Vladimir Nesov:

"Only few responses to changing context are the right ones"

As long as they are "few" instead of "one" - and these "few" still means basically infinite subset of larger infinite set, differences will accumulate over time, leading to different personality.

Note that such personality might not diverge from the basic goal. But it will inevitable start to 'disagree' about choosing one of those "few" good choices because of different learning experience.

This, BTW, is the reason why despite what Tooby & Cosmides says, we have highly diverse ecosystem with very large number of species.