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Homo Sapiens or Homo Igniferens?

Wednesday, September 19, 2012

We are not simply beings that use energy; we are beings that exist only because we harnessed energy, and our use of energy has shaped our bodies and culture for millions of years.

Editor’s note: This essay is the second in a series that will explore issues in energy literacy and energy policy.

[Fire] provides warmth on cold nights; it is the means by which they prepare their food, for they eat nothing raw save a few fruits... the Andamanese believe it is the possession of fire that makes human beings what they are and distinguishes them from animals. —A. R. Radcliffe-Brown1

When it comes to energy, most discussions focus on narrow specifics: Should we use less oil? Should we use less coal? More nuclear? Wind power? Solar power? Should we use less power altogether? All of these questions are important, of course, but they are too often discussed in the complete absence of context. The bigger picture is that biology and anthropology tell us something very interesting about human beings: We are not simply beings that use energy, we are beings that exist only because we harnessed energy, and our use of energy has shaped our bodies and culture for millions of years.

All known human societies, from the most advanced to the most primitive, rely on the controlled use of fire (or more advanced forms of energy) for cooking, lighting, and protection. And human beings are the only species known to do so (apes taught to smoke cigarettes don’t count). Virtually all of society’s advances in security, food availability, physical comfort, time for study and to practice the arts, and ability to influence the world stem from the direct or indirect use of energy. In a real sense, we might best be identified as homo igniferens: Man who ignites fire.

Anthropologists have long struggled to figure out exactly when primitive human beings first used fire constructively in their lives. For most of human history and prehistory, modern humans and their forebears were largely nomadic and could not build structures that were capable of surviving for hundreds of years, much less thousands or millions. And often, what did get built or occupied for a long period was buried or erased by natural events, such as glaciations, rising sea levels, land subsidence, and so on. The small fires that early humans would likely have used would not have left much for others to find even a few years later, much less a few million. As a result, the further back into the past that scientists try to look, the less likely they are to find permanently occupied areas where humans might have repeatedly built fires.

Despite these limitations, archaeologists and anthropologists have discovered evidence suggesting that ancient humans were fully in control of fire—from its lighting to its maintenance and use—at least 1.5 million years ago.

Fire and Human Development

Some anthropologists believe that humanity’s relationship with fire goes much further back in time, into our fairly distant prehistory. These anthropologists argue that primitive man’s use of fire for cooking, clearing land, lighting, hardening tools, and protecting himself from predators not only improved survival and reproduction, but also led to changes in the human genome, brain development, digestive system, dentition, hairiness, and the many other characteristics that define human beings today.

Some anthropologists argue that primitive man’s use of fire led to changes in the human genome, brain development, digestive system, dentition, hairiness, and the many other characteristics that define humans today.

This tantalizing hypothesis is fleshed out in two recently published books examining the relationship of fire to human development. In Richard Wrangham’s book Catching Fire: How Cooking Made Us Human, the focus is culinary. Wrangham is primarily interested in how cooking food increased the calories available to primitive man, changing our ancestors’ lives and biology. In Fire: The Spark That Ignited Human Evolution, Frances D. Burton focuses on how exposure to firelight might have altered hormonal activity in the brains and bodies of humanity’s primitive ancestors, leading to changes in the structure of the human brain as well as the development of more complex forms of social interaction.

Wrangham’s observations that fire increased the number of calories available to early humans (as well as that cooking made possible eating tough, stringy, large-animal game meats) suggest a human relationship with fire dating back about 2 million years. As Wrangham observes, “Humans do not eat cooked food because we have the right kind of teeth and guts; rather, we have small teeth and short guts as a result of adapting to a cooked diet.” Wrangham also notes that experiments with rats, snakes, and, in a few cases, human beings show that softening and cooking food makes it much easier to digest, allowing more calories and other nutrients to be extracted. For example, while raw starchy foods such as potatoes are digested poorly, cooking them vastly increases their digestibility. The same is true for eggs and meat. And interestingly enough, humans aren’t the only ones who prefer cooked food; chimpanzees, other apes, and insects do, as well.

Having observed that our modern-day simian relatives prefer their food cooked, and understanding that changes in diet often precipitate major changes in the biology of organisms, Wrangham casts his eye backward, looking for rapid changes in human development as proxy indicators for when fire may have been harnessed to cook food. Wrangham ultimately settles on a major shift in human living and mobility: The change from a largely tree-dependent lifestyle to a more ground- dependent lifestyle. He notes:

Having controlled fire, a group of ancient human ancestors called habilines learned that they could sleep safely on the ground. Their new practice of cooking roots and meat meant that food obtained from trees was less important than it had been when raw food was the only option. When they no longer needed to climb trees to find food or sleep safely, natural selection rapidly favored the anatomical changes that facilitated long-distance locomotion, and led to living completely on the ground. 

Wrangham puts this transition in lifestyle and climbing ability at the same time as the transition from homo habilis to homo erectus, suggesting that controlled use of fire was accomplished at least 1.9 million years ago.

Understanding energy starts with accepting that we are no longer capable of surviving long, and certainly not very well, without access to fire in its many forms.

Burton, however, thinks that humanity’s ancestral use of fire begins much earlier, perhaps as far back as 6 million years ago. Burton speculates that, at first, this association would be simply a matter of learning to recognize that fire, which is quite common in nature, has benefits, such as leaving behind a bunch of tasty cooked insects. And with an estimated 8 million lightning strikes hitting the earth every day, it’s likely that our ancestors would have seen a lot of it. They might have noticed that smoke from a smoldering tree stump kept away noxious flying insects, made for warmer evenings, and so on, and would thus have desired to stay around spontaneously created fires. Later, the association would have progressed to maintaining naturally kindled fires and, eventually, to discovering how fire is started and gaining full control of this most potent force of nature. Burton also observes that humans aren’t the only ones to like their food cooked, and humanity’s earliest attractions to fire may simply have been an observation that after a fire passes, there are a lot of tasty roasted nuts lying around, not to mention crispy fried insects.

But Burton’s most interesting hypothesis is that harnessing fire could have influenced a hormone that is integrally involved in a vast array of biological cycles. Melatonin, the production of which is suppressed in response to light exposure, is particularly interesting to Burton because it is also involved in the regulation of sleep cycles, reproductive cycles, the onset of puberty (and hence reproductive age), and other fundamental traits that have shaped human development. Burton sums up her view thus:

I conclude therefore that motivation, ability, circumstance, and environment merged to inaugurate this unique relationship to fire around 6 m.y.a. [million years ago]. My view of human evolution is that the acquisition of fire was the engine that propelled the incredibly fast evolution of humans. Directly or indirectly, it affected cognitive processes, social processes, genetic systems, reproduction, the immune system, and digestion, among others. It may even have enhanced hair loss.

Our Dependence on Fire

Whether it began 6 million or 2 million years ago, humanity’s association with fire, and thus our intricate weaving of energy into our lives, is clearly a distinguishing attribute and one that has shaped us in ways numerous, irreversible, and profound. Understanding energy starts with accepting that we are no longer capable of surviving long, and certainly not very well, without access to fire in its many forms, whether it is cooking our food, heating our homes, generating our electricity, powering our cars, or making the clothing that we now need in cold weather because fire let us shed the hairy coats of our ancestors. Politicians like to talk about how Americans are “addicted to oil” or “addicted to cheap energy.” It would be more accurate to say that humans are biologically and culturally adapted to reliance on energy. Are we addicted or adapted? It makes a big difference in how one perceives the role of energy in our civilization.

Having discussed the centrality of energy to the human experience, the next essay in this series will examine the most important question when it comes to energy policy: Energy affordability. For some people in the United States, and many around the world living in a state of energy poverty, no discussion of energy policy is complete without an understanding of how our energy policy choices can affect energy affordability.

Kenneth P. Green is a resident scholar at the American Enterprise Institute. This essay is derived from the introduction of Abundant Energy: The Fuel of Human Flourishing, a supplementary text for college students, published by AEI Press.

FURTHER READING: Green also writes “Energy Abundance vs. the Poverty of Energy Literacy,” “Subsidy-Powered Vehicles,” and “Dissecting the Carbon Tax.” Steven F. Hayward contributes “Unconventional Energy Meets Conventional Politics: Which Will Win?” and “Why the Climate Skeptics are Winning.” Representative Fred Upton discusses “Rethinking America’s Energy Policy.”


1. Richard Wrangham, Catching Fire: How Cooking Made Us Human, p.1.

Image by Darren Wamboldt / Bergman Group

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