There could be great variance in intelligence, physical strength and aggressiveness between different races of the same species. For example Chihuahua, Doberman and Gray Wolf are races of the same species (Canis Lupus).

Of course humans were not a subject to strictly controlled selective breading like dogs, which means we have much fewer and less diverse races. Still, this is not something that should be completely ignored when trying to understand human behavior, both social and genetic traits matter.