Cold case: Cold induced vasodilation response, and the origins of Polynesian body morphology as an adaptation to a cold environment

Abstract

The origins of Polynesian body morphology have been a source of speculation since early European explorers marvelled at their large physique. Climate is considered the major evolutionary factor behind body morphology. Bergmann’s and Allen’s Rules suggest that Polynesians exhibit a cold adapted body form, despite inhabiting a tropical environment. However, Polynesians have only inhabited the Pacific region for several thousand years; their origins lie in Asia. Past research has suggested this cold adapted body form evolved as a response to voyaging in the cold Pacific maritime environment. The emergence of Lapita culture in Near Oceania around 4,000 years ago, and its subsequent expansion by the ancestors of modern Polynesians across the Pacific in less than 3,000 years, does not provide the necessary time frame to evolve cold adapted body morphology. If Polynesians have cold adapted characteristics, their origins must lie in the high latitudes. This research examined the variation in human body morphology and resistance to cold, and its relationship to biogeographical ancestry. A total of 286 participants from Polynesian, Melanesian, European, Asian, Indian, and African ethnic groups were measured for body size and shape, and tested for their cold induced vasodilation response. Three questions were examined. To what extent does body morphology, specifically body size and body shape, represent adaptations to ancestral climate? To what extent does cold induced vasodilation response represent an adaptation to an ancestral climate? In the light of these results what are the likely ancestral origins of Polynesian body morphology? The results clearly indicate the cold adapted body morphology, and strong resistance to cold as displayed by cold induced vasodilation response, found in Polynesian populations when compared with other populations from both cold and tropical environments. This adds weight to the hypothesis that Polynesian ancestral origins lie in the cold climate of Northeast Asia many thousands of years ago. A robust physique may have been a significant advantage for early Oceanic explorers in their canoes, contributing to the success of their colonization of the Pacific. These origins may also be a factor in the high rates of obesity and diabetes found in modern Polynesian populations.