Malaria’s Eve: Evidence of a recent population bottleneck throughout the world populations of <i>Plasmodium falciparum</i>

<jats:p> We have analyzed DNA sequences from world-wide geographic strains of <jats:italic>Plasmodium falciparum</jats:italic> and found a complete absence of synonymous DNA polymorphism at 10 gene loci. We hypothesize that all extant world populations of the parasite have recently derived (within several thousand years) from a single ancestral strain. The upper limit of the 95% confidence interval for the time when this most recent common ancestor lived is between 24,500 and 57,500 years ago (depending on different estimates of the nucleotide substitution rate); the actual time is likely to be much more recent. The recent origin of the <jats:italic>P. falciparum</jats:italic> populations could have resulted from either a demographic sweep ( <jats:italic>P. falciparum</jats:italic> has only recently spread throughout the world from a small geographically confined population) or a selective sweep (one strain favored by natural selection has recently replaced all others). The selective sweep hypothesis requires that populations of <jats:italic>P. falciparum</jats:italic> be effectively clonal, despite the obligate sexual stage of the parasite life cycle. A demographic sweep that started several thousand years ago is consistent with worldwide climatic changes ensuing the last glaciation, increased anthropophilia of the mosquito vectors, and the spread of agriculture. <jats:italic>P. falciparum</jats:italic> may have rapidly spread from its African tropical origins to the tropical and subtropical regions of the world only within the last 6,000 years. The recent origin of the world-wide <jats:italic>P. falciparum</jats:italic> populations may account for its virulence, as the most malignant of human malarial parasites. </jats:p>