not race, culture
I do not know but I believe that tscience knows of no genetic differences between humans today yjay would make some folks stagnate. I think that any "stagnation" is a local effect of a tribe's isolation from the major civilizations.
Although I do not believe in inherent genetic differences significantly limiting humans success I do believe that cultural differences either enable or inhibit the ability of individuals to succeed. Some cultures are very effective - Jewish culture and American middle class culture for example. Others are sick and inhibit human success, Islamist culture for example. In the US I believe that urban African-American culture is disfunctional and seriously inhibits the success of black males in particular.