The Minnesota Transracial Adoption Study proved that intelligence is in fact inherited and something like around 60% of someone's intelligence is inherited from their parents, while the rest is environmental. They did a study on black children adopted by white middle class parents and at 17 they were all given the Stanford–Binet IQ test. The results were that the average IQ of the black children was 89, just 4 points away from the whole black average of the United States. The study also included white children adopted into white middle class families and the average was 106. The type of communities blacks create and live in not only in the United States, but around the world is because that is what low IQ populations create. If they are still not convinced, tell them the physical differences such as skull size and brain capacity. For skull structure you can easily distinguish African, European, and Asian skulls from one another by just looking at them side by side and you can even show them a picture. A review of the world literature on brain size and IQ by Rushton [Rushton, J. P. (1995). Race, evolution, and behavior: a life history perspective. New Brunswick, NJ: Transaction] found that African-descended people (Blacks) average cranial capacities of 1267 cm3, European-descended people (Whites) 1347 cm3, and East Asian-descended people (East Asians) 1364 cm3.

https://en.wikipedia.org/wiki/Minnesota_Transracial_Adoption_Study

http://www.sciencedirect.com/science/article/pii/S016028960200137X