Many Asian people have perfect pitch because pitch can determine meaning in their language.

In tonal languages, it isn't absolute pitch that determines meaning - if that was the case, people with bass and soprano voices would have no shared vocabulary. So perfect pitch is irrelevant.

This has been investigated with speakers of the tonal languages of Africa, and it seemed that perfect pitch mainly correlated with being brought up from infancy in a quiet environment, like a rural village.

I don't know where Don's stuff about Pythagoras comes from, but it's urban legend. The ancient Greeks never had scales with 12 pitches, and neither did mediaeval musicians who used "Pythagorean" tuning.