January 18, 2010--Sperm Olympics
I’m worried about my manhood. Not actually mine, but rather man’s manhood.
A year ago, I was worried that men were in danger of becoming biologically obsolete. That the chromosome which is responsible for fetuses turning into men, the Y chromosome, was literally shrinking; and before too much longer, some scientists claimed, man will become biologically obsolete and sexually reproduction as we know it will cease.
Our Y chromosomes have been losing genes. When homo sapiens first evolved, X and Y chromosome started out with about the same number of genes -- about 1,000. Today, however, the Y chromosome has less than 80 genes; and in about another million years, we’ll be down to zero.
Though by this calculus we shouldn’t be that worried about such matters for, say, at least the rest of this millennium, things are not looking too good when it comes to our longer-term destiny. And, more promising, other scientists are seeing things differently. For example, David Page of MIT's Whitehead Institute claims, "At the same time that the Y chromosome is continuing to lose genes, it's found some new ways of replenishing itself."
And also last year, Page and his colleagues reported a finding that brought me some cheer--at the same time as it has been shedding genes, the Y chromosome has been secretly creating backup copies of its most important ones. These are being stored in the DNA as mirror images of the disappearing genes. According to this scenario, there is hope for maleness after all, and thus for the human race, such as it is.
In spite of these hopeful thoughts of Dr. Page, it has taken me some time to get used to the idea that the potency of my future male brethren is likely winding down.
But now the good doctor has me totally confused.
At the same time that men are in danger of no longer being men and whatever consequences that might have for species survival, from him and his colleagues, I am now learning that that our species is undergoing another kind of change. Our Y chromosome is experiencing a much more rapid, different kind of metamorphosis.
According to a recent article in the New York Times (linked below), after Dr. Page finished decoding the DNA of our closest relative, the chimpanzee, he found evidence that since about six million years ago, a mere blink of the eye in evolutionary time, change to man’s Y chromosome has been rampaging ahead at such a rapid rate that it is now 30 percent different than a chimpanzee’s. While the rest of our genome has remained pretty much chimp-like, this male-determining chromosome is startlingly different.
To add to my confusion, it appears that though chimpanzee Y chromosomes have also evolved more rapidly than other parts of their genome, this change has been decidedly slower than human’s.
How to explain this, and does this offer more hope for our long-term survival, assuming we do not do ourselves in in other ways before that one-million-year biological time clock runs down?
Again, according to Dr. Page these unexpectedly rapid changes are the result of chimp and, yes, human mating habits. Things now are about to get a little more delicate.
When a female come into heat, she mates with all the males in the group, in effect setting up competition within her uterus for all the males’ sperm. Which one, or which ones, will cause conception? In evolutionary terms, the winners will not be determined just by chance. The sperm which wiggle the fastest and are the strongest swimmers will find their way first to her ovum and fertilize one or more of them, and this sperm vitality and potential to survive will be passed along to their offspring.
You may be wondering what does this have to do with our own kind. What chimps do chimps do; but we are humans and this is not the way we mate. It may be the way some of us fool around, but mating is something different.
Well, Dr. Page relentlessly points out, not so fast.
First of all, we have been fully emerged homo sapiens for only 200,000 years and, in regard to how we carried on in the savannahs and caves, who knows what was going on for the first 195,000. And even now, he cannot help himself from pointing out, there are contemporary examples of heteropaternity—the birth of twins with two different fathers.
So even though the primate Sperm Olympics is still going on among other apes in the wild, at least when it comes to us, though some of our behavior has evolved as the result of our relatively new-fangled moral and religious codes, it appears that there is still extant evidence from these twins of that earlier kind of more unrestrained behavior. And thus, for species survival sake, as well as for that of the fragile, incredibly-shrinking homo sapien Male Ego, on this bleak Monday, there is cause for some muted optimism.
A year ago, I was worried that men were in danger of becoming biologically obsolete. That the chromosome which is responsible for fetuses turning into men, the Y chromosome, was literally shrinking; and before too much longer, some scientists claimed, man will become biologically obsolete and sexually reproduction as we know it will cease.
Our Y chromosomes have been losing genes. When homo sapiens first evolved, X and Y chromosome started out with about the same number of genes -- about 1,000. Today, however, the Y chromosome has less than 80 genes; and in about another million years, we’ll be down to zero.
Though by this calculus we shouldn’t be that worried about such matters for, say, at least the rest of this millennium, things are not looking too good when it comes to our longer-term destiny. And, more promising, other scientists are seeing things differently. For example, David Page of MIT's Whitehead Institute claims, "At the same time that the Y chromosome is continuing to lose genes, it's found some new ways of replenishing itself."
And also last year, Page and his colleagues reported a finding that brought me some cheer--at the same time as it has been shedding genes, the Y chromosome has been secretly creating backup copies of its most important ones. These are being stored in the DNA as mirror images of the disappearing genes. According to this scenario, there is hope for maleness after all, and thus for the human race, such as it is.
In spite of these hopeful thoughts of Dr. Page, it has taken me some time to get used to the idea that the potency of my future male brethren is likely winding down.
But now the good doctor has me totally confused.
At the same time that men are in danger of no longer being men and whatever consequences that might have for species survival, from him and his colleagues, I am now learning that that our species is undergoing another kind of change. Our Y chromosome is experiencing a much more rapid, different kind of metamorphosis.
According to a recent article in the New York Times (linked below), after Dr. Page finished decoding the DNA of our closest relative, the chimpanzee, he found evidence that since about six million years ago, a mere blink of the eye in evolutionary time, change to man’s Y chromosome has been rampaging ahead at such a rapid rate that it is now 30 percent different than a chimpanzee’s. While the rest of our genome has remained pretty much chimp-like, this male-determining chromosome is startlingly different.
To add to my confusion, it appears that though chimpanzee Y chromosomes have also evolved more rapidly than other parts of their genome, this change has been decidedly slower than human’s.
How to explain this, and does this offer more hope for our long-term survival, assuming we do not do ourselves in in other ways before that one-million-year biological time clock runs down?
Again, according to Dr. Page these unexpectedly rapid changes are the result of chimp and, yes, human mating habits. Things now are about to get a little more delicate.
When a female come into heat, she mates with all the males in the group, in effect setting up competition within her uterus for all the males’ sperm. Which one, or which ones, will cause conception? In evolutionary terms, the winners will not be determined just by chance. The sperm which wiggle the fastest and are the strongest swimmers will find their way first to her ovum and fertilize one or more of them, and this sperm vitality and potential to survive will be passed along to their offspring.
You may be wondering what does this have to do with our own kind. What chimps do chimps do; but we are humans and this is not the way we mate. It may be the way some of us fool around, but mating is something different.
Well, Dr. Page relentlessly points out, not so fast.
First of all, we have been fully emerged homo sapiens for only 200,000 years and, in regard to how we carried on in the savannahs and caves, who knows what was going on for the first 195,000. And even now, he cannot help himself from pointing out, there are contemporary examples of heteropaternity—the birth of twins with two different fathers.
So even though the primate Sperm Olympics is still going on among other apes in the wild, at least when it comes to us, though some of our behavior has evolved as the result of our relatively new-fangled moral and religious codes, it appears that there is still extant evidence from these twins of that earlier kind of more unrestrained behavior. And thus, for species survival sake, as well as for that of the fragile, incredibly-shrinking homo sapien Male Ego, on this bleak Monday, there is cause for some muted optimism.
posted by Steven Zwerling at
6:27 AM
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