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Sustainability Matters 2: Humans and Energy


Humans and Energy

For most of human existence, energy has meant food obtained by hunting or gathering.

The ability to conduct these activities was aided by a large brain, an opposable thumb, the development of language, and the use of stone tools.  We know Australopithecus afarensis or Kenyanthropus platyops, our hominin ancestors, used stone tools some 3.3 million years ago, or about 700,000 years before modern humans evolved with that skill.   We existed by using our own energy, ingenuity, and memory.  Language allowed complex communication and the development of a collective societal memory.

Energy was (and still remains) the key to our existence. 

Finding enough food to survive by hunting and avoiding becoming another predator’s dinner were the major activities of life.  The population was small and sparse.  Our effect on the environment was local and minimal.

One of the first significant human impacts on local environments was from our use of fire.

Humans first use of fire occurred more than a million years ago, but according to a recent paper, the emergence of habitual fire use began around 350,000 years ago.

     “Frequencies of burnt flints from a 16-meters-deep sequence of archaeological deposits at Tabun Cave, Israel, together with data from the broader Levantine archaeological record, demonstrate that regular or habitual fire use developed in the region between 350,000–320,000 years ago. While hominids may have used fire occasionally, perhaps opportunistically, for some million years, we argue here that it only became a consistent element in behavioral adaptations during the second part of the Middle Pleistocene.”

Fire provided numerous benefits to humans.  The first probable use, according to Harold Schobert, author of Energy and Society, 2nd edition, was protection.  Fire also provided warmth.  And since groups of people tended to gather around a fire, it aided in social and language development. Richard Wrangham of Harvard University (Catching Fire: How Cooking Made Us Human and Evolution By Fire has argued that by making cooking possible, the use of fire allowed our ancestors to evolve larger, more calorie-hungry brains and bodies, and smaller guts suited for more easily digested food.  It also raised the per capita energy usage of humans dramatically.  (see figure 1-2)

Apes began to morph into humans, and the species Homo erectus emerged
some two million years ago, Mr. Wrangham argues, for one fundamental
reason: We learned to tame fire and heat our food.

     “Cooked food does many familiar things,” he observes. “It makes our food safer, creates rich and delicious tastes and reduces spoilage. Heating can allow us to open, cut or mash tough foods. But none of these advantages is as important as a little-appreciated aspect: cooking increases the amount of energy our bodies obtain from food.”

     He continues: “The extra energy gave the first cooks biological advantages. They survived and reproduced better than before. Their genes spread. Their bodies responded by biologically adapting to cooked food, shaped by natural selection to take maximum advantage of the new diet. There were changes in anatomy, physiology, ecology, life history, psychology and society.” Put simply, Mr. Wrangham writes that eating cooked food — whether meat or plants or both —made digestion easier, and thus our guts could grow smaller. The energy that we formerly spent on digestion (and digestion requires far more energy than you might imagine) was freed up, enabling our brains, which also consume enormous amounts of energy, to grow larger. The warmth provided by fire enabled us to shed our body hair, so we could run farther and hunt more without overheating. Because we stopped eating on the spot as we foraged and instead gathered around a fire, we had to learn to socialize, and our temperaments grew calmer.

     There were other benefits for humanity’s ancestors. He writes: “The protection fire provided at night enabled them to sleep on the ground and lose their climbing ability, and females likely began cooking for males, whose time was increasingly free to search for more meat and honey. While other habilines” — tool-using prehumans — “elsewhere in Africa continued for several hundred thousand years to eat their food raw, one lucky group became Homo erectus — and humanity began.”


Populations grew by using energy in the form of human labor and fire.  With this growth came the domestication of animals and the need for open land.  Fire was used for this purpose and with that came a certain amount of degradation of the local environment. When the availability of food, firewood, and other resources became limited, humans picked up and moved on. This allowed time for the limited damage done by human habitation to the environment to heal.  With small, sparse populations, the land was able to regenerate itself before humans returned.  In other words, this pattern was sustainable.

Humans gradually learned the skills required to put down roots – both literally and figuratively. 

We found we could more efficiently survive by growing our food instead of chasing it.  Our first civilizations stemmed from the development of agriculture, but agriculture required at least double the amount of energy as hunting. This additional energy was provided by animals and, in some cultures, slaves.

Figure 1-1 shows the relationship between the various stages of human development and the amount of energy we’ve consumed per capita. Though they make the point well, the numbers in this graph are old, humans currently use 2.3 times more energy than we did in 1971.

Figure 1-1: Estimated Daily Consumption of Energy per Capita at Selected Historical Points

Adapted from: E. Cook, “The Flow of Energy in an Industrial Society, ” Scientific American, 1971 p. 135.
(Used with Permission)


Stay Warm and Healthy!

See you next week!


In addition to clean energy, another passion of mine is photography. The intent of my photography is to showcase the natural world and remind us of our intimate connection with nature.

It is my hope that you will enjoy this photograph and that it will inspire you to take positive action to help protect our environment.

November Tree
Bear Brook State Park
Photo: Wes Golomb

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