Among our closest living relatives — the great apes — we humans are unique: We have larger brains, reproduce more quickly and have longer life spans. These traits are obviously valuable, but the extra energy required to sustain them is quite significant. So how did we manage to afford them?
A group of anthropologists from UC Santa Barbara, the University of Utah and Duke University have teamed up on a research study to understand the strategies humans developed for obtaining that extra energy. Their findings are published in the current issue of Science.
Evolutionary success is largely determined by the extent to which an organism is effective at extracting energy (i.e. calories) from the environment and converting that energy into offspring. But energy acquisition is constrained by a number of factors, the primary being how much time and energy one can spend in the pursuit of food. Energy budgets represent the balance between energy intake and expenditure that all organisms must navigate in order to survive and reproduce.
«Because energy is such a fundamental currency, evolution has produced many astonishing energy-saving adaptations across the Tree of Life,» said Thomas Kraft, the paper’s lead author. Currently an assistant professor at the University of Utah, Kraft conducted the research while a postdoctoral student with Michael Gurven, senior author and professor of anthropology at UC Santa Barbara. «But that doesn’t mean natural selection always favors reduced energy expenditure. In fact, tremendous variation exists in the ‘tempo’ of energetic strategies. A dramatic example is the difference between endothermic (warm-blooded) and ectothermic (cold-blooded) animals. Warm-blooded animals tend to use a lot more energy each day but are able to successfully channel that energy into activities that ultimately lead to successful reproduction.»
The researchers began by comparing the amount of energy and time humans and other great apes expend in order to obtain all the foods they typically include in their diets. «We studied contemporary subsistence societies of hunter-gatherers and farmers in order to examine the kinds of energetic strategies that have existed for millennia, including those after the advent of plant domestication,» said Kraft.
The team of scientists drew especially upon their long-term collective experience working with the Hadza, an indigenous group of foragers in northwest Tanzania, and the Tsimane, an indigenous group of horticulturalists in the Bolivian Amazon.
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Materials provided by University of California — Santa Barbara. Original written by Andrea Estrada. Note: Content may be edited for style and length.