In adult life we're a mixture of a disposition to help other people and a disposition to ignore or even harm them - and it seems to accord with experience to say that we start out with that kind of mixture.

How we balance out those is presumably affected by what happens to us along the way, and how the people around us act - but to assume that we're naturally sweet all the way down seems a bit too optimistic.

Midchuck's little pack animals ("GUEST 10:27) aren't the whole story, but they're a big element in it.