Of Monkeys and Men


When frustrated with the opposite sex, women tend to compare men to monkeys, apes, or even chimpanzees.  However, judging from recent discoveries concerning the Y chromosome in men and chimpanzees, scientists from the Whitehead Institute at MIT and the Genome Center at Washington University might argue that this comparison has no scientific basis (NY Times coverage).

The Y chromosome is the unit of DNA that makes men, men.  While women carry two X chromosomes, men carry one X and one Y.  After decoding the DNA sequence of the chimpanzee Y chromosome, Whitehead Institute researchers discovered that the human and chimpanzee Y chromosomes are surprisingly dissimilar.

In particular, they found that the DNA content, or the “genes,” of the Y chromosomes differ by 30%.  Remarkably, the remainder of human and chimp DNA differs by less than 1%! Additionally, the chimp Y chromosome contains more repetitive DNA and less functional DNA than its human counterpart, making human Y chromosomes more complex. These discrepancies indicate that the Y chromosome has been rapidly evolving since humans split from chimpanzees—and more rapidly than the rest of the human and chimp DNA.

So why would the Y chromosome change more quickly?  One explanation is that there is intense selective pressure on Y chromosomal genes because they control sperm production.  If a certain gene yields better, fitter sperm, the Y chromosome containing that gene will be more frequently passed on to offspring.  Other genes, whether beneficial or not, will “hitchhike” a ride along with these good sperm production genes.  Thus, genes on the Y chromosome can easily spread throughout a population.

But I think these scientists have a bigger question to tackle: If human Y chromosomes are more complex than those of chimps, then can women rightfully criticize men for acting like their primate ancestors?

-blog authored by Alex Gast



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