Race is the same as subspecies. Each race of human is a subspecies of human. Subspecies is defined as where it has evolved in its own separate environment and by adapting to that environment, it has developed its own separate morphological and behavioral characteristics, even though it is still part of the species and thus still able to cross-breed with other sub-species from the same species. (Even though that has negative consequences to the offspring). There are emotional differences, intelligence differences, hormonal differences, physical differences, etc. There are medicines that only work for one race or another, etc.