PreNeolithicMalaria · Evolutionary history of the sickle cell trait among Central African hunter-gatherers and farmers

Tertian malignant malaria (or malaria for short) currently kills more than 400k people per year in sub-Saharan Africa. Malaria probably became endemic in that region during the Neolithic transition, due to the spread of agriculture, thus imposing a strong selective pressure on the human genome. As a consequence, sickle cell anemia, a genetic disease that protects against malaria, is thought to have been selected and maintained at high frequencies among sub-Saharan farmers (Bantus) by balancing selection since the Neolithic. However, recent observations provide grounds for challenging this predominant view. Indeed, the high incidence of the sickle cell trait in sub-Saharan hunter-gatherers (Pygmies) and a pre-Neolithic origin of the human malaria parasite suggest that malaria infections affected humans much earlier than the Neolithic. Using genetic data from a cohort of Bantu and Pygmy populations, I will here test the alternative hypothesis that the sickle cell trait was selected and spread among African hunter-gatherers before the Neolithic. If proved correct, this hypothesis would indicate that human genomic resistance to parasitemias exacerbated by the spread of agriculture could have facilitated the Neolithic transition, rather than being its consequence. This new knowledge would allow us to re-evaluate the long-term role played by genetic adaptation to malaria in human evolution and to put into a new perspective a classical case study of gene-culture co-evolution.