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Discovering Fire: How We Became Pyrophiles

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Editor’s note: With the approaching premiere of Fire-Maker: How Humans Were Designed to Harness Fire and Transform Our Planet, a new documentary from Discovery Institute featuring Michael Denton’s work, we asked Dr. Denton for his comments on a well-timed new research article in Evolutionary Anthropology. See the trailer here:

In an interesting article, “The Pyrophilic Primate Hypothesis,” recently published in Evolutionary Anthropology, the authors ask: How did hominins come to create, use, and control fire? They argue that our evolution into active pyrophiles came about not as claimed by some — that is, through serendipitous or accidental discovery — but rather through an active adaptation to progressively drier fire-prone environments which characterized the African savannah from approximately 3.6 million years ago to the present.

Africa, they point out, has been referred to as “the fire continent” because of widespread burning throughout its sub-Saharan grasslands. This stabilized at more or less current levels during the past 1.8 million years. The authors hypothesize that beginning by

exploiting the foraging benefits produced by naturally occurring fires [including] a reduction in food processing costs [because of the “natural cooking” of foodstuffs — including geophytes such as tubers, corms, rhizomes], fire control in the form of simple landscape burning and purposeful cooking followed as a consequence of targeting the foraging benefits of fire.

While the authors may be right and the overall scenario they propose seems reasonable, their answer to the central question leave out any consideration of important environmental factors that made possible mankind’s exploitation of fire in first place.

To begin with, fire or combustion — the reaction between reduced carbon and oxygen — is of course a natural chemical reaction that long predated man’s creation and mastery of this primal force. Intriguingly, fire is a gift of life. As Stephen Pyne describes it:

Fire takes apart what photosynthesis has put together; its chemistry is a bio-chemistry. Fire is not something extraneous to life … it is something that has emerged out of the nature of life on Earth.

Moreover it is only because of unusual features of the reaction between carbon and oxygen that mankind was able to master this “primal reaction.”

Although combustion produces vast amounts of energy, its vigor is greatly attenuated by the relative un-reactivity of carbon and the relative inertness of oxygen in ambient conditions. This is experienced in the difficulty of initiating a camp fire, which requires an input of heat to get things started — a match, lighter, etc. It is only because of the attenuation of the reaction that organisms such as ourselves, made up of reduced carbon compounds, are stable in our current oxygen-rich atmosphere. As Roman Boulatov points out:

The biosphere benefits greatly from [the] inertness of O2 as it allows the existence of highly reduced organic matter in an atmosphere rich in a powerful oxidant. But such inertness also means that rapid aerobic oxidation will occur only if energy is put into the system to overcome the intrinsic kinetic barriers [heat in the case of a camp fire] or the reaction is catalyzed (i.e., the kinetic barriers are lowered by stabilizing otherwise high energy intermediates).

And there is another factor that attenuates the vigor of the reaction between carbon and oxygen: the existence of a fire diluent in the atmosphere, nitrogen, which retards the rate at which flames spread. Without the relative inertness of the reactants, carbon and oxygen, and in the absence of a diluent in ambient conditions, the carbon-oxygen reaction would be an “explosive phenomenon” leading to catastrophic uncontrollable conflagrations that no hominin would ever have mastered.

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And if it were not for this relative lethargy in the reaction between carbon and oxygen, thenas oxygen-utilizing and -dependent organisms — necessarily so as only oxidation provides sufficient energy to support advanced metabolism in carbon-based life forms, extracting copious quantities of vital elements from an oxygen-rich atmosphere — we would suffer spontaneous combustion. Neither the controlled use of fire nor the existence of our type of advanced forms of life, utilizing oxygen, would be possible were it not for these fortuitous elements of fitness in nature.

Again, cooking aids digestion, as they point out, offering “reductions in chewing effort, together with chemical alterations in food that increase digestive efficiency, lower handling costs.” But cooking has these effects only because of the characteristic instability of organic compounds that make up “foods.” As temperatures rise, organic compounds begin to decompose, initiating the process of digestion. Meat softens on heating because the collagen that makes up the tendons and fibrous sheets is converted to gelatin that offers no resistance to a knife or teeth. These beneficial physical and chemical changes that accompany cooking are elements of fitness in nature that have nothing to do with human ingenuity.

And the benefits of cooking are not the only benefits that accrued to early man on his mastery of fire. Fire provided warmth, warned off predators, and assisted in tool manufacture by the hardening of wood and bone implements.

Man’s ability to exploit other fire-assisted technologies acquired millennia after fire was first tamed — such as ceramics and metallurgy — was also due in large part to an underlying fitness in nature to those ends. Without the ready availability of metal ores and the fact that metals can be extracted from their ores at temperatures attainable with wood or charcoal fires, metallurgy would never have been developed and we would still be living in the Stone Age.

Photo credit: Tony Webster [CC BY 2.0], via Wikimedia Commons.