In an article titled, "Why Women Aren't Funny" in this month's Vanity Fair, Christopher Hitchens writes, "The chief task in life that a man has to perform is that of impressing the opposite sex. . . . Women have no corresponding need to appeal to men in this way. They already appeal to men. . . ."

It doesn't quite ring true. Perhaps he's considering only beautiful women - effortlessly beautiful women.

Hitchens' visual system may not even be equipped to detect average-looking or frumpy women. But despite the insincerity, his argument brings up an interesting scientific question: Do males really have to work harder?

Yes, says Richard Bribiescas, a Yale anthropologist and author of the book Men, Evolutionary and Life History.

"The tendency to compete over females is not just universal across cultures but pretty universal across all mammalian species," he says.

That doesn't necessarily mean men are funnier - though Hitchens cites a Stanford study showing men respond to cartoons differently from women. But we do know men are more driven to do what Bribiescas calls "coalescing resources," whether they come in the form of cattle or sheep or yachts.

Such a striking sex difference probably stems from sexual selection - in which males and females compete with their own sex for access to the opposite sex.

Males generally produce many more sperm than females produce eggs. That means males are more likely than females to become evolutionary dead ends, but those that do procreate can potentially leave behind a surprising number of offspring.

In his book Sex Wars, biologist Michael Majerus lays out various reproduction records for female and male animals: In red deer, it's 14 for does to 24 for bucks. He cites the Guinness Book of World Records in reporting that the female reproduction record is 69 children. For men, it's 888 kids.

The male record is attributed to an Emperor of Morocco known as Moulay Ismail the Bloodthirsty.

Some male animals still show a curious lack of competitive drive. Darwin himself wondered why some creatures show almost no sex differences, says Don Levitan, a biologist from Florida State University.

Levitan studies sea urchins, a cousin of the starfish. Sea urchins come in many species and across the board males aren't any prettier than the females. They aren't any bigger, and they don't do any special courtship behaviors.

And sea urchins are not, as far as anyone can tell, funny.

How do they get away with it?

The key to the puzzle is in the way the sea urchins have sex, says Levitan. Biologists have a pretty broad definition of sex, so they consider sea urchins to be sexual creatures even though all they do is cast their sperm and eggs out into the water - a system called broadcast spawning.

That means they can delegate the burden of finding and competing for mates to their sperm and eggs.

In crowded urchin tide pools, the males make short-lived but fast sperm that compete by sprinting. But for more rare sea urchins, sperm have to live a long time and swim long distances to find eggs of their own species.

If humans engaged in broadcast spawning, men's sperm would have to be hilarious.

Broadcast spawning was probably an ancestral form of sex, says Levitan. Many other sea creatures, including a number of fish, do it this way. But then eventually animals started pairing up - swimming together as they released sperm and eggs.

And others started going all the way.

Copulation, says Levitan, probably evolved independently many times - in vertebrates, in different lines of insects, in squids and their kin. So no one really gets full credit for inventing it.

There's new evidence that human sperm are still evolved to compete thanks to a long evolutionary history of women mating with more than one man in the same couple of fertile days.

But sperm can only do so much of the hard work. A man's sperm won't get to the playing field unless he gets off the couch and advocates for them one way or another. It's the price the male of our species has to pay for not bearing children while enjoying a more intimate and interesting sex life than the sea urchin.

Contact staff writer Faye Flam at 215-854-4977 or