Altruism

I think we've had this discussion before ... do we believe that natural selection could ever really produce the traits of unselfishness, caring and sacrifice? I've heard various theories about the survival of the pack, but I don't buy it. For one thing, I'm unaware of any animal social construct where mating is done communally. They may act for the preservation of the pack when threatened by intruders, but propagation within the pack will go to the aggressive and selfish.