Africa, parasites, intelligence To understand intelligence in the tropics, e.g. among dark-skinned Africans, you need to understand the importance of parasites—both as an environmental factor that exerts a negative effect on mental development and a positive effect on selection for biological diversity of all sorts, including intelligence. 1. Taking first the well-known negative effect of parasite load on individual intelligence—in the US the parallel factor is toxins and also indoor parasites, as in tenements—the US is now more segregated by race than it was in 1965 and so that many studies show that there is a strong tendency for whites to live in healthy environments and blacks inferior habitats. For Africa, the environmental factor is parasites—disease—known to exert a strong negative effect on intelligence. They also exert a very strong positive effect for genetic diversity in their hosts that may in turn select for some groups excelling in intelligence, even if the mean is lower—variance is higher. 2--Hominids have always emerged from Africa, erectus, sapiens, sapiens neanderthalensis and sapiens sapiens, but with trivial exceptions never in the reverse direction--why? Because Africa is the most genetically variable part of the world, especially the smaller the organism, hence parasites. African human populations are invariably more genetically variable than more temperate hominids, including today. The same rule applies more generally, that is, to almost all species—migration is always tropics to temperate to arctic, rarely the other way around (e.g. salamanders are the exception: temperate to tropics)—it is Mexicans and people further south who are coming into the US, not Canadians and Eskimos. So Trump is erecting a barrier against Darlington’s Rule—migration is always tropics outward. Africa is the center of the tropics in the entire globe. Before that it was part of Gondwanaland (Africa, South America, Antarctic) but it was the center of th