Malaria is one of mankind’s biggest killers, with an annual death toll in the region of 1.5 million. It has also been implicated in the prevalence of sickle-cell anaemia amongst blacks, and now also in the prevalence of alcoholism, again in blacks. Why blacks? Because Sub-Saharan Africa is plagued with malaria, and evolutionary adaptations to combat malaria have unintended side-effects.

From: The Loom

alaria wreaks colossal damage in many parts of the world. Today it kills over a million people a year, mostly children, and it has been plaguing our species for thousands of years. Carrying a single copy of the sickle-cell gene boosts the odds that people can have children in malaria-prone regions. Unfortunately, when two people who carry the gene have children together, there’s a one-in-four chance that each child will get both copies of the gene. Over many generations, the advantage of having one copy of the gene outweighs the disadvantage of having two—at least in populations that have endured centuries of malaria.

In the decades since the discovery of the sickle-cell trade-off, scientists have discovered that several other defenses to malaria have evolved where the disease is a high risk—in Africa, the Mediterranean, Southeast Asia, and New Guinea. And many of these adaptations come with drawbacks of their own. Now a new study offers evidence of yet another mixed blessing: one defense against malaria may make people prone to alcoholism.