evolution’s fight for the y chromosome

July 19, 2009

Gentlemen, I have good news and bad news. The bad news is that the chromosome that makes us males, the Y chromosome, is deteriorating and some researchers started pondering a future in which biological males as we know them today, could be extinct. The good news is that males are vital for human reproduction and evolution so the forces of natural selection are going to try and maintain the biological setup for males as long as possible. Overly mutated Y’s are getting kicked out of the gene pool and we’re swapping genes with other chromosomes to maintain our existing distinction between the sexes.

sperm and egg

To see why this is happening, we need to go back to the first Y chromosome which was a mutation of a normal chromosome pair that gave us the modern XY setup for males and XX for females. But there’s a bit of a problem with this arrangement. The Y chromosomes couldn’t recombine with the X and speed up the editing of genetic defects, making males slightly more prone to harmful genetic conditions. Even worse, they’re losing hereditary information. Over the last 160 million years, between 800 and 900 perfectly good genes pulled a Houdini. The two things slowing the deterioration are the Y’s ability to fix itself by using the many copies of working genes in its structure when the original gets damaged, and the potential to exchange genes with other chromosomes.

So what happens in the next few million years as the Y chromosome keeps unraveling itself? Natural selection will have to kick in to preserve males. Sexual reproduction produces a much greater variety than asexual lineages which represent an extreme form of inbreeding and leave the species much more vulnerable to genetic disorders and environmental changes. This is why some scientists think that either the Y chromosome will be somehow maintained or new sex chromosomes will develop to keep males around. For humans, there’s another reason to preserve males. We can’t go the way of whiptail lizards. We either reproduce the way we always have, or go extinct as the currently slight imbalance between males and females becomes a vast rift which reduces our population by attrition. And if nature doesn’t come to the rescue, the last women on Earth can justifiably blame men for bringing an end to all of humanity.

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  • viniciuscortez

    Odd thing to know our male genes are deteriorating, but anyway, personally I don’t believe there’s only one way for us to reproduce. In fact, I believe not far from now there will be women empragnating women, by using genetic engineering – and that’s great. Scary, but great. (I’m not gay or anything, though…)

    And isn’t Y chromossome so tiny compared to other genes? It should be relatively easy to synthesize healthful copies for it, isn’t that right? (I’m speculating on a futuristic bioscience now)

  • oregonmjw

    As the apparent demise of the Y chromosome is not scheduled to occur for several million years, is it premature to discuss the going out of business sale?

    Commenter Viniciuscortez makes the observation that “there will be women impregnating women, by using genetic engineering.” Sobering thought; and, strangely, distasteful. What if something went wrong in Gene Splicing, or at the Embryo Nursery? We could end up with a third sex. The two we have now have proven more than most people can handle.

    I would prefer the traditional sperm bank approach. They have that seed repository above the Arctic Circle (although it may be a tropical beach by the time we need its content.) Every male on earth, at the very peak of his sexual prowess – around 16, I gather – would be required to donate to the Bank. Imagine the genetic diversity available in virtual perpetuity!

    The alternative, as you point out, is genetic engineering on the order the Egyptian construction of the Pyramids. Crude, time consuming, costly; but, elegant and lasting evidence of their brilliance. In a word: successful. Get on it guys.

    And if none of this works? That last woman will have tears in her eyes

  • Greg Fish

    And isn’t Y chromossome so tiny compared to other genes?

    Yes, compared to other chromosomes, the Y is awfully small. In fact, it looks like a little, shriveled X and has less than 20% of the genes, many of which are actually copies of each other.

    It should be relatively easy to synthesize healthful copies for it, isn’t that right?

    Hypothetically, yes. However, we have to ask ourselves what the consequences of doing that would be. Would the synthetic Y chromosome just unwind itself again and we’ll be right where we started? Playing around with our genetic makeup is no trivial task and every major decision like that could have profound consequences when our changes enter the gene pool and the forces of evolution take over.

  • molly

    Hi. Finally joined up. My comment is Women Rule!! However, I’ll miss you guys. LoL, big time.

  • Wow

    Wow molly, that was an extremely sexist comment. Thank you for caring about us as much as we have defended women. This is why we have the problems we do today.

  • Deadmanrose3

    Personally i belive by the time this problem actually becomes that, a problem, we would have solved it. With genetic engineering and the completion of genome mapping, fixing the Y chromosome mutation should, hypotheically, be significantly easy. Espesially considering it is the smaller easier to manipulate one of the two chromosomes. Also, if we couldn’t fix this problem, i highly doubt it would prove fatal to mankind seeing as it is much more probable we would have fallen to a disease, meteor, or simply bombing ourselves before this became an issue.

    With this said it is still an interesting fact to know that our male existence is slowly falling to a demise, even if it is not going to effect us for a while, if at all. The human is a very complex, yet young and flawed organism. This could be us adapting to something in our envioroment, another step in evolution, for all we know.

    -Interesting thought and read,
    Hunter Gregal.

  • Vicky

    I read that science is proving that men are not going to die out. It is actually evolving.
    Article: Men more evolved? Y chromosome study stirs debate