Some moral realists claim that moral facts are a species of natural fact, amenable to scientific investigation. They argue that these moral facts are needed in the best explanations of certain phenomena and that this is evidence that they are real. In this paper I present part of a biological account of the function of morality. The account allows the identification of a plausible natural kind that could play the explanatory role that a moral kind would play in naturalist realist theories. It is therefore a candidate for being the moral kind. I argue, however, that it will underdetermine the morally good, that is, identifying the kind is not sufficient to identify what is good. Hence this is not a natural moral kind. Its explanatory usefulness, however, means that we do not have to postulate any further (moral) facts to provide moral explanations. Hence there is no reason to believe that there are any natural moral kinds.