I'm dubious of any moral claim, such as valuing vegetarianism or celibacy, that requires people to act contrary to their natures in a way that decreases their fitness.

Genetic fitness matters, because a moral system must be evolutionarily stable.

This implies that tragedies of the commons are acceptable under such moral system.

(Under the "tragedy of the commons" I mean a situation where "selfish" members of a population take advantage of a communally-maintained resource while not contributing to it, thus gaining free energy to outreproduce the "good citizens", thereby increasing the frequency of the genes for cheating and reducing the frequency of the genes for maintenance of the common resource. Any population consisting only of "good citizens" is evolutionarily unstable because it is vulnerable to an invasion of "selfish" mutations.)