Sex and the single monkey
Darwin's theory of sexual selection is under attack… What worries the minority of scientists who are openly challenging sexual-selection theory is that it is unable to account for much of the diversity of sexual behaviour that exists. If, for example, as sexual-selection theory assumes, mating is primarily about sperm transfer, why do some animals mate between a hundred and a thousand times more often than is needed for conception alone?
Because sex is fun! Natural (and Sexual) Selection are fantastic at explaining many adaptations, but not everything has to be an adaptation.