Speculations on the origins of Plasmodium vivax malaria.

It is likely that Plasmodium vivax diverged approximately 2 million years ago from a group of malaria parasites which are now endemic in monkeys and apes in southern Asia. In those times, primates were spread throughout most of Eurasia and Africa, indicating an Old World location, but nothing more precise, for the place of divergence of P. vivax. From approximately 1 million years ago, the Ice Ages would have isolated human malaria, including P. vivax, into humid temperate or warm climate refuges around the Mediterranean, in sub-Saharan Africa and in south and east Asia. As there appears to be no record of humans in south and east Asia from 100,000 to 60,000 years ago, they might not have passed on their parasites, including P. vivax, to modern humans entering the region after this time. Today, all P. vivax might be descended from parasites which infected human populations in the Mediterranean region and in sub-Saharan Africa during the last Ice Age, between 100,000 and 20,000 years ago. Evidence for the latter is provided by the presence of very high frequency RBC Duffy negativity in sub-Saharan Africa.