In evolutionary terms, we can easily understand altruism toward kin and others who can reciprocate our help. It seems plausible that once our ability to reason and reflect has developed sufficiently enough to enable us to understand that strangers can suffer and enjoy life just as we can, then at least some of us would act altruistically toward strangers, too.
为何我们要怀疑有人至少会有时采取利他行为？从进化论的角度，我们很容易就能理解对家人和可回馈帮助的人的利他主义。一个很有道理的说法是，如果我们推理和思考的能力足够发达，可以确保我们明白陌生人可以与我们一样受苦或享受生活，那么至少我们中一部分人也会对陌生人有利他行为。