Bill Totten's Weblog

Wednesday, May 11, 2005

Nature and the Nature of Man

by William R Catton, Jr

Chapter 9 of Overshoot: The Ecological Basis of Revolutionary Change (University of Illinois Press, 1980)

Detachable Organs

Somewhere in North Dakota I had an unexpected opportunity to discover just what is most ecologically distinctive about Homo sapiens. My family and I were on an automobile trip, driving east on a two-lane road. We had had to slow down appreciably when we became momentarily trapped behind a bicycle. Soft shoulders at the side of the road confined the cyclist to the pavement, and westbound traffic in the other lane prevented us from passing him for a mile or so.

While driving our car for a few moments at the unfamiliar speed of the bicycle ahead of it, I began to notice details of this "traffic obstruction" that otherwise would have escaped my attention. First, because sporadic fuel shortages had already raised the possibility that automobile touring might someday be only a fond memory, I studied the pannier bag hanging astride the rear wheel of the bike, and wondered just what items of spare clothing, et cetera, one might be able to include in one's severely limited luggage when traveling on two wheels instead of four. I noticed also the muscles in the cyclist's tanned calves, and the steady rhythm of his pedaling. Then a slight motion of his head called my attention to a short, stiff wire that curved forward from the bill of his plaid cap. On the tip of the wire was a small round object which I suddenly realized was a thumbnail-sized mirror. Being just a few inches from his face, a mirror small enough to offer negligible wind drag was large enough to give his inboard eye an appreciable field of vision to the rear, without requiring him to turn his neck awkwardly and unbalance himself in looking back over his shoulder.

To all intents and purposes, I realized, this cyclist had "eyes in the back of his head". Before an opportunity arose to speed on past him, another realization had become obvious - that having easy and adequate rear vision could have significant survival value for anyone pedaling a bike on a highway used mostly by automobiles. Then the phrase "survival value" brought Darwin to mind.

Even at automobile speed, crossing the North Dakota prairie gives one time for extended thought. Long after the bicycle tourist was no longer visible in my own rear-view mirror (an artifact I had taken for granted for years), I was contemplating the thousands of generations it might have taken for unfavorable mutations to be eliminated and the rare ones that yield advantageous phenotypic traits to accumulate through natural selection to the point where humanoid creatures might literally have had an eye or two facing aft. I knew it could not happen. Even if humans lacked the inventiveness to shortcut the process by hanging a mirror from a cap, the era in which bicycles would be followed by automobiles was not going to last through enough generations for selection pressures from this situation to influence evolution in that way.

But rabbits had done it! I remembered learning in my childhood that the eyes of a rabbit, positioned at the sides of its head, have fields of vision that overlap slightly in the rear, rather than in front - an evolutionary result of what happened to rabbits if they could not always see any predator pursuing them while they leaped evasively this way and that, heading for cover. <1> For the rabbit, rear vision given him by evolution entailed only minor costs. By slight movements of his head, the rabbit's effective field of sight could span the full 360 degrees, and the fact that his eyes did not face straight ahead was no disadvantage. The rabbit's mode of living did not require the precise depth perception achieved by simians and humans through placement of both eyes in a frontal position permitting stereoscopic vision.

For monkeys, however, there was less survival value in rear vision than in accurate depth perception. To move advantageously through an environment of tree branches, where misperception could mean a fatal fall, required not only a restructuring of mammalian paws (into grasping hands) but a restructuring of the head so that converging eyes would enable distances from branch to branch to be perceived with centimeter precision. <2> An arboreal niche had imposed selection pressures that caused the useful combination of hands and binocular vision to evolve to high perfection. Later, some descendants of creatures thus endowed somehow became surface dwellers. In a new niche, the advantages of depth perception and grasping hands could be turned to new uses. Eventually the result was a proliferation of tool-using. Tools (including weapons) enabled the descendants of tree-dwelling simians to do on the ground things they could not have done so well with only the organs their genes gave them. <3> Chipped stones could cut things teeth couldn't sever - or could be replaced when broken teeth could not. Hollow gourds (and later mud-daubed woven baskets, and still later fired pottery) could carry larger quantities of water a greater distance from the riverbank than a pair of cupped hands could.

Thus there came to be a population of creatures whose way of living involved considerable use of external supplements to their own organic equipment. Insofar as they found it advantageous to use such detachable organs (for that is what tools of any kind are), these creatures became subject to new selection pressures. Now that tool-using was part of their method of coping with their habitat, those with greater ability to devise and use tools would be able (on the average) to leave more progeny than those with less such ability. In short, there was now going to be selection based on ability to make and use detachable organs. Before there had always been selection only for organs (or behavior patterns) capable of coping with the habitat but integral to the creature's body.

Man, the Prosthetic Animal

Nature had achieved, so to speak, an evolutionary breakthrougn. Human extensions of natural organs have come a long way since teeth began to be supplemented with flint scrapers. Some of the supplementary artificial organs have even moved inside. Anyone with a denture (or even a filling) in his mouth can appreciate the technical advances that have, in effect, made teeth repairable or replaceable. Defects or damage in other organs can also be redeemed by artificial means. Anyone who wears glasses can easily recognize the utility of detachable organs, though he may never have thought to apply such a phrase to the device he hangs on the bridge of his nose and hooks behind his ears each morning. His visual acuity depends upon external supplements to the imperfect organic lenses within his eyes.

For a small minority of the human species, the availability of more sophisticated detachable organs has been more than a matter of mere convenience. It has been a matter of life or death. Several good friends come to mind whose hearts have been stopped and surgically repaired. Not only were the tools wielded by the surgeon (as extensions of his hands) vital to these patients; their lives were sustained during the operation by heart-lung machines - temporary substitutes for their own hearts and lungs. Thousands of people have also been enabled to live on after complete failure of their natural kidneys by attaching themselves periodically to a machine that externally performs the blood-purifying hemodialysis no longer possible in their own bodies.

In a milder way, an artificial leg is a tool designed to perform at least some functions of a natural limb. The word "prosthetics" refers to the branch of surgery that deals with replacement of missing parts. <4> It may seem a rather remote and morbid subject, but all humans inhabiting other than tropical environments are users of essentially prosthetic devices - clothing. Homo sapiens can survive where he would otherwise perish by taking from another animal the protective cover normal to that animal as a product of natural selection. Likewise, our shoes have served as a kind of prosthesis for the hooves we were not equipped with at birth, enabling us to walk additional portions of the uneven face of the earth. The evolutionary and ecological significance of such prosthetic devices has been to facilitate the spread of mankind over a more extensive range than we could have occupied with only the equipment of our own bodies. <5>

Eventually man learned to obtain prosthetic insulation without killing the animal source - by shearing wool, spinning it into yarn, and weaving or knitting it into garments. More recently it even became possible to do the spinning, weaving, and knitting without involving other (contemporary) animals at all, relying on the remains of organisms that lived during the Carboniferous era by using fibers chemically synthesized from coal or petroleum derivatives.

The ecological implications of prosthetics have not been clearly seen by either social scientists or biologists because the concept has seemed so narrowly medical. Yet nature's evolutionary breakthrough may best be understood by viewing it as a shift from (a) selective retention of organic traits on the basis of their adaptive utility to (b) selective retention of prosthetic tools on the basis of their adaptive utility. It was no longer necessary to evolve eyes in the back of the head when a species needed rear vision; a tool could cope with the problem.

Viewing tools as detachable organs, viewing man as the prosthetic species, and viewing man-tool complexes as a new component of ecosystems were perhaps novel ways of looking at familiar things, but they were not really radical departures from conventional evolutionary knowledge. Nature had made comparable evolutionary breakthroughs before; these were known already. The resemblance could be recognized and could be illuminating.

Life had once been confined to the sea. The chemical processes involved in life depend on moisture. Invasion of dry land by living forms could come about only as more or less waterproof skins were evolved that enabled organisms to maintain within themselves a wet "internal environment" even when not immersed in water. By enclosing a bit of the sea within themselves, organisms could escape from the sea. <6> Hundreds of millions of years later (but still scores of millions of years ago) a similar principle was applied again by nature in opening up another new range of niches. When animals had depended largely upon the temperature of their surroundings as the main determinant of the temperature inside their skins, opportunities for animal life remained scarce wherever environmental temperatures rose to tissue-damaging highs, or fell to activity-suppressing lows. The evolution of "warm-blooded" birds and mammals opened new niches in new climates by enclosing within an animal's skin a homeostatically temperate mini-climate.

Man has further extended this enclose-and-control principle of nature, not only with clothing, but also with centrally heated or air-conditioned buildings. If the mini-sea or the mini-climate enclosed within the skin of an organism is ordinarily regarded as part of the organism, rather than part of its habitat, then, broadly speaking, even furnaces, refrigeration units, and thermostats can all be understood as prosthetic devices. They are detachable parts of extended human beings. The walls of our buildings and the shells of our vehicles are (like the Eskimo's fur parka) a kind of prosthetic skin with which we surround our enlarged selves, enclosing mini-environments within them.

When nature spawned man, nature generated a new mode of interaction between organism and habitat. <7> Man would invent new ways of enclosing within his own expanding boundaries those conditions required by his original organic traits. Much of what would happen after nature made the human breakthrough would amount to spontaneous and prolific exploration of the potential of that new mode of interaction between organism and habitat. By the time the Age of Exuberance turned into a post-exuberant age of overpopulation, it was beginning to be possible to see not only the amazing lengths to which the prosthetic nature of man had carried nature's experiment, but also the fact that the enormous potential of the new mode was not without both hazards and limits. <8>

Species of Many Niches

Several years before I happened to see the mirror-wearing cyclist on the highway in North Dakota, I had attended in Boston a meeting of the American Society of Naturalists. The presidential address was given by a California geneticist, G Ledyard Stebbins. <9> His topic was "The Natural History and Evolutionary Future of Mankind". He had looked at the human species in the way naturalists look at other species, raising a more or less standard set of questions about it. Where does man occur, he asked. Everywhere on earth, he answered. Why does man occupy so ubiquitous a niche, he asked. Because he can modify his external environment, he answered. When did he occupy this niche? From many thousand years ago to the present. How? By using tools, organizing himself into societies, and coping with problems by means of deliberative foresight. Man's future, said Stebbins, would depend on improving his capacity for social organization and overcoming his tendency for self-deception; he sometimes pursues attractive but disastrous goals.

It was a thought-provoking address, but I had gone away bothered by his reference to man's niche (singular). As a sociologist, I was trained to be sensitive to the diversity of man's ways, and it seemed to me to make better sense to think of our species as filling many niches.

Especially in modern industrial societies, human life is characterized by a highly ramified division of labor between a vast assortment of occupational specialties. This has had adaptive advantages. If every author had to grow his own wheat and bake his own bread to obtain the strength to mine his own ore and smelt his own iron to make his own typewriter before starting to write, the world would have few typewriters and few books (even on agriculture, baking, mining, or manufacturing). The cliche fits: if people had to be jacks of all trades, they would be masters of none - and there could be only a few trades and comparatively few people.

What happened was that the members of a single species discovered ways to behave almost as if they were many different species. Technology facilitated this useful differentiation of one species into many "quasi-species". A man or woman with one set of tools could do one sort of job (fill one sort of niche), while a person with a different set of tools could do another sort of job (fill another kind of niche).

Long after I heard Professor Stebbins's address, the mirror on the cap of the bicycle tourist gave me closure! It occurred to me that the choice between speaking of one worldwide niche versus speaking of many distinct niches scattered across all parts of the planet simply depended on whether tools were seen as devices that modify habitats to fit them to people, or as detachable modifications of people that fit them to varied habitats.

Highly varied man-tool combinations can live in highly varied environments; that was the fact to which Stebbins had called attention. It could be interpreted two ways, however. From the one-niche perspective, tools could be said to have enabled Homo sapiens to homogenize an otherwise diverse world - making all parts of it available for human habitation. From the multiple-niche perspective, the same tools could be said to have enabled a more or less homogeneous species to diversify itself enough to live in many different kinds of habitat. To a cultural anthropologist or a sociologist, the latter interpretation was more congenial. Homo sapiens remains one species genetically, but by means of diverse sets of artifacts (and diverse customs for using them) this one species has become ecologically diversified. Social scientists carried their insight too far, however, as we now begin to see. They so emphasized the power of mankind to become diversified culturally (including technologically) that they assumed this differentiated Homo sapiens from all other species and made irrelevant the concepts by which we understood the forces affecting other forms of life. Sociologists, impressed with the special humanness of humans, almost lost sight of the mutuality of impact of organism and habitat upon each other. Regaining awareness of the interaction of organism and habitat was a necessary antidote to our self-deceptive tendency, which, as Stebbins pointed out, has enabled our species to pursue some disastrous goals (such as exuberantly overshooting permanent carrying capacity).

All organisms have to adapt; it has always been arguable whether adaptation refers to what the habitat does to the organism, or what the organism does to the habitat. Always the effect is really mutual. As we saw in the last section of Chapter 7, recognition of the mutuality of the effect is the distinctively ecological insight that has been so difficult for the human mind, after an Age of Exuberance, to keep in focus.

Adaptation means something has been modified to "fit" or "go with" something else. I had seen the mirror on the cyclist's cap as a modification (extension) of his visual organs, not as a modification of his environment. In the same way we could see flint-scrapers as supplementary teeth or fingernails. Proto-humans with flint scrapers could interact with their environment in ways that other proto-humans with only natural teeth and fingernails could not. After thousands of generations, these most primitive tools would be superseded by more sophisticated supplementary organs. The pocketknife I have carried since I was in grade school, for example, excelled the flint scraper's utility by as much as that stone tool had excelled nature's tooth and claw.

Not only would man devise artifacts that could do better the things his own organs might have done crudely; he would also devise them to do things he could not otherwise have done at all. Just as we did not have to evolve eyes in the backs of our heads when the need arose to see behind us, we did not need to evolve feathered forelimbs in order to fly. Most of us easily took up the habit of assuming that we fly by "getting into" an airplane. But when an airline pilot with thirty-three years of flying experience refers to the familiar act of buckling his cockpit seatbelt as "strapping a DC-8 to my waist", it is clear that even a modern jetliner can be seen as an elaborate prosthetic device. From the one-niche perspective, we might have thought of it as a tool for modifying the thin upper atmosphere to make it inhabitable by surface-dwelling man. Wings speeding through thin air make it "solid" enough to support the passengers' weight, and the cabin pressurizing pumps make it dense enough for them to breathe. From the multi-niche perspective, the airplane is a set of prosthetic wings and lungs that people "put on" when they have occasion to fly into an environment for which they were not genetically prepared.

Looking at matters this way, it was not just Neil Armstrong who in 1969 took the "short step for a man" down from the modified environment within the lunar landing craft onto the moon's inhospitable surface. It was a fantastic man-tool combination (astronaut clad in spacesuit with life support pack) that took the "giant step for mankind". By the enclose-and-control principle, this man-tool combination was recapitulating the experience of the sea-bred creature that first made a go of it on land.

Altered Carrying Capacity

Two million years after his ancestors learned to walk upright, Homo sapiens (with tools par excellence) had left footprints on the moon. He had also learned to fly in bunches of three or four hundred to business conferences on the far side of a continent, or to holidays on the far side of an ocean, by strapping on a DC-10 or a Boeing 747.

If people in the post-exuberant world could really become accustomed to thinking of even a jumbo jet as an enormous prosthetic device, a detachable organ, perhaps they could then make headway toward understanding the real ecological nature of the predicament our species had got itself into.

As we have seen, Homo sapiens made a breakthrough ten thousand years ago that enlarged (for the time being) the carrying capacity of his habitat. He learned to plant seeds and manage the growth of vegetable matter for his own sustenance, rather than leaving it to untended nature. As his horticultural endeavors progressed, advancement had to include improved methods of cultivating the soil. The simple digging stick was superseded by the hoe and eventually by the ox-drawn wooden plow. Only one hundred centuries after agriculture began, the digging process was accomplished in the most "advanced" nations by steel plows propelled by tractors that burned fossil fuel.

In those same societies, Homo sapiens had in the meantime discovered other reasons for digging into the earth's surface. Besides wanting to plant seeds, people now wanted to extract from below the surface vast quantities of non-renewable resources such as coal. If the digging stick was a prosthetic device, so was the modern power shovel, however enormous it might have become. Modern man's dependence on the ghost acreage of fossil fuels was so great that his power shovels became incredibly huge. A Kentucky lawyer, writing in The Atlantic Monthly of September, 1973, described industrial man as "the greatest geological calamity to hit the world since the melting of the ice sheets". He portrayed one of the mining devices operated by the Central Ohio Coal Company. The machine stood twenty stories high, he said. It used five-inch steel cable to lift a boom 310 feet long. With each bite into the earth it could remove 325 tons of "overburden" to permit "recovery" of coal underneath. <10>

From the time when the evolutionary breakthrough by nature brought forth the human way of evolving, the carrying capacity of man's habitat has never been fixed. Ever since man became human by making himself dependent on tool use, his dependence has consisted increasingly of the fact that he occupied niches made possible by his tools - niches that were previously nonexistent. In broadest terms, then, the function of technology has been to enlarge the human carrying capacity of any habitat. From dugout canoe to jet clipper, and from digging stick to giant power shovel, technology had enabled human beings to go places they could not otherwise reach, and to use substances they could not otherwise have exploited. Without the technology to make them usable, many substances in man's environment would not have become "resources".

Too Much of a Good Thing

Technological progress went beyond facilitating the takeover method of carrying capacity expansion. It led to our commitment to the self-destructive drawdown method. It facilitated useful quasi-speciation, but it also fostered excessive quasi-speciation, as we shall see in a moment. Nothing inherent in tools guaranteed that they would always be used in positively adaptive ways. The capacity for self-deception mentioned by Stebbins was important. Tools could be misused, and tool-using could also lead to an overwhelming "success" that would be tantamount to failure.

Consider misuse first. Take as an example the fire-making and fire-using tools that were from the outset an important part of human technology. These tools helped mankind multiply and spread into new niches. They extended the list of organic substances people could use as food. They extended the list of inorganic substances they could use for making other tools. They supplemented the heat-generating ability of a warm-blooded, mammalian body. <11> Eventually they became sophisticated enough to give access to that temporary carrying capacity buried as ghost acreage in the Carboniferous period. But always there was the possibility of accidental or deliberate misuse of fire. Fire could injure. Fire could destroy tools; it could destroy crops; it could destroy forests people thought they were not using (because they had not learned to recognize the indirect ways in which such "unused" lands served them). After a human-caused forest fire, with water-retention capacity lost in the denuded area, erosion could result that would destroy the crop-growing potential of lands people did know they were using.

But consider also the fact that essentially symbiotic (and even predatory and parasitic) relations were generated among human beings when their tool-using cultures enabled them to differentiate into many interacting "quasi-species". Another form of misuse arose and became common as a result of this. Each person's welfare no longer depended simply on what he could himself harvest from soil and water. It now depended on what he could obtain by exchange, from other human beings differently specialized. Whatever product or service one's own specialized efforts produced, it was unlikely one could subsist on it alone. A person had to obtain from others fulfillment of some of his own needs, and provide fulfillment for some of theirs. That was a basic aspect of being human. Because of the exchange relationship generated by this aspect of humanness, human beings came to be defined as resources. When humans defined humans as resources, misuse became probable.

In nature it was normal for one species to be a resource to another. Lions ate zebras not because lions were vicious, but because lions were lions (and zebras were edible). Man, the prosthetic species, was capable of (or subject to) quasi-speciation as different men used different tools. As a result, men would exploit (use) other men simply because men were men (and other men were different).

Homo sapiens was a species that could enlarge the carrying capacity of its own habitat by using tools. This ability meant that human beings would increasingly discover ways of using as tools things that had not been tools originally - including other human beings. Just as a non-lactating mother could use a cow to provide milk for her child, or a blind person could use a dog to lead him about, so one human being could use another human being's skills. <12>

One organism can be a prosthetic device to another. Being socially differentiated, a human population could be prosthetic to one another, although humans were never merely prosthetic devices. Cows and dogs generally acquiesced in their tool roles, but humans might not. If it was natural for humans to function as tools, it was also natural for human tools to assert non-tool aspects of their humanity. Inherent in man's capacity for quasi-speciation, therefore, was a source of chronic tensions. Prosthetic differentiation of the human species was a cause of human woe far more deeply endemic than either the "contradictions" Marxists supposed were specific to capitalism, or the aggressive and deceitful tendencies "free world" leaders supposed were specific to authoritarian regimes.

The very aspect of human nature that enabled Homo sapiens to become the dominant species in all of nature was also what made human dominance precarious at best, and perhaps inexorably self-defeating. Although man could not be human without quasi-speciation, perhaps with it he could neither avoid habitat destruction nor remain humane.

Which brings us back to the problem that success can lead to failure. Mankind extended to an unprecedented scope nature's principle that niches can be multiplied by the technique of enclose-and-control. Human beings became enormously numerous by using a vast assortment of detachable organs, many of them fantastically complicated and prodigiously large. An almost incredibly large fraction of the biosphere was thus enclosed and controlled by man-tool systems. This situation had to bring our species up against the influence of limiting factors. Belief in the illusion of limitlessness could not protect us; in fact, it probably hastened our encounter with nature's limits by hastening drawdown.

For all organisms, the necessity of maintaining some constancy of conditions inside the system has required the existence of an "outside". Maintenance of constancy within the system involves processes of importing and exporting materials and energy - to compensate for changes that would otherwise happen inside the organism's boundaries. Life has always depended on opportunities for living systems to obtain "resources" from their environment, and to exhaust spent substances (with autotoxic properties) into the environment. So the advantage to be gained by enclosing a piece of the environment within the system has always depended on there being plenty of environment left outside. Too many systems too much enlarged vitiate this advantage by seriously diminishing the environment/system ratio. (To those who use the word "exploitation" politically rather than ecologically, the importance of all this remains invisible.)

Homo sapiens has exploited too much. Human "success" entailed enclosure of an unprecedentedly large fraction of the total environment within the expanding boundaries of proliferating man-tool systems. There was consequently less "outside" in proportion to "inside" than had ever before been the case. The ironic result was that technology, which originally had been a means of increasing the human carrying capacity per acre of space or per ton of substance, became instead a means of increasing the space required per human occupant and the substance required per human consumer.

Post-exuberant man found himself playing a game with changed rules. It was no longer uniformly true that additions to technology added to his habitat's carrying capacity. At 500 miles per hour it took fewer planes than at 150 miles per hour to make the airways crowded. At 325 tons per bite, it took fewer digging operations than with a digging stick to devastate the countryside.

Man used to live in a world where carrying capacity was equal to the product: resources times technology. Man's "success" changed it into a world in which carrying capacity was coming to equal the quotient: resources divided by technology. The predicament of mankind no longer consisted merely of the simple Malthusian problem of an expanding population pressing against fixed limits of a finite habitat (or against less rapidly rising limits of a stretchable habitat). Now it was a worse predicament - an expanding population with burgeoning technological power was shrinking the carrying capacity of its habitat.

The human community was undergoing succession as a direct consequence of man's nature as a prosthetic or tool-using species. The more potent human technology became, the more man turned into a colossus. Each human colossus required more resources and more space than each pre-colossal human. Contrast the environmental impact of the Central Ohio Coal Company and its huge machines with the environmental impact of the Stone Age people who inhabited the same area a few centuries before. <13> The Indians had not necessarily possessed any more virtue; they simply used cruder tools. They were non-colossal.

The same kind of problem would be much easier to recognize if mankind were afflicted with some kind of mutation that had the curious effect of causing children to grow to twice their parents' adult size - so that they required twice as much food and fiber per capita to sustain life and comfort. Suppose, further, that the effect were somehow cumulative, so that each generation grew twice as large and voracious as the preceding one. Quite obviously, the world's carrying capacity would be much less for later generations of giants than for earlier generations of runts. Just as obviously, neither conventional political nostrums nor revolutionary agitation could do much to remedy the situation.

Perhaps we would know this if we ceased to call ourselves Homo sapiens and began to call ourselves Homo colossus. If we were accustomed to thinking of a human being not just as a naked ape or a fallen angel but as a man-tool system, we would have recognized that progress could become a disease. The more colossal man's tool kit became, the larger man became, and the more destructive of his own future.


1. Actually, the visual fields of a rabbit's two eyes do overlap somewhat in front; the rear overlap is not in the horizontal plane, but is somewhat elevated, suggesting that selection pressure from predatory birds may have had more to do with rabbit evolution than threats from surface- dwelling predators. See Austin Hughes, "The Topography of Vision in Mammals of Contrasting Life Style: Comparative Optics and Retinal Organisation", Chapter 11 in Frederick Crescitelli, editor, The Visual System in Vertebrates (Berlin: Springer Verlag, 1977), pages 613-756.

2. Boughey 1975, pages 31-35 (listed among references for Chapter 2). Cf Campbell 1974, pages 84-90.

3. See Campbell 1974, pages 196-202, 234-241; Washburn and Moore 1974, pages 61-82.

4. See Ehrlich, Holm, and Brown 1976 (listed among references for Chapter 2), pages 482-483.

5. Campbell 1974, pages 384-401.

6. This idea was ingeniously developed by Cannon 1932.

7. Kraus 1964, pages 285-288.

8. Compare with each other the following: Cannon 1932, pages 287-306; Campbell 1974, pages 401-408; Montagu 1965, pages 199-213; Sears 1957, pages 45-60; and Salk 1972, pages 53-118.

9. Stebbins 1970.

10. Harry M Caudill, "Farming and Mining: There Is No Land to Spare", The Atlantic Monthly 232 (September, 1973): 85-90.

11. Campbell 1974, pages 241-244.

12. Cf Dice 1955, pages 28-30.

13. Cf Sears 1957, page 21.

Selected References

Campbell, Bernard G. 1974. Human Evolution. 2nd ed. Chicago: Aldine.

Cannon, Walter B. 1932. The Wisdom of the Body. New York: W W Norton.

Crick, Francis. 1966. Of Molecules and Men. Seattle: University of Washington Press.

Dice, Lee R. 1955. Man's Nature and Nature's Man: The Ecology of Human Communities. Ann Arbor: University of Michigan Press.

Dubos, Rene. 1968. So Human an Animal. New York: Charles Scribner's Sons.

Kraus, Bertram S. 1964. The Basis of Human Evolution. New York: Harper & Row.

Montagu, Ashley. 1965. The Human Revolution. New York: Bantam Books.

Salk, Jonas. 1972. Man Unfolding. New York: Harper & Row.

Sears, Paul B. 1957. The Ecology of Man. Eugene: Oregon State System of Higher Education.

Stebbins, G Ledyard. 1970. "The Natural History and Evolutionary Future of Mankind". American Naturalist 104 (March-April): 111-126.

Washburn, S L and Ruth Moore. 1974. Ape into Man: A Study of Human Evolution. Boston: Little, Brown.

Bill Totten


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