Evolution builds from bottom up. There was no grand design from the beginning. The primal instinct was self-preservation, which is obvious, because otherwise, no one will be sitting here. But then with time, self-preservation required mutual collaboration between primates, especially homo sapiens, because of the harsh realities they faced in Africa. So now evolution adds a new layer that contradicts the first one, which is the layer of hyper socialization and cooperation. So, I agree, human relationships are of mutual benefits for the individuals involved, even though, I think the equilibrium point at which all individuals benefit equally is very difficult to achieve, as selfishness, I believe, is still the stronger instinct.