Scientists have recently discovered a mechanism for genetic repair used by the Y chromosome in human males. The Y chromosome does not have a partner chromosome to pair with, and recombine with during meiosis. Recombination is one of the ways that chromosomes compensate for mutations, transcription errors, and other potentially lethal alterations; so, without the opportunity to recombine, the Y chromosome would seem extremely vulnerable, and indeed this has often been used to explain why it is so much smaller than the X chromosome, or any of the other paired chromosomes in human cells. But it turns out the Y chromosome has a way of compensating for this difficulty. Large areas of the chromosome are palindromic, that is to say, they read the same in either direction. This means that the chromosome is able to, and in fact does, fold over and recombine with itself. This explains why, although the Y chromosome has far less genes than the X or any of the other, it does in fact have something like 78 active genes, which is more than anyone expected. This discovery is interesting, although scarcely earth-shattering. But the scientists who made it cannot resist the temptation to blow it up into something far more significant than it really is: “Men and women differ by 1 to 2 percent of their genomes, Dr. Page said, which is the same as the difference between a man and a male chimpanzee or between a woman and a female chimpanzee…We all recite the mantra that we are 99 percent identical and take political comfort in it, Dr. Page said. But the reality is that the genetic difference between males and females absolutely dwarfs all other differences in the human genome.” Can Dr. Page be serious? Even if his calculations of the numbers of genes involved is correct (which I doubt), all this shows is that not all genes are equally important, or equally active. While interspecies gene comparisons can give us a sense of how closely related two species are, they do not give us any indication of how “similar” or “dissimilar” those two species are, in any meaningful sense of those words. To say that human males are as similar to chimpanzee males as they are to human females is nonsense, if only because human beings and chimpanzees cannot interbreed and produce fertile (or any) offspring. The second half of Dr. Page’s comment–with its cliched invocation of opposing “political correctness”–suggests that he is overinterpreting his results in accordance with an agenda that has nothing to do with science. All in all, I’m reminded of a witticism my brother once uttered: “Isn’t it strange that I have 98.5% of my genes in common with a chimpanzee, but only 50% of my genes in common with my own son?”
Mystique of the Y Chromosome
Scientists have recently discovered a mechanism for genetic repair used by the Y chromosome in human males. The Y chromosome does not have a partner chromosome to pair with, and recombine with during meiosis. Recombination is one of the ways that chromosomes compensate for mutations, transcription errors, and other potentially lethal alterations; so, without the opportunity to recombine, the Y chromosome would seem extremely vulnerable, and indeed this has often been used to explain why it is so much smaller than the X chromosome, or any of the other paired chromosomes in human cells. But it turns out the Y chromosome has a way of compensating for this difficulty. Large areas of the chromosome are palindromic, that is to say, they read the same in either direction. This means that the chromosome is able to, and in fact does, fold over and recombine with itself. This explains why, although the Y chromosome has far less genes than the X or any of the other, it does in fact have something like 78 active genes, which is more than anyone expected. This discovery is interesting, although scarcely earth-shattering. But the scientists who made it cannot resist the temptation to blow it up into something far more significant than it really is: “Men and women differ by 1 to 2 percent of their genomes, Dr. Page said, which is the same as the difference between a man and a male chimpanzee or between a woman and a female chimpanzee…We all recite the mantra that we are 99 percent identical and take political comfort in it, Dr. Page said. But the reality is that the genetic difference between males and females absolutely dwarfs all other differences in the human genome.” Can Dr. Page be serious? Even if his calculations of the numbers of genes involved is correct (which I doubt), all this shows is that not all genes are equally important, or equally active. While interspecies gene comparisons can give us a sense of how closely related two species are, they do not give us any indication of how “similar” or “dissimilar” those two species are, in any meaningful sense of those words. To say that human males are as similar to chimpanzee males as they are to human females is nonsense, if only because human beings and chimpanzees cannot interbreed and produce fertile (or any) offspring. The second half of Dr. Page’s comment–with its cliched invocation of opposing “political correctness”–suggests that he is overinterpreting his results in accordance with an agenda that has nothing to do with science. All in all, I’m reminded of a witticism my brother once uttered: “Isn’t it strange that I have 98.5% of my genes in common with a chimpanzee, but only 50% of my genes in common with my own son?”