Fire in the Plio-Pleistocene: the functions of hominin fire use, and the mechanistic, developmental and evolutionary consequences.

Fire is a powerful natural force that can change landscapes extremely quickly. Hominins have harnessed this resource for their own purposes, with mechanistic and developmental physiological consequences. In addition, the use of fire has niche constructive effects, altering selective environments for genetic and cultural evolution. We review the record for hominin fire use in the Plio-Pleistocene, before considering the various functions for its use, and the resultant mechanistic and developmental consequences. We also adopt the niche construction framework to consider how the use of fire can modify selective environments, and thus have evolutionary consequences at genetic and cultural levels. The light that fire produces may influence photoperiodicity and alter hormonally-controlled bodily rhythms. Fire used for cooking could have extended the range of foods hominins were able to consume, and reduced digestion costs. This may have contributed to the expansion of the hominin brain and facial anatomy, influenced by a higher quality cooked diet. Fire may also have allowed dispersal into northern areas with much cooler climates than the hominin African origin, posing novel problems that affected diet and social behaviour.