If Adam and Eve were literal people, then all human beings would have come from them originally.
As to the origin of the races, there were waves of people that spread all over, some of them were more primitive than others. When newer waves came in, they might have mixed with some of the earlier waves that were already different in each region. Also people have paler skin where the sun isn't as strong to allow for more Vitamin D absorption, and darker skin in stronger sun to protect from skin cancer. Other features such as facial structure, brain size, etc. are also related to environment and the needs of survival.