[tortoise]

What I'm getting at is that such people have a strong sense of what is right that causes them to forego the (admittedly strong) self-preservation instinct that one would expect from evolutionary theory.

Evolution does not proscribe a self-preservation instinct. All it does is optimize the chances for the survival of the species. Obviously wholesale suicidal tendencies wouldn't generally be a strong survival trait for a species, but selective individual sacrifice to enable group survival would be. Self-preservation is the default behavior for animals, but this behavior is often overridden to optimize the mortality patterns for the benefit of the species. The pattern we generally see is self-preservation EXCEPT when self-preservation instinct would likely result in a greater net loss in survivability for the species.

[yendu bwam]

Here's an interesting thought: The vast, vast majority of the world's population is involved in organized religion. This could be explained, I'll admit, by a number of things. But in virtually every one of those religions, adherents are taught to be self-sacrificing - in Christianity (the world's largest religion), people are taught to give up material wealth, to sacrifice for the good of strangers (the good Samaritan), to love those who hate us, to resist urges for premarital sex and adultery, to humble ourselves, to turn the other cheek, etc. etc. More people believe this or want to be part of this movement than any other on Earth. Yet every one of the things mentioned above, weakens the individual's (or the species') chances for survival. Amazing, isn't it?