system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If natural selection is based on survival of the fittest, why do most people instinctively and passionately protect the weak? Why is it almost universally considered unethical to kill (or let die) less "fit" people?

Edit: I strongly believe the weak and "unfit" should be protected, I just don't understand why that is such a pervasive and powerful instinct when the basis for our evolution is essentially refining the gene pool by letting weaker members die off.
gpt
Fit also means being able to operate in groups. Humans who have group instincts will alway beat humans whose instinct is to be alone, no matter how fit they are individually. Part of the group instinct is fairness and to protect fellow members.

So we don't always protect the weak (or else there wouldn't be a homeless problem), but we have urges to protect everyone that is part of our group.