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Scientist Says Men Will Go Extinct, Despite Debunking of "Rotting Y Chromosome Theory"

Update Date: Apr 02, 2013 04:04 PM EDT
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In the battle of the sexes, men are bound to lose, a scientist has predicted. That is, males will sooner or later go extinct.

What's more, the leading Australian scientist says the process of man's untimely end has already begun.

Evolutionary geneticist Prof. Jenny Graves said that the extinction of the male species is likely to happen within the next five million years and may have already begun in some isolated groups.

Graves said her prediction is based on the inherent fragility of the male sex chromosome, or Y sex chromosome.  She explains that the number of genes on the male chromosome is rapidly dwindling. 

The Y chromosome, which emerged around 200 to 300 million years ago started out with about 1,700 genes, has but only 45 left, and most of them are "junk", whereas the X chromosome still contains a healthy 1,000 or so genes.

What's more females have two X chromosomes, which always females to make crucial repairs by swapping between their two chromosomes. However, men only have one X chromosome and one "wimpy" Y chromosome.  Graves explains because the male Y chromosome finds it more difficult to patch up mistakes it starts to wither away.  

"The X chromosome is all alone in the male but in the female it has a friend, so it can swop bits and repair itself," she told Australian Associated Press. "If the Y gets hit, it's a downward spiral."

"You would think that sex is so important it wouldn't change a lot. But it changes all over the place and the Y chromosome sort of self-destructs," she said, according AAP.

The Y chromosome is always in the male and is mostly active in the testes making sperm, according to the Herald Sun. She explains that it is a "very dangerous place" because there is a lot of cell division going on, and with every split, there is always a chance for a mutation or gene loss.

In a public lecture, Graces said that the withering of Y is "bad news for all the men here".

The Y chromosome originally started out with as many genes as the X chromosome, but over millions of years, it has wasted away leaving less than 1 percent of its original genes in modern man.

What's even scarier, the most of the genes left in the Y chromosome is "junk".  

"It is a lovely example of what I call dumb design," she told AAP. "It is an evolutionary accident."

However, Graves notes that the eventual extinction of man will still take about another five million years.

If humans don't die off, new sex-determining genes may evolve and lead to the evolution of a new hominid species, Graves said. For instance, this process happened in the Japanese spiny rat, which survived the loss of its Y chromosome.

However, other experts disagree with Graves' theory.

In a study published last year in the journal Nature, U.S. researchers found evidence to debunk the "so-called rotting Y theory" that assumed the human Y chromosome will continue to rapidly decay genetically until it has no genes.  Researchers at MIT compared the Y chromosome of the rhesus macaque, which shares common ancestors with chimpanzees and modern humans, to the chimpanzee and human Y chromosome sequences and found that humans had only lost one gene from the Y chromosome since the time the rhesus macaque and people took on separate evolutionary paths 25 million years ago. Researchers said their findings suggest that the human Y chromosome may not lose anymore of its remaining genes.

"The Y was in free fall early on, and genes were lost at an incredibly rapid rate," said researcher Whitehead Institute Director David Page, according to Medical Daily. "But then it leveled off, and it's been doing just fine since."

Researchers explained that with no further loss of genes on the rhesus Y, which is similar to the human Y, men should feel comforted that their Y chromosome won't be going anywhere.

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