Fire is the fundamental human technology, the foundation of everything that came after in human societies. Controlled fire transformed our diet, physiology, psychology, language, social structure, technologies, and our relationship to the rest of nature.
Some archeologists believe that fire management provided the change that distinguished us from other social mammals. Although we are enamoured by the power of modern technologies, an understanding of our relationship with simple fire informs us about genuine solutions to our ecological impasse.
Canadian tarsands: Humans have been burning fuels for a million years. Fire transformed human society, caused early forest depletion and species extinctions, and our energy use today now exceeds Earth's capacity to sustain. © Jiri Rezak.
The discovery and use of fire
Non-human animals are known to use natural fire. Hawks, cheetahs, and other species hunt prey disrupted by fire. Savanna chimpanzees are not intimidated by fire, behave sensibly around it, and will hunt food after a fire passes. Humans likely used fire for millions of years, before they could ignite or control it.
Fire maintenance likely began among Homo erectus communities, who moved from forest to savanna habitats. Fire ignition followed, and may have contributed to a cognitive advance, the use of intermediaries — tinder and kindling — to ignite a slow burning fuel. Evidence of intentional fire exists around a million years ago, in archeological sites from Chesowanja, Kenya to Yunnan Province, China.
Fire use by humans preceded controlled fires, and firemaking required and augmented advanced human mental powers. Fire is the fundamental human technology. Public domain image.
Three hundred thousand years ago, fire-based technologies existed throughout Eurasia, including stone hunting tools warmed to improve working qualities and hafting glues that required fire to prepare. Fire allowed humans to seize caves previously occupied by other large, fierce mammals. Fired pottery existed 20,000 years ago, and metallurgy 5,000 years ago. During this long history of fire use, hominids distinguished themselves from all other large mammals. Meanwhile, fire revolutionized human society.
The need for fuel and fire maintenance likely led to a division of labour among early hominids. Human communities grew more stationary around the fire and hearth, transforming vocal communication, language, and eventually story-telling. During a million years of fire management, the Homo genus evolved a waking day of about 16 hours, much longer than most other mammal species, and gained survival advantages that our species enjoys to this day.
Cooking may have been fire’s greatest social impact, since it made more calories available from foods, reduced the energy cost of digestion, and freed that energy for other enterprises, tool-making, art, and social interaction. Every species is constrained by its available energy, and cooking gave humans an energy boost, which led to additional technological innovation. These developments also changed human brains, mating habits, and gender divisions of labor. Among most primates, males and females gather the same food. Once hominids controlled fire, males spent more time on wide range hunting and defense, and females and elders refined social ritual and language around the hearth. Fire contributed to food sharing and longer childhoods, and thus greater learning potential.
However, the costs of fire can be high. Cooking fires make a stationary community more vulnerable to predators or invasion, so security became a more constant labour. Fuel-foraging depleted local brush and trees. Some Neolithic settlements, such as Çatal höyök in modern Turkey, provide evidence of long distance foraging for firewood and of woodland management. Fire allowed metal technologies, which led to early mining, which required more wood-burning, and led to localized mineral depletions and deforestation.
One of humanity’s oldest surviving stories, the Epic of Gilgamesh from Sumer, at least 5,000 years old, begins in a settlement protected by kiln-fired brick walls. The story discusses forest depletion, drying marshes, social oppression, and abuse of power, all linked to the power of controlled fire. We witness here, fundamental dysfunctions that remain with society today.
Fire, extinctions, and ecological overshoot
By 50,000 BC, long before agriculture, Homo sapiens population growth surged, and anthropologists find evidence during this period of animal and plant extinctions, primarily caused by controlled human fire used as a hunting technique.
Around 47,000 BC, humans arrived in Australia, regularly set fire to the landscape to flush prey, and eradicated dozens of large mammals, marsupials, reptiles, and flightless birds. The burning also caused localized climate change by reducing water vapour. Declining cloud cover shifted the monsoon cycle, the Nullarbor grassland became desert scrub, and once abundant Lake Eyre became a salt flat.
When human communities advanced into the Western Hemisphere, about 75% of large mammals (mastodons, mammoths, giant beavers, bears, and tigers) vanished. Similar mass extinctions occurred when humans arrived in Madagascar, Hawaii, and in New Zealand.
How does this knowledge help us now? We can see that humanity did not require industrial fossil fuel technology to cause species collapse and climate disruption. Sheer numbers, stone tools, and a plentiful external energy source were sufficient. University of British Columbia professor Dr. William Rees, developer of "ecological footprint" analysis, explains that certain mammalian traits led our species to overshoot ecosystem resources even prior to industrial technology. Like other large mammals, humans are "K-strategists," ("K" stands for a habitat’s capacity, German Kapazität), which means we have evolved to occupy all accessible habitats and use all available resources.
Evolutionary success has costs and, without restraints, can be fatal. Nature taught us to be aggressive and rapacious, as survival skills, but didn’t teach us how to stop. We have to do that ourselves. To solve our ecological dilemma, humanity has to reverse its expansion. Continued growth for a successful species that has overshot its habitat will lead to collapse.
External energy and Food
When a plant or animal’s energy use relies directly on the sun or food, habitat capacity acts as a restraint on growth, and each species remains in dynamic homeostasis as witnessed in predator-prey cycles or in our own gardens. In 1922, Polish-American biophysicst Alfred Lotka, who developed predator-prey dynamics, published "Contribution to the energetics of evolution", proposing that evolution was driven by the ability to access available energy. Trees grow more leaves so they can transform more energy. The sharp eyes of the hawk help it process more energy, with less energy cost.
All plants and animals other than humans rely solely on energy from the sun or food, internal, which biologists call "endosomatic" energy. The energy humans derive from fire, work animals, fossil fuels, hydro dams, or solar panels, is "exosomatic," energy retrieved from outside our bodies. The aristocracy throughout history have also gained exosomatic energy from slaves and exploitive wages for labour.
The average human requires about 2,400 food calories (kilo-calories) per day, about 3,600 megajoules (MJ) each year. In pre-fire hominid societies, each person consumed roughly this much energy from food. Fire provided humans with about 15,000 MJ of extra energy each year, 4-times more external energy than internal energy from food, a 4:1 ratio. About a billion people today still live roughly on this fire-level energy budget. In the poorer nations such as Haiti and Senegal, the average energy consumption is about twice this level, an 8:1 ratio of exosomatic energy.
However, in rich, industrial nations, the use of external energy soars. Europeans use about 40-times as much external energy as they get from food, and the average US, Canadian, or Scandinavian citizen uses about 90-times as much external energy. Among the super-rich, jet-set, multiple-home elite, this energy use can skyrocket to 1000-times as much external energy. We could solve most of our energy problems by limiting frivolous energy waste among the rich.
Most industrial nations spend 12 -16% of their energy budget to grow food. The so-called "green revolution" was really a black revolution, relying on fossil fuels for fertilizer, machinery, transport, and packaging of food. A study by Mario Giampietro and David Pimentel shows that food delivered to the consumer in North America requires ten-times more energy than the food contains. When we add the energy cost of storage, cooking, and waste, industrial food has a negative net energy of over 12:1. Nate Hagens, who teaches "Reality 101" at the University of Minnesota, points out that humanity’s food today is not an energy source, it is "a vast energy sink." In the natural world, spending more energy to get food than the food contains proves unsustainable.
Since 80% of our energy use comes from fossil fuels, we are essentially eating oil. To achieve this level of food production, industrial agriculture has depleted soils, spread toxins, disrupted nutrient cylces, and launched an era of rapid global heating. In short, humanity has used Earth’s vast energy stores to overshoot their ecological habitat.
Humanity’s destructive consumption of exosomatic energy started with the advent of controlled fire, and that basic fire economy has never disappeared. Firewood use never declined and remains an important source of energy for humans. Coal did not replace wood, but only added to our energy consumption. Oil, gas, and nuclear power did not replace coal and hydropower, but only added to our energy consumption. One might imagine "replacing" oil with renewables, but so far, renewable energy simply adds more energy. Historically, humans only stop using an energy source when it is depleted.
Learning to reduce our energy consumption — not just finding more — remains at the heart of our ecological challenge.
Rex Weyler is an author, journalist and co-founder of Greenpeace International. The opinions here are his own.
World energy consumption by source: Coal did not replace wood burning, but rather added more energy for human consumption. Likewise, oil did not replace coal. Growing to consume more energy is a trait of all species, until a species overshoots its habitat. Human energy use has now increased to an unsustainable scale. Conservation has to a part of any genuine sustainable energy future. Graph by Gail Tverberg, Our Finite World.
Human use of fire:
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Discovery of Fire by Humans, J. Gowlett: Royal Society
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Overshoot, energy, and food:
Historic Overshoot, R. Weyler, Deep Green
Alfred J.Lotka, "Contribution to the energetics of evolution"; Proc Natl Acad Sci, 8, May, 1922
Energy content of food: Food and Agriculture Organization. UN
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Fertilzer energy use, Fertilizer Institute