27 February 2012
ByAppeared in BioNews 646
Men may not be on the brink of extinction after all, according to a study on the evolution of the human Y chromosome.
However the study, carried out by Dr Jennifer Hughes and her team at the Whitehead Institute for Biomedical Research in Massachusetts in the US, suggests that the Y chromosome may not vanish after all.
The study, published in Nature, compared the human Y chromosome to that of the rhesus monkey which is separated from humans by 25 million years of evolution. The monkey Y chromosome hasn't lost a single ancestral gene in the past 25 million years, whereas the human Y has lost just one of these ancient genes in the same period.
In a previous Nature paper, Dr Hughes and her team also compared the human Y chromosome with that of the chimpanzee, which is separated from humans by 6 million years of evolution.
Both comparative studies found that genetic decay of the human Y chromosome has been minimal, losing no further genes in the past 6 million years and only one in the past 25 million years.
'This paper simply destroys the idea of the disappearing Y chromosome', said Dr Hughes. 'Now our empirical data fly in the face of the other theories out there. With no loss of genes on the rhesus Y and one gene lost on the human Y, it's clear the Y isn't going anywhere'.
Professor Mark Pagel, Professor of Evolutionary Biology at the University of Reading, UK, told BBC News: 'It's a very nice piece of work, showing that gene loss in the male-specific region of the Y chromosome proceeds rapidly at first - exponentially in fact - but then reaches a point at which [...] this process [is brought] to a halt'.
Genetic decay of the Y chromosome has occurred because, unlike the two X chromosomes in women, there is little crossing over of genetic material between the Y and the X chromosome during reproduction.
'The X is fine because in females it gets to recombine with the other X but the Y never gets to recombine over almost its entire length, and shutting down that recombination has left the Y vulnerable to all these degenerative forces', Dr Hughes told BBC News, 'which is why we're left with the Y we have today'.
The findings have not been universally accepted. Talking to the Guardian, Professor Darren Griffin of the University of Kent, UK, maintained: 'If you draw a straight line, the Y chromosome's demise would come four or five million years from now'.
He added: 'Everyone agrees that the demise of the Y chromosome, if it happens, does not mean the demise of the human male. All that will happen is that the process of sex chromosome evolution will start again'.