Without having read the entire thread, and without knowing too much about this; I've got one question: From a darwinistic evolutionary perspective, what reasons would there be for certain so-called "races" to become more intelligent than others?

I think none, really. I mean, it's obvious that different environments require different physical attributes - such as dark skin in warmer climates, and pale in colder - but it's not like surviving in for example a European climate requires higher intelligence than surviving in an African climate.