Female baboons' big red bottoms are not just showy ploys to attract mates, according to new research completed by Leah Domb through Harvard's bio-anthropology department and recently released in last week's issue of Nature magazine--the swelling during mating time actually serves to predict a female's fertility.

Baboons are one of the few ape species whose reproductive area swells during ovulation. Biologists used to view the swelling of the baboon

behind as just another example of a sexual trait evolved to attract

mates--similar to the decorative tales of male peacocks.

But Domb's research has demonstrated that the baboons' swelling is more than just decoration.

"Our study has shown that females are producing an honest signal of their

reproductive quality," Domb said.

The idea is that the bigger the bottom, the better the mom, according to the study released by Domb and her partner, Mark Pagel of the British University of Reading. The signal is then picked up by the male baboons.