Pregnant—and Still Macho Male seahorses allow scientists to test extreme notions of sex-role reversal

One-half of the human race may find the idea more interesting than the other half does, but regardless, there's been plenty of speculation on what the world would be like if males were the ones who got pregnant. The more elaborate hypotheses— about warp-speed progress in obstetrics or Tiger Woods endorsing maternity clothes—have yet to receive rigorous testing. However, some of the basic theories of sexual behavior and sexual selection are getting attention thanks to a burst of new studies in the topsy-turvy social world of the seahorse.