  One worry is that what best increases reproductive fitness is acting as a kin altruist rather than as a rational egoist (Crisp 2012, Other Internet Resources).  Presumably, then, it is believing that I ought to act as a kin altruist, rather than as a rational egoist, that best increases my reproductive fitness.  (If there is a tie between what increases reproductive fitness and belief, and believing that rational egoism is true is best for reproductive fitness, one would expect many to believe that rational egoism is true.  But very few do, while many endorse Broad’s “self-referential altruism” (Broad 1971b).)  De Lazari-Radek and Singer reply that the recommendations of rational egoism are very close to those of kin altruism, and much closer to those of kin altruism than are the recommendations of utilitarianism (2014 194). But rational egoism and kin altruism do make opposed recommendations. For example, kin altruism might recommend that I sacrifice myself for my family, whether I care about them or not, whereas rational egoism would recommend sacrifice only if my welfare were to be higher were I to sacrifice and die rather than not sacrifice and live. It is also hard to think of a plausible argument which has kin altruism as a premiss and rational egoism as the conclusion, so doubts about kin altruism do not seem to undercut arguments for rational egoism.  Nor is it clear how noting a difference in the closeness of recommendations justifies concluding that rational egoism is debunked and utilitarianism not debunked.