Yeah but that's because ability to roll down is directly caused by the observable geometry. They are just different properties of the same trait. Skin tone or facial structure cannot cause someone to be intelligent. If you flattened the sides of the round balls, they'd be just as slow. But imagine there's some new way to painlessly crush people's faces into different racial-typical shapes and change the color of their skin to some racial-typical tone. Would this cause their intelligence to change? Obviously not. So how is this different than people with different physical characteristics from birth?
Race categorizations are made by humans according to how people look. From wikipedia's definition "Race, as a social construct, is a group of people who share similar and distinct physical characteristics." You're saying that these physical characteristics somehow also indicate how people behave (outside of social conditioning). There is really no reason to conclude that.
I think this wiki section on race along with the sources mentioned are useful here.
>There is a wide consensus that the racial categories that are common in everyday usage are socially constructed, and that racial groups cannot be biologically defined.[22][23][24][25][26][27] Nonetheless, some scholars argue that racial categories obviously correlate with biological traits (e.g. phenotype) to some degree, and that certain genetic markers have varying frequencies among human populations, some of which correspond more or less to traditional racial groupings. For this reason, there is no current consensus about whether racial categories can be considered to have significance for understanding human genetic variation.
https://en.wikipedia.org/wiki/Race_(human_categorization)#Co...