during the ice age the earth was much colder and the sun was less hot. the first humans who moved from Africa during the ice age were probably as white as the Europeans of today because of the cold climate. eventually, the ice melted and the temps near the equator got hotter, tanning the inhabitants of the area. by then of course, Asian migrants had already crossed the ice into the Americas and some had settled near the equator in south America.
science tells us how humans managed to populate so much of the earth during the ice age and why there were already humans in the Americas after the ice age.