The Geography of Race It is hard to ignore the fact that the different proposed races of the human species have originated in separate isolated regions of the earth. And where crossroads have been formed between these regions a blend of the races has developed. Physical barriers such as mountain ranges, oceans, desert regions, etc. 2. The effect of geography on climate which leads to the variations within species. Of less impact are the chemical or mineral variations in terrain and soil.
Physical barriers keep interbreeding between different regions to a minimum.
They restrict the movement of genes from spreading to other populations. In prehistoric times, the ability of human kind to break these geographical barriers was small. These factors in racial variations had a direct impact on the next two. Climate has a direct effect on the pigmentation of races. In areas where peoples were exposed to more direct sunlight, skin pigmentation becomes increasingly darker.