Human social institutions can effect the course of human evolution. Just as climate-change, food supply, predators, and other natural forces of selec… - Peter Singer

when we make ethical judgments, we must go beyond a personal or sectional point of view and take into account the interests of all those affected, unless we have sound ethical grounds for doing otherwise. (...) The essence of the principle of equal consideration of interests is that we give equal weight in our moral deliberations to the like interests of all those affected by our actions. (...) an interest is an interest, whoever's interest it may be.

We do not have to make self- sacrifice a necessary element of altruism. We can regard people as altruists because of the kind of interests they have rather than because they are sacrificing their interests.

the fact that no one has come up with a really convincing reason for giving greater moral weight to members of our own species, simply because they are members of our species, strongly suggests that there is no such reason. Like racism and sexism, speciesism is wrong.