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.