Cold adaptation as a life style strategy

Humans evolved in Africa, where climate would have required cold adaptation. Modern humans have housing which separates them from the environment. Metabolic disorders are prevalent in populations with excess Western diet and lack of exercise. A thrifty genotype has been proposed as an explanation for susceptibility. An alternative explanation is that cold adaptation is absent. But the human genome is complex, and there are many variations possible in the metabolic pathways. Behaviour which uses the circadian rhythms of metabolism may be helpful for fitness.