Prophet
breaking the statutes of my local municipality
We'll use an example from grammar. In a sentence, there's always: subject-verb-object. Now apply this to morality. The subject, whether it be you, me, or whoever, the verb, which is the action done, and the main body of the morality, and the subject, which, in the case of morality, is almost always another person. If you act in an immoral way toward another person, the tribe/community is likely to reprimand you. Do it enough, and you get kicked out of the tribe, thereby signing your death warrant. Now, what are some immoral actions, generally considered? Things like envy, jealousy, battery, theft, murder, adultery. Instead of prescribing an equal moral to each one, they can all be summed up as: love. Generally, selfless love. So no, sacrificial love, as you put it, does not have to come from a higher source, but comes from evolution.
Measure morality with respect to action and you will confuse. Instead, measure morality with respect to motive. Action is amoral.