Any studies, science, or statistics that show differences between the races are immediately classified as biased, racist, and flat-out untrue and are thrown away. It's a travesty that legitimate facts are ignored by scientific community and society at large because they're not "nice". How much potential knowledge in the areas of medicine, psychology, and sociology have we sacrificed for political correctness because we flat out REFUSE to acknowledge human difference and condemn, indeed socially damn, those who dare to bring it up.

Nature doesn't take 'niceness' into account when adaptation and evolution is taking place. All it cares about is survival and the passing on of genes to the next generation. Adaptations that are beneficial get passed on and eventually integrated into the species if they're essential. Those adaptations that aren't beneficial, or aren't essential for that particular environment, aren't passed on.

The races of the world evolved in very different environments, even while assuming we all share the same origin. Northern peoples, like those who grew up in Europe, evolved in very cold environments where shelter and the ability necessary to plan ahead and sacrifice today so you could save food for the winter was needed. Those who didn't have that ability died off. Those in Africa during the same period didn't experience the challenges of winter the Europeans did, but instead were subject to different sets of challenges that required wholly different adaptations. Those in Asia experienced their own unique challenges.

Different challenges lead to different evolutionary traits, which leads to different strengths and weaknesses. That doesn't mean any race is superior to any other, but it does mean we are indeed different. There's nothing wrong with that, though. Those who say they celebrate diversity seem to actually be afraid of it and unable to admit its existence.