Uniquely human subsistence strategies may have facilitated social and cultural development

Humans afford the high energetic costs of human life not through energy-saving adaptations – such as bipedalism or sophisticated tool use, both of which decrease the energy required to obtain food – but by acquiring energy at a far greater rate than our closest evolutionary great ape cousins. The findings illustrate that humans are not cost “economizers,” but rather are evolved to operate as high-throughput organisms that expend large quantities of energy in order to acquire energy at exceptionally rapid rates; this may have afforded our species free time for social and cultural development. Uniquely human traits – our big brains, and long developmental periods and lifespans – impose extraordinarily high energetic costs compared to other great apes. However, how unique human subsistence strategies accommodate such an expanded energy budget and the extent to which they reduce the energy and/or time costs of subsistence compared to other great apes remains unknown. Furthermore, direct comparisons between species are lacking. Thomas Kraft and colleagues evaluated energy intake and expenditure in modern hunter-gatherer and horticulturalist societies (the Hadza of Tanzania and the Tsimane of Bolivia) and other great apes. Kraft et al. found that, while humans spend more energy on foraging and farming, we acquire more energy and at a faster rate than great apes. The findings suggest that energy gained from improvements to efficiency in human evolution were primarily channeled toward further ramping up food acquisition rather than making food easier to obtain. According to the authors, this strategy could only be compatible with a highly cooperative and social species such as our own and may have helped facilitate the development of these traits in our species.