The human species, like virtually all species, is heterogeneous. This condition of Darwinian natural selection is thus met, as is the obvious condition of reproduction and the proven condition of inheritance through genetic information. But human beings are not completely at the mercy physiology; natural variation is only the starting place of our selective advantage. We, like no other species on earth, have the capacity to identify gaps between our inherited nature and the adaptations that would be ideal for a given environment, and to alter ourselves, or our environment, accordingly. I am contending that this is the defining characteristic of humankind and the key to our hegemony over this planet.

            Five million years ago though, this future must have looked far from guaranteed. For the first 4 or so million years of hominid existence our evolutionary predecessors were social apes, learning to meet the challenge of survival in strange and sometimes treeless environments. The move out of the forests and into the grassland catalyzed the bipedal revolution, but beyond that, early man's ability to manipulate his surroundings was restricted to the crafting of stone tools which, compared to the teeth and claws of large prehistoric predatory cats, fell far short of propelling them to the position of dominance that we enjoy today. But our ancestors did have relatively big brains, a condition that suggests they were poised to start their march towards the domination of all terrestrial ecosystems, awaiting only the right spark to light their neural kindling. Making fire would in turn beget a multitude of different mental and cultural advances -- to utilize fire effectively requires social order, an unprecedented level of abstraction and communication, and a division of labor -- all where before there was little more than dormant potential. But is this an accurate description of our cultural genesis?  Circumstances make it appear unlikely, for harnessing fire may have been necessary for an evolutionary cousin of ours, Homo erectus, to survive a million and a half years before we even emerged on the scene, yet he failed to develop the peripheral technologies -- along with their corresponding feedback loops --that has made the unremitting march towards social complexity almost assured in modern man.

            That fire was controlled by some species of Homo sometime during the last 2 million years is about all that the scientific community can agree upon. Who was actually responsible is a question with profound ramifications for the uniqueness of Homo sapiens and the nature of social progress. Homo erectus is our primary competitor for this cultural achievement; in fact a quite convincing argument can be made for him in light of his physiological and mental capacities, environmentally determined needs, and the material evidence that has been uncovered recently by paleoanthropologists.

            Erectus was the first humanoid species to leave Africa behind, an achievement that seems impossible to me without first having mastered fire. Their remains have been found throughout Europe and Asia, raising the question: how could early man survive a winter as far north as the Arctic Circle (60 degrees N) without clothing or fire? Anthropologists from the Max Planck Institute of Evolutionary Anthropology have made a compelling argument for the origin of clothing, dating it through the co-evolution of body lice. There is usually only one species of lice per host and body lice live in clothing, making it likely that clothing dates back only 42-72,000 years, the established age of the species inhabiting it (Travis 1). Hominids must have learned to make fire before they made clothes, judging simply by the amount on conceptual and technical skill needed for each, which makes the most extreme "big bang" date for harnessing fire, 40,000 ya, seem unreasonable. We clearly cannot deny all of our ancestors the creative power we so pride ourselves on, but who among them shared our proclivities, and to what degree, is still largely unknown. Even though Homo erectus never achieved total supremacy, very few mammalian species have been able to inhabit as widespread a territory, and without fire, this great tolerance and relative success seems highly improbable. 

            Some of the most striking and concrete evidence for erectus' dominion over fire comes from the work of Prof. Rowlett of the University of Missouri-Columbia. His study of two possible ancient campsites in Kenya has provided evidence of the use of fire over 1.4 million years ago. At the possible sites (Koobi Fora and Chesowanja) he discovered half-meter wide "lenses" of orange ground that, through thermoluminescent dating, were shown to be the result of some sort of the thermal activity. Lightning strikes make much smaller "lenses", and bushfires typically only reach 100 degrees C -- one quarter the heat these fires produced, suggesting an artificially created environment that allowed the fire to thrive. Furthermore, Rowlett was able to identify the types of plants burned by analyzing the residual silica deposits and discovered that palm wood was by far the most abundant. (McCrone 32-33).Either one of the best kinds of wood for making a fire happened to burn at an unusually high temperature in a series of small, circular flare-ups, or the wood, heat, and distribution were selected and manipulated by an intelligent agent. Though I understand the reluctance to attribute intelligence to erectus -- after all, fire excepted, their material culture never moved beyond stone tools -- the former possibility requires one to believe in a coincidence that seems much more unlikely than an intelligent erectus.

            Certainly the size of erectus' brain does not disqualify them from this achievement. The smallest known erectus brains are estimated to be roughly 900 cc, a little under 3/4 the size of Homo sapiens' brain (Kreger 2). If they had a capable brain and were subject to environmental pressures for over a million years that would have made fire an invaluable resource, then why no fire? And if one is willing to concede that erectus may have made crude campfires, then why no further cultural development? Why did erectus fail to achieve hegemony in a million years when we have been able to do so in less than 150,000 years? That Homo sapiens is the last-man standing (as opposed to our contemporaries  floresiensis and neaderthalensis) speaks to something unique in our nature as the source of our success rather than a environmental change that would made the world a more habitable place in general for hominids.

            More so than anything else, the geographic distribution of erectus makes me inclined to accept their ability to use fire, though not without reservations. After all, fire is such an essential technology with so many obvious applications (either apparent or exceedingly easy to discover by accident) that it is almost inconceivable that it did not catalyze further development. Erectus had to have been familiar with natural fires and the benefits of the carnage they left in their wake -- improved visibility for hunting, greater mobility, and unlucky corpses crispy and delicious for the scavenging. These benefits would have been magnified and routinized by controlling fire, theoretically providing erectus with a hefty increase in caloric intake. Now armed with a big brain and an increased amount of energy available for further growth it seems impossible that erectus stagnated the way it did. The most conclusive evidence only indicates that fire was cultivated intentionally by erectus. It is possible erectus never learned to make fire, a crucial distinction when considering the level of agency man had in shaping his environment.

            Either erectus, against all odds, did not use fire as a tool at all and managed to survive in freezing climates by virtue of their "toughness", or, much more likely, they did use fire but lacked the ability to understand all the uses as well as the significance of their discovery. Thus, there must be some cognitive mechanism in us sapiens that allowed us to triumph where erectus failed. Language is often pointed to as the missing agent, but language is less an agent than the manifestation of certain cognitive predilections; certain symbolic, abstract functions buried deep in our minds. Cognitive scientists and anthropologists working together need to continue pursuing this question, looking at the mind we have now and continuing to develop a more complete picture of our evolutionary past. Somewhere within the failure of erectus and the success of sapiens lies the true key to our global hegemony, but with so little definitively known about our late cousin it is impossible at this point to say just what that is.

References

Fired up. McCrone, John, New Scientist, 05/20/2000, Vol. 166 Issue 2239, p30, 5p, 2 maps, 10c

A Survey of Human Evolution, If This is a Man and Meet the Relatives, The Economist, December 24th 2005

The Naked Truth? Lice hint at a recent origin of clothing. Travis, John, Science News, Aug. 23, 2003; Vol. 164, No. 8 , p. 118. http://www.sciencenews.org/articles/20030823/fob7.asp

Homo Erectus. Kreger, David, http://www.archaeologyinfo.com/homoerectus.htm, 2005