Malarial Climes

The tropical rainforest is the ecologically richest enviroment on Earth. There are (or were) up to ten times as many species per unit area in tropical rainforests as in temperate regions. These tropical rainforests have been rapidly vanishing for the past half century or so, and are likely to be essentially gone in a couple more decades.

Despite their species diversity, the TR's have usually not supported large human populations - not enough humans to destroy their relatively fragile ecologies. They largely resisted the onslaught of European civilization until relatively recently. There is a common factor between those facts: Malaria. Malaria and other tropical diseases (yellow fever, tsetse flies, etc.) have protected the jungle for millenia.

Populations living in malarial climes have evolved some expensive defenses, most notably, sickle cell anemia. Persons having two sickle cell genes typically die very young of sickle cell disease. Heterozygotic individuals have better chances of surviving both. The cost of this adaptation is losing 1/2 of your children up front, plus the cost of the possibility of sickles cell disease among the heterozygotic, plus the cost of malaria.

Modern insecticides, other prevention programs, and treatment have greatly reduced the effect of malaria, but has had the undesireable side effect of making it easier to destroy the tropical rainforests.

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