Evolutionary trade-off between weapons and testes.

Photo: flickr/Udo Schmidt Fast cars. Big boats. Massive weapons. Genital size. Totally uncorrelated? Not if you believe pop psychology, or if you are a scarab beetle. Although beetles don't drive or shoot guns, they often have huge horns that serve as weapons. But one could imagine that the energy used to grow these horns results in smaller genitals, and that's the hypothesis these scientists decided to test. Turns out, if you prevent a beetle from growing horns, it grows larger testes. This sounds like the basis for a new internet scam. Any takers?Evolutionary trade-off between weapons and testes. "It has long been recognized that male mating competition is responsible for the evolution of weaponry for mate acquisition. However, when females mate with more than one male, competition between males can continue after mating in the form of sperm competition. Theory predicts that males should increase their investment in sperm production ...