Don't worry, men: Evolution shows you're still needed

Science may have found an answer to that question made famous by Maureen Dowd: Are men necessary? If other creatures are anything to go by, men are essential to keeping our species healthy, and would still be necessary even if women started making their own sperm. That's more or less what happened to the male clam shrimp, a puddle and pond dweller that thrives in all continents except Antarctica.

One day millions of years ago a mutant female started producing both sperm and eggs; that mutation spread until all the females were replaced by hermaphrodites. You'd think that would spell doom for the males. Hermaphrodites also dominate one of our fellow vertebrates, a swamp dweller called a killifish. And yet male killifish crop up here and there. Are these males getting any sex or in any way contributing to the gene pool? Are they necessary? An even more serious question ...