Final answer:
Human racial differences are not the result of separate evolution, but rather recent evolution and adaptation since Homo sapiens originated in Africa around 200,000 years ago according to the "Out of Africa" model.
Step-by-step explanation:
Human Evolution and Racial Differences
Modern humans, or Homo sapiens, evolved in Africa around 200,000 years ago and later migrated to different parts of the world. The "Out of Africa" model supports this view, suggesting all humans have a common ancestor from Africa, and this theory is widely accepted due to genetic evidence such as mtDNA studies. However, the multiregional evolution model proposes simultaneous evolution from Homo erectus in different regions. This is less supported due to less genetic backing compared to the fossil record. Anthropologists and geneticists generally agree that the idea of race from a biological standpoint is not valid, as human variation is continuous with only a small number of genetic markers influencing physical traits often associated with race, such as skin color.
Overall, racial differences are not due to separate evolution but rather recent evolution and adaptation based on migration and environmental factors. The current scientific consensus indicates a recent common ancestry, and thus, the varieties of human traits we see today have evolved over a relatively short period in human history rather than through separate evolutionary paths.