How did Darwin's theory of evolution influence American thinking about race?

I know the answer but i don't rememmber it so sorry

Darwin saw sexual selection, in which basically trivial preferences shaped the appearances of populations over time, as a means by which races with a common origin could have acquired their visible differences.

Darwin thus emphasised human unity and dwelt upon superficial differences, while acquiescing in the contemporary assumption that some races were superior to others.

Explanation:

In his book The Descent of Man, he theorized that man, having evolved from apes, had continued evolving as various races, with some races more developed than others. Darwin classified his own white race as more advanced than those "lower organisms" such as pygmies, and he called different people groups "savage," "low," and "degraded."