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Male pride: scientists report halt in decay of the Y chromosome

Over millions of years, the Y chromosome – which makes men… men – had begun to shrink, and risk total extinction.

The 'rotting Y' theory suggested that the presence of more baby girls than boys was as a result of genetic mutations.
The 'rotting Y' theory suggested that the presence of more baby girls than boys was as a result of genetic mutations.
Image: Karim Kadim/AP

SCIENTISTS HAVE AFFIRMED that men aren’t going to be written out of history just yet – after affirming that the decline in the Y chromosome appears to have stalled.

A study published yesterday has put paid to the theory that evolution was writing men out of existence – after scientists noted, around a decade ago, observed that the presence of the chromosome had waned over time.

Writing in the latest issue of Nature, a team of researchers led by Prof Jennifer Hughes of MIT say that the decline of the Y chromosome – the very thing which makes men… well, men – has been arrested.

Their research – which finds that the decline in the Y chromosome seems to have reached a plateau – ends the ‘rotting Y theory’ in which it was thought that the Y chromosome would continue to wane until it simply disappeared.

The study involved examining the human genome and comparing it with the rhesus macaque monkey, which diverged from humans on an evolutionary basis 25 million years ago.

It found that humans had only lost one ancestral gene – accounting for three per cent of the entire genome – while the rhesus has not lost any such gene at all.

The Daily Telegraph quotes Hughes as saying:

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.

Although Hughes acknowledges that the Y chromosome had initially waned, saying genes were lost from the chromosome at “an incredibly rapid rate”, it has now reached a level of ‘strict conservation’ – and has been there for some 25 million years.

The falling presence of the Y chromosome, when compared to the X chromosome which leads to female offspring, had been put forward as the reason why the birth rates of baby girls were higher than those of baby boys.

The X and Y chromosomes form one of 23 pairs of chromosomes that form the human genome – with a pair of XX chromosomes meaning a female child, and an XY pairing meaning a male.

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Gavan Reilly

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