 This is supported in the variability selection hypothesis proposed by Richard Potts, which says that human adaptability came from environmental change over the long term.Bergmann’s rule states that endothermic animal subspecies living in colder climates have larger bodies than that of the subspecies living in warmer climates.Individuals with larger bodies are better suited for colder climates because larger bodies produce more heat due to having more cells, and have a smaller surface area to volume ratio compared to smaller individuals, which reduces heat loss.