The only time it pays to be stabbed repeatedly happens to be during sex

What if every time you had sex, you had to agree to let your partner stab you first — would it be worth the trade-off? While you're mulling that over, consider this: in some species of hermaphrodite sea slug, the trade-off is flipped, with some slugs enduring the unpleasantries of sex in the hope of getting a stab… » 8/26/12 1:00pm 8/26/12 1:00pm