New Evidence for a Late Introduction of Malaria into the New World [and Comments and Reply]

New evidence is offered to strengthen the case for a post-Conquest introduction of malaria into the New World. An investigation of human physiological factors influencing host selection by malaria vectors revealed a strong preference by Anopheles gambiae for human hosts with blood-group O. The unique, overwhelming group-O frequency present among indigenous American populations is seen as a result of mother-child ABO incompatibility effects operating in the absence of the positive selection pressures by malaria vectors favoring enhanced survival for genes A and B that the investigation findings suggest. It is proposed that had malaria been present to act upon the original gene pool, a balanced ABO polymorphism would be found in the New World Indians today.