Or, another way of looking at it, a particular environment favors the survival of particular genes, and disfavors others, such that over a hundred generations, particular traits are significantly selected for.
Yep. That’s why Caucasians vary from snow white blond and blue in areas will little sunlight in northern Europe to as dark as any African in sunny southern India.
Drop a colony of Swedes in south India and they’d be so badly adapted that they couldn’t survive generationally, so many would die young of skin cancers that there wouldn’t be enough elders to pass on wealth and wisdom.
Swap a family of southern Indians with the swedes in Sweden and (unless the figured out the secret of eating seal liver) they’d suffer from vitamin-D deficiency and rickets.
Caucasians all, just adapted to local conditions.