'Survival of the fittest' has been explained before.
It doesn't mean pushing others aside! A lot of animals work together, SO THEIR SPECIES CAN SURVIVE. Soldier or worker ants will die for their colony. Should each and every ant that lost his life be remembered as a martyr? I actually read a book once (by a French writer) about ants, that actually DID start their own religion at some point. But that's a bit besides the point.
Self-sacrifice may sound noble, but it happens all the time. For some species, reproducing actually MEANS dying! A certain type of californian squid dies after is has deposited its eggs-capsules and male spiders risk their life even before they have mated! (The females are in most species larger and have been known to eat the male, before, after or during copulation).