And here is how Darwinism inspires scientists to suppress data about same sex behaviour (a rampant problem)" Intellectual worries run even deeper, perhaps. After all, homosexuality seems to be a clear non-starter from a Darwinian perspective. Why waste time in same-sex relationships when you could be making babies? Evolutionary theory measures success in the currency of genes: animals are supposed to be machines intent on spreading theirs around. "Researchers find male-male or female-female sexual interactions theoretically difficult to deal with," says Wolfe. "On the face of it, sociobiological theory says it can't happen. "No wonder then that putative gay sex among animals is typically explained away as examples of play, mistaken identity or an exercise in power. Indeed, some researchers, notably Tim Clutton-Brock of the University of Cambridge, would say that "true" homosexuality--if strictly defined as male anal penetration by males who show no interest in females--is virtually unknown among wild mammals. They argue that animals who mount same-sex partners and the like are behaving aggressively or merely practising for heterosexual encounters. Or they may be advertising their availability, or trying to make a heterosexual partner jealous.