Humans have always lived for others but the question was about determining the boundary. My Family, My Extended Family, My Clan, My Language, My Culture, My Race, My Humans, My Animal Kingdom, My Living Kingdom, My Earth, My Solar system, My Galaxy, My Universe etc.
It's part of the cultural evolution of the Humans.
There was time when we had cannibals who had their boundaries between their clan and race. Hence it was okay for them to eat humans from other clans/races.
Most of the world today is some where between my race and my Earth
Currently my boundaries are set some where between My Animal Kingdom and My Earth. Hence I am a vegetarian and an environmentalist.