Energy constraints represent a major challenge for the adaptation of organisms, which must extract energy from their environment in sufficient quantities, in the form of food for animals. This energy must then be allocated to the various vital functions. The cost of these functions varies according to the organs involved, and from one species to another. Food acquisition and digestion themselves represent a significant energy cost. Among primates, humans have a very large brain, and this organ is particularly energy-intensive. In fact, many human traits are the result of adaptive adjustments that have enabled the evolution of an ever larger, more complex and more energy-consuming brain. The effects of these adaptations are most spectacular during growth. In particular, they have forced hominins to radically modify their diet in the lineage of the Homo genus.
Many other aspects of human life and activity can also be examined from an energetic point of view. Such is the case of bipedal locomotion, considered to be the founding characteristic of hominins, the tribe of species to which we belong. Like other mammals, humans have a constant internal temperature. The diversity of climatic adaptations that accompanied the colonization of our planet byHomo sapiens led to the development of cooling and heat conservation mechanisms, more or less active depending on the thermal environment encountered. In the end, however, it is above all man's ability to modify his environment on different scales that has made possible the adaptive success of our species in geographical areas with sometimes extreme climatic conditions.