Till death do us part
Malaria, the great killer, is carried by the mosquito, Plasmodium falciparum. It is found throughout the tropics but, while much is known of the biology of this insect, relatively little is known about its genetic diversity. Tanabe and colleagues examined 519 isolates from around the world and sequenced two housekeeping genes, identifying a series of single nucleotide polymorphisms (SNPs). Interestingly, the diversity of various geographical populations of P. falciparum almost exactly matches that of humans indigenous to that locale. In both cases, this corresponds to a decrease in diversity as the region analysed moves further from sub-Saharan Africa. This strongly supports the notion of a joint origin between P. falciparum and our own species and a co-evolutionary relationship with this parasite for most of our existence.
Tanabe, K. et al. (2010), 'Plasmodium falciparum accompanied the human expansion out of Africa', Curr. Biol. Vol. 20, pp. 1283-1289.