WASHINGTON — Women may think of men as primitive, but new research indicates that the Y chromosome — the thing that makes a man male — is evolving far faster than the rest of the human genetic code.
A new study comparing the Y chromosomes from humans and chimpanzees, our nearest species, show that they are about 30 percent different. That is far greater than the 2 percent difference between the rest of the human genetic code and that of the chimp's, according to a study appearing online Wednesday in the journal Nature.
These changes occurred in the last 6 million years or so, the researchers said, relatively recently when it comes to evolution.
"The Y chromosome appears to be the most rapidly evolving of the human chromosomes," said study co-author David Page, director of the Whitehead Institute in Cambridge and a professor of biology at MIT. "It's an almost ongoing churning of gene reconstruction. It's like a house that's constantly being rebuilt."
Before men get too impressed with themselves, lead author Jennifer Hughes offers some words of caution: Just because the Y chromosome, which determines gender, is evolving at a speedy rate, it doesn't necessarily mean men themselves are more evolved.
Researchers took the most detailed examination of the Y chromosome, which females do not have, of both humans and chimps and found entire sections dramatically different. There were even entire genes on the human Y chromosome that weren't on the chimp, said Hughes, also of the Whitehead Institute.
The two-year research took twice as long as expected because of the evolutionary changes found, Hughes said.
There is a bit of a proviso to the comparison to other chromosomes. While all human and chimp chromosomes have been mapped, only two chimp chromosomes have been examined in great detail: Y and chromosome 21. Yet, there's still enough known to make the claim that the Y is the speediest evolver, Hughes and Page said.
Outside scientists praised the study.
"Wow," said R. Scott Hawley, a genetics researcher at the Stowers Institute in Kansas City. "That result is astounding."
"The Y chromosome clearly has the strength and tenacity to fight back," said Hawley, who wasn't part of the research.