The burden of bearing a massive penis

Maybe half of my audience here will be familiar with this problem. You're a man, and you're hauling this massive, ummm, package around in your pants everywhere you go. Other men fear you, while the women worship you…yet at the same time, your e-mail is stuffed to bursting with strange people making friendly offers to help you make it even bigger. It's a dilemma; you think you would be even more godlike if only it were larger, but could there possibly be any downside to it? (There is a bit of folk wisdom that inflating it drains all the blood from the brain, but this is clearly false. Men who are stupid when erect are also just as stupid when limp.)

A couple of recent studies in fish and spiders have shown that penis size is a matter of competing tradeoffs, and that these compromises have evolutionary consequences. Guys, trash that e-mail for penis enlargement services—they can make you less nimble in pursuit of the ladies, or worse, can get you killed.

Spiders don't have penises, actually; the analogous structures are modified mouthparts called pedipalps that the male charges up with sperm and inserts into the female's ventral opening to inseminate her. (More details on spider sex can be found in the article Spider Kama Sutra). The palps of male spiders have often evolved into quite intricate structures that are keyed to the details of the female's genital opening.

Many spiders exhibit sexual dimorphism as well, typically with the female much larger than the male. In spiders of the genus Tidarren, this trend is carried to an extreme, with males that may be 1% of the female's size. Here's a photo of one of these little guys clinging to his girlfriend's underside, copulating frantically (there is cause for hurry, since she might decide to eat him). While on the one hand the threat of cannibalism might be a reason to be inconspicuous and unnoticed, on the other the male needs to make species-specific displays in order to get so intimate with his mate, and needs pedipalps that she will recognize. Perhaps I'm anthropomorphizing overmuch, but there may also be personal reasons—who wants to be so tiny that the female doesn't even notice when you're mating?

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