cambridge, Massachusetts, have sought to determine whether rumours of the Y chromosome’s demise have been exaggerated.

In a previous Nature paper in 2005, they compared the human Y chromosome with that of the chimpanzee, whose lineage diverged from that of humans about six million years ago.

They have now sequenced the Y chromosome of the rhesus monkey, which is separated from humans by 25 million years of evolution.

The conclusion from these comparative studies is that genetic decay has in recent history been minimal, with the human chromosome having lost no further genes in the last six million years, and only one in the last 25 million years.

“The Y is not going anywhere and gene loss has probably come to a halt,” Ms Hughes told BBC News. “We can’t rule out the possibility it could happen another time, but the genes which are left on the Y are here to stay.

“They apparently serve some critical function which we don’t know much about yet, but the genes are being preserved pretty well by natural selection.”

via BBC News – Male Y chromosome extinction theory challenged.

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