In recent years, humans have become increasingly concerned with their effect on the planet and its ecosystems. In the popular view, these problems are new and unprecedented in human history. While it is probably true that our impact on the environment on a global scale has never been as great, the difference is simply the scale on which our actions are being taken. Situations that previously were local or regional in scope have now become global, owing to the increasingly sophisticated technologies that we have developed and our ever-increasing population. As an examination of the impact of ancient humans on the environment illustrates, however, the current impact fits into the general pattern that the degree to which humans influence their environment is determined by their concentration and the sophistication of their technology. Contrary to the popular view which sees ancient humans as either benignly living with their environments (see Note 1 below) or as leading miserable short lives during which they were at the mercy of those environments, archeology tells us that humans have been interacting with and affecting their environments since the beginning. As Neil Roberts comments, humans' impact on landscapes began "even before landscapes had become recognizably modern." (Note 2).
My purpose in this paper is to illustrate some of the ways ancient humans, using a variety of technologies, altered the environments they lived in. Before I begin, however, I would like to emphasize that discussing human "impact" on the environment implies human action was detrimental to the environment. In this paper, I shall define "impact" as any change in the landscape of a place resulting from human actions, intentional or unintentional, which is not inherently a positive or negative change. Although we have recently tended to see any human caused change in ecosystems as "destructive" to the ecosystem, our survival as a species has been possible because we have changed the world around us. Thus I would like to suggest that whether ancient humans' effects were positive or negative depends which species' point of view one measures from. An action that helps one species almost certainly harms another. Ancient humans were acting within and co-evolving with environments that were also being influenced by climate changes and other natural phenomena, and thus it is difficult to say what the "natural" state of the environments were before humans started "degrading" them. (Note 3) I believe this must be kept in mind while discussing ancient humans' impact.
The way in which peoples have influenced ecosystems has been largely determined by the technology available to them. Defined by Merriam-Webster as "the practical application of knowledge," (Note 4) technologies are human inventions such as ideas, techniques or tools which have been used by humankind to increase the likelihood of survival. Technologies have co-evolved with cultures, in turn influencing and being influenced by changes physical environment and societal structure.
One of ancient humans' greatest effects on their environments was the result of using fire. Though it is not clear when humans first learned to use and control fire (Note 5), it is certain that the use of fire was widespread by the beginning of the Late Pleistocene (Note 6). A vivid example of the use of fire occurs in Australia, where 50,000 years b.p. human use of fire had altered vegetation patterns and perhaps even climatic patterns enough to cause the extinction of numerous large mammals, called megafauna. (Note 7)
Fire was used in Australia for a variety of tasks. Burning certain areas could force animals to flee, allowing for easier hunting. It could also increase the availability of animals to hunt by creating new grasslands on which these animals graze. Clearing bush was made easy by the use of fire, permitting the open spaces necessary for both ritual walkabouts and easy transportation in densely forested landscapes. Fire was also helpful for gathering. Burning can be used to synchronize the kernel cycle of different areas, allowing for more uniform harvest times and, thus, less monitoring of the landscape. Fire cycles increase the productivity of certain plants, such as cycads and macrozamia. Indeed, pyrophytes like eucalyptus literally thrive in the areas disturbed by burning. By burning, the residents of Australia were able to increase the available populations of certain plants which were desirable for various reasons. Both Stephen Pyne and David Yen argue that although the first truly domesticated species are not found in Australia until the eighteenth century arrival of the Europeans, fire was used by the native populations to domesticate the whole environment and manage the ecology in a way that was favorable to their needs, at least in the short term. In the long term, fire created an arid environment less favorable to humans.
Obviously, such large scale alteration of previous vegetation patterns had serious implications for animal species that depended on plant species not favored by this burning. It is the case of one such species that has provided the most convincing evidence to date that it was human burning which caused the megafaunal extinctions by changing vegetation and climate so that the megafauna could not exist. That species is the 80-100 kg, flightless bird, Genyornis newtoni. A browser, not a grazer, this bird relied on the plants which grew at the edge of wooded areas, plants which would have been much less common in burned environments. Using amino acid racemization, a reliable dating method, on pieces of Genyornis newtoni eggshell, Glenn Miller and his team showed that this bird disappeared continent wide 50,000 years ago. Another group of scientists led by Richard Roberts demonstrated that multiple species went extinct during a time of stable climate and within 10,000 years of the arrival of humans. Taken together, these two reports conclusively show that the megafaunal extinctions were the result of human action, primarily burning.
Fire use was not constrained to Australia. In North America, it is clear that populations used fire in a similar fashion. The North American fossil record also shows multiple extinctions of megafaunal within the general timeframe of human burning, but because no one has proved these extinctions were simultaneous, it is not certain that human burning caused the North American extinctions. Evidence of using fire to, in a sense, "domesticate the environment" has also been found in Amazonia.
Another set of development that increased the degree of human effect on the environment involved the changes in hunt-gatherer subsistence patterns, social structures, and ideologies that have been called the Broad Scale Revolution. (Note 8) These upper Pleistocene changes mark the emergence of more complex hunter-gatherer societies, and accompanied the evolution of anatomically modern humans. The changes were widespread and diverse. Highly mobile populations became sedentary, and population densities increased, along with competition for resources and the beginnings of social stratification. Hunter-gatherer populations expanded their resource bases, perhaps in response to decreased mobility from increasing population densities or in response to climatic shifts. (Note 9) Trade networks and occupational specialization developed.
These changes, which altered humans' relationships with ecosystems, were accompanied by technological developments, although it is hard to say whether environmental changes were the result of these developments or these developments were forced by changes in the environment. Probably the most important "technology" developed is storage, whether as physical means of storing food (such as deep pits in the permafrost or smoking and salting of meet), or as sharing with societal obligations (called "social storage"). Storage allowed people to spend less time hunting or foraging and more time doing other things, including perfect technologies. This additional leisure time also led in some cases to the development of religions or belief systems, which could change the way humans viewed their environment. Other technologies developed which allowed for the exploitation for the first time of r-selected species, which are small and reproduce by producing lots of offspring on the hope some will survive. (Note 10) These included barbed harpoon points for catching smaller fish, bags and containers for gathering seeds of grain plants, specialized stone microliths that aided in the harvest of these seeds, and grinding stones, which allowed grains to be used as food.
Such broad-scale changes of course had a significant effect on the environment. Human use of fire may have caused megafaunal extinctions in the Americas, and probably did in Australia, as has been discussed above. Greater population densities forced populations to adapt to exploiting previously ignored r-selected food resources; these new food-collecting strategies exerted greater selectional pressure on various plant and animal species, changing the composition of ecosystems. Early sedentary populations are associated with the evolution of new commensal species such as Mus musculus, the house mouse, which coevolved with humans, benefiting from the disturbed environmental conditions, protection from predators, decreased numbers of competitors, and sources of food from human waste that were found around permanent human settlements. By allowing greater concentrations of people to live in one place, the development of storage and more intensive use of food resources aided the development of more complex societies and eventually agriculture, developments which would cause changes in the environment.
Whether through their use of fire in Australia or because of increasing population density, increasing sedentism, and the development of storage and specialized tools for food collection and processing, humans have been influencing the composition of landscapes since before modern landscapes existed. The nature and scale of their impact has largely been determined by their concentration and by the specific technologies they employ. In general, as the population density of an area increases and/or technology becomes more sophisticated, human impact increases.
Notes and Sources:
1. This view may illustrate the nature-consciousness of primitive peoples by pointing to social traditions about resource use, or to nature-based religions as proof that these peoples lived in harmony with their environments. For an archeologist's assessment of the truth of this romanticized view in the context of the native peoples of North America, see The Ecological Indian: myth and history by Shepard Krech III (New York : W.W. Norton & Co., 1999).
2. N. Roberts. The Holocene:
an environmental history. Malden, Mass.: Blackwell Publishers, 1998. Pp 86.
3. For a useful discussion of a framework from which to approach this subject, see the first three chapters of Human Impact on Ancient Environments by Charles L. Redman (Tucson: Univ. of Arizona Press, 1999.) The rest of his book presents the same types of examples I am discussing here from a variety of historical periods, as well suggesting the role archeology can play in informing how we address current environmental issues.
4. "technology" in Merriam-Webster online dictionary. http://www.m-w.com/home.htm
5. For various arguments about the first evidence of fire use, see "Geological analysis damps ancient Chinese fires," Wuethrich, Bernice; Science 07/10/98, Vol. 281, Issue 5374, p. 165; "Did Homo Erectus tame fire first?" Balter, Michael; Science 6/16/95, Vol. 268, Issue 5217, p. 1570.; and "Fired Up," McCrone, John; New Scientist 05/20/00, Vol. 166, Issue 2239, pp. 30-34.
6. This was around 100, 000 years ago, or years before present (b.p.). By convention, the present is 1950.
7. Information in this and the following paragraphs comes from a variety of sources, including the author's lecture notes for a class entitled Seeds of Change taught by Michael Spiers at Swarthmore College during the spring of 2002, "The Domestication of Environment." by D. Yen in Foraging and Farming: the evolution of plant exploitation, edited by D. Harris and G. Hillman (London: Unwin Hyman, 1989, pages 55-72); Burning Bush: a fire history of Australia by S. Pyne; and two National Public Radio clips, one entitled "Megafauna Extinction" from January 8th, 1999, and the other "Aboriginal Climate Change" from March 17th, 2002. Also see G. Miller et all in Science volume 283 from 1999 and Roberts et all in Science volume 292 from 2001.
8. Information cited in this and the following paragraphs come from the author's lecture notes as described in note 7 above, as well as Ellen, R. "Modes of subsistence: hunting and gathering to agriculture and pastoralism," in The Companion Encyclopedia to Anthropology, ed T. Ingold, New York: Routledge, 1994.; and Price, T.D. and J.A. Brown. "Aspects of Hunter-Gatherer Complexity," in Prehistoric Hunter-Gatherers, T. Price and J. Brown, eds. San Diego: Academic Press, 1985.
9. Other populations such as mammoth hunters of the Central European Plain dealt with these pressures by shifting to specialized economies based on the extensive use of a few species.
10. The opposite is k-selected
species such as mammoth, who produce fewer offspring, but give these offspring
more care in order to give each offspring a higher chance of survival. Earlier
subsistence patterns had tended to focus on k-selected species.
Read the author's other essays:
Population and the Environment: Are We Doomed?
Yucca Mountain and Nuclear Waste (Final Project)
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