James H. Brown, PH.D. and the New Mexico Human Macroecology Group in Nautilus:
Part of our energy budget is dedicated to biological metabolism, which is the set of processes through which our bodies produce and spend energy derived from the food we eat. This we share in common with all other animals. Unlike all other mammals, however, humans also use extra-biological energy, and a lot of it. The rate of biological energy use (or the metabolic rate) of a human is about 100 watts, equivalent to 2,000 kilocalories per day. But in the most developed countries, our average per capita energy use is on the order of 10,000 watts, or 100 times greater than what we need biologically. The total energy usage of an average person in the U.S., Canada, the Eurozone or Japan is equivalent to the biological metabolic rate of a hypothetical 30-ton primate. About 80 percent of this extra-biological energy consumption comes from burning fossil fuels.
In addition, unlike all other mammals, different communities of humans have vastly different energy consumption patterns. The New Mexico Human Macroecology Group has documented how energy use scales with GDP, a standard measure of economic activity. Across countries today, as per capita GDP increases by about 700 times, per capita energy use increases by about 200 times. This means that in the poorest developing nations of sub-Saharan Africa, the average per capita energy use is barely more than the 100 watts required for basic biological metabolism. Socially derived variations in energy consumption among other species do exist: for example, the alpha male in a wolf pack or a band of gorillas will often have a better diet and spend more energy. But these variations are rarely greater than a factor of two.
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