>>3792486 (OP)darker people are from hotter envioernments while paler people are from cold envioernments
Hotter climates have lesser evolutionary pressure for IQ and other abilities compared to colder climates.
Some brown in a hot climate can have trillions of children, live off of the forever hot fields growing food
To contrast in a cold climate, for half the year winter stops plants growing so theres great resource and food scarcity which creates evolutionary pressure for problem solving and long term planning leading to cold climate people generally having higher iq than hot climate people
Though there are expections to this general rule like ramanujan