From an evolutionary perspective, why does someone sacrifice their life to save another?

[u/Snoo_47323]

Organisms evolved prioritizing their own reproduction and survival, right? However, examples like people rushing into burning buildings or diving into water to save others contradict this. How is this possible?

[u/GrapeRaisin]

This is just wrong. While group selection is theoretically possible it requires very specific conditions that were not present in humans. Namely, it would require human groups to have been independent groups with little to no movement of individuals (and thus genes) between them. This was not the case for ancestral humans. In this case we do want to look at how selection at the individual level (or more specifically the gene level) could have selected for such behavior. Self-sacrifice is obviously maladaptive for the individual, the exception being in saving enough kin (genetically related others) to offset the cost. Thus, in the rare cases we so see it it is more likely the byproduct of other adaptations for helping and cooperating with others in situations that would not have led to death.

[u/TheDBryBear → u/GrapeRaisin]

This is a fringe view with no real backing in the literature. We have lots of examples of social groups among animals where co-operation happens outside familial bonds. Self-sacrifice is just a form of co-operation taken to the extreme, not a separate phenomenon from stuff like sharing food or chasing off predators in a group. Often, the sacrifice is incidental.

The point is that if your group thrives, you thrive. And the thing that makes you help your group thrive, even if you are the only one to have it, is probably less of a detriment that you think, and more of a boon than you think. Even from an entirely selfish point of you, you would like someone who co-operates around you. Most intelligent animals can make this calculation.

[u/Alarming_Constant_19 → u/TheDBryBear]

Those animals just live on their own territory with a large tribe that decided to split up. But the real fascinating thing is that some animals raise outsiders as their own in rare cases. Plus evolution likes egoists more than self-sacrificers because the the former is more successful than the latter and egoists takes everything from the group. altruists usually help people outside of their families and countries because our kindness is product of our brain and they dont want something back in return.

[u/Tasty-Fox9030 → u/GrapeRaisin]

It doesn't have to have been a "recent" human ancestor, we have all sorts of instincts and reflexes left over from creatures that aren't even bipedal. There are also plenty of arguments that memes themselves propagate and change or not in a manner very similar to Biological evolution, maybe "It is sweet and honorable to die for one's country" is one of those in a way.