The evolution of human fatness and susceptibility to obesity: an ethological approach. Adaptation to a variety of local niches favouring population-specific adaptations. The development of social hierarchies which predispose to differential exposure to environmental pressures: thus, humans have persistently encountered greater energy stress. The capacity to accumulate fat has therefore been a major adaptive feature of our species, but is now increasingly maladaptive in the modern environment. Alterations to the obesogenic environment are predicted to play a key role in reducing the prevalence of obesity. Mammalian body mass can be divided into fat and fat free components. Life-history theory: considers how factors such as size and growth rate contribute to variability in the pace" of life and reproductive schedule of organisms. There"s difficulty of adopting evolutionary approaches to the phenomena of obesity that are not directly preserved in the fossil record. Humans have been described as being among the fattest of all mammals.