[ingenium]

Your comment that forced hereditary occupations lead to differences in IQ. I fail to see the selecting force that would drive a lower IQ. If there are generations of manual labor as an occupation, that would be a selection force in favor of being stronger and bigger, but would not select AGAINST intelligence.

Other than that, there are clear differences in race genetically. Caste, in the Indian sense, is much harder to argue and would have to say the differences are minimal since it is more recent on an evolutionary timescale. Exceptions are when there was forced selection, such as with the slave trade which lead to the descendants of slaves being larger and stronger than those still in Africa. If there is a physical difference in appearance, then there is a high probability of other genetic differences. A perfect example is the distribution of immunity to HIV. It's really only in Europe, specifically Northern and Eastern Europe. Different geographic areas have had different selecting forces over thousands of years, so the populations are different.