I just wanted to add a sidebar/support here. This Stanford study about how the "voices" associated with schizophrenia vary widely according to culture suggests that culture (and of course family) have a profound effect upon the expression of any trait; perhaps to the extent of forcing something that becomes a clinical disorder.

For instance, the leader/follower ratio. You can even assume perfect rationality on the part of all actors; even with that assumption, nobody can rationally act outside of what their context will permit. That context is culturally enforced; suppressing or limiting the expression of various sorts of personality and intelligence. So a person who could be a leader still requires a context that will permit that. Family support, access to education, etc. This is also true of becoming an effective "sidekick," or any other set of traits.

And obviously, while context is required to effectively express a trait, no context will help if it's a trait you don't have in the first place.

But it's simple to point to various traits - Sexual and gender issues, the hearing of voices, asperger's autism, multiple personality and dissociation - that different cultures react to and deal with in wildly different ways, causing very different expressions. It seems unlikely that various forms of intelligence and degrees of competitiveness/assertiveness would be immune to this.