Patterns of colonisation and the "thrifty" genotype in Pacific prehistory

The seemingly distinctive markers of Polynesian biology - serologic, molecular, anatomical, and developmental - have been argued to have emerged from the special circumstances of colonisation and early settlement of the region. Models point to the microevolutionary impact of mortality selection while voyaging, small founding group size forcing bottlenecking, and subsequent relative isolation of groups introducing heterogeneity through genetic drift within Polynesia. These ideas have drawn on a melange of ideas about the colonising experience to construct evolutionary narratives, including that of the "thrifty" genotype in Polynesia. The substantial problem is that there previously has been no independent theory of colonisation and inter-island contact for the region. We critically examine which microevolutionary forces would have impacted prehistoric Polynesians in terms of an independent navigational theory of colonisation, and map out the expected biological/ evolutionary sequelae. This theory suggests that Remote Oceania was settled by directed return voyages, that the tempo of population expansion was probably rapid, that voyaging continued after settlement, that whereas episodes of colonisation were directed to safety, subsequent inter-group voyages followed the pattern of mutual inter-island accessibility. The implication is that mortality selection would not have been the predominant force shaping the Polynesian genotype; the development of survival sailing strategies were designed to remove these very risks. This makes it unlikely that the specific experience of Polynesian colonisation would promote an efficient insulin mechanism, and so explain, for example, the high incidence of Type II diabetes mellitus in contemporary Polynesian groups.