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 living relatives, 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, 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 Dr. David Page, director of the prestigious 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.