"Zeus gathered the gods in council to express concern that these unusual creatures would one day challenge their hegemony. He was loathe to exterminate them with his thunderbolts, though, because there would be no one to bring the gods offerings. He solved the problem by putting each creature into a trance and then splitting it down the middle...
...Upon awakening each half only dimly remembered what it had been prior to being cleft in two. Zeus explained to the assembled gods and goddesses the cleverness of his scheme. These creatures would no longer pose a threat to the gods,because they would dissipate their considerable energy by spending the rest of their days searching for their missing halves."