Thermoregulation

The development of homeothermy - the maintenance of a constant body temperature - was one of the most significant steps in life's independence from the surrounding environment. Several groups of vertebrates, notably dinosaurs and birds, have acquired it, but it is in mammals that it is undoubtedly the most complete. At the base of the brain, the hypothalamus is a veritable temperature control center, capable of triggering effective reactions in the body to combat excessive heating or cooling. The ability to perspire, greatly facilitated by the loss of body hair, is highly developed in humans, no doubt in relation to their adaptation to endurance running. The phylogeny of hair parasites enables us to retrace the chronology of evolutions that led from the loss of fur to the development of clothing in hominins. Changes in the ratio between body mass and surface area represent an important means of adapting to different climatic environments. And in humans, as in other mammals, there are significant variations in body proportions depending on the environment. During the Pleistocene, these proportions also varied from one group to another according to climatic constraints. The development of brown fat, rich in mitochondria, is one of these adaptations, helping to combat the risk of hypothermia in newborn humans. In the late Paleolithic, the ability to build dwellings and make complex clothing played a key role in the colonization of peri-arctic environments by modern Homo sapiens.