Physiological polytypism is affected by a variety of environmental and genetic factors, and physiological parameters have been observed to vary between different populations and even within population in different environments. In particular, adaptation to cold environments is considered to have played an important role in the survival of Homo sapiens during the last glacial period, and recent studies have suggested that non-shivering thermogenesis in humans played an important role in our recent evolutionary history. This review examined human physiological adaptations to cold, specially the importance of physiological polytypism in non-shivering thermogenesis in humans.
