Scientists: Male Chromosome Is Still Evolving

DEBORAH AMOS, host:

And now some good news about men. Scientists have confirmed that they are still evolving, or at least the male chromosome is. NPR's Jon Hamilton explains.

JON HAMILTON: The male or Y chromosome is what makes men men. A few years ago, scientists began wondering whether it was in trouble. When they compared it to the X chromosome, which is carried by both men and women, the Y chromosome didn't seem to measure up. David Page, who directs the Whitehead Institute at MIT, says the contrast was pretty stark.

Professor DAVID PAGE (Whitehead Institute, MIT): The X chromosome standing tall, robust with many hundreds of genes, the human Y chromosome just a hollow shell of its former glory carrying on the order of 70 or 80 genes.

HAMILTON: For hundreds of millions of years, the Y had evolved by getting rid of genes. And that type of evolution can't go on forever. So Page decided there was something he needed to know about the Y chromosome.

Prof. PAGE: Was it really simply a victim of an inevitable, faded demise, or had it developed some new tricks along the way?

HAMILTON: To find out, he and a team of researchers compared the Y chromosome of a person to that of a chimp. Page says it turned out that both Ys had been evolving really fast for the past six million years or so.

Prof. PAGE: It's as if the Y chromosome is a house that's constantly being reconstructed or remodeled.

HAMILTON: A house without too many rooms, but there's a lot going on - more, actually, than in chromosomes with many more genes. Page says that's possible, because the Y chromosome contains unusual stretches of DNA that work like Tinker Toys. They're easy to pull apart, flip around and reassemble for a new purpose.

Prof. PAGE: It shows quite a degree of inventiveness and creativity that maybe the rest of the genome could learn something from.

HAMILTON: Like how to make the most of the genes you've got. The study appears in the online edition of the journal Nature.

Jon Hamilton, NPR News. Transcript provided by NPR, Copyright National Public Radio.