Animal and Human Energy

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Culture is the primary mechanism of human behavior and adaptation. Cultures are passed on socially from generation to generation. Tools and the ways they are made and used both shape and are shaped by the social organizations of which they are a part. In his classic study, The Science of Culture, Leslie A. White suggested that cultures grow in relation to the degree of efficiency of their tools in liberating energy from their natural environments. A working hypothesis in present day anthropology suggests that, in general, as tools became more efficient and numerous, populations increased in size and density, and new forms of social organization had to develop to cope with these population changes. It would be useful to consider three very general evolutionary stages in the development of our topic: hunting-gathering societies, early agricultural societies, and state agricultural societies.


There is archaeological evidence that the earliest stone tools were used in Africa more than two million years ago. These "pebble tools" were often made from flat, ovoid river stones that fit in the palm of one's hand. Another stone was used to chip off a few adjacent flakes to form a crude edge. However crude the edge, it could cut through the thick hide of a hunted or scavenged mammal when fingernails and teeth could not, and thus provide the group with several dozen to several hundred pounds of meat—a caloric and protein windfall. It is a common misconception that stone tools are crude and dull. Human ancestors learned to chip tools from silicon-based stones such as flint and obsidian that have a glass-like fracture. Tools made from such stones are harder and sharper than finely-honed knives of tool steel. As early as 500,000 years ago, well-made hand axes were being used in Africa, Europe and Asia. There is evidence that people were using fire as early as one million years ago. With the advent of the use of fire, it is believed that the amount of energy used by early man doubled from 2,000 kilocalories per person per day (energy from food) to about 4,000 kilocalories per person per day (Figure 1). Thus, fire and eventually the apparatus employed to make it were important energy liberating tools. Cooking food allowed humans to expand their diet. Controlled fire could also be used to scare game into the open to be hunted. Present-day hunters and gatherers burn berry patches in a controlled way, to encourage new plants and more berries. Fire also subsidized body heat, allowing people to colonize colder regions.

The Neanderthal people who lived from about 130,000 to 35,000 years ago invented gracile and efficient "blade tools" that allowed them to make lighter and sharper spearheads. The Upper Paleolithic hunters who succeeded the Neanderthals made many smaller, lighter, and super-efficient blade tools called burins, each of which could be used for a special purpose. These burins could be transported easily from campsite, thus saving energy. Upper Paleolithic hunters also made many small and efficient tools from bone, ivory, shell and wood. The Upper Paleolithic invention of the atlatl or "throwing stick" allowed hunters to throw spears and darts at animals over longer distances and with greater force and accuracy than comparable missiles thrown by hand.

Just at the end of the Upper Paleolithic a Mesolithic cultural period emerged and with it several new innovations made hunting even more energy efficient. The bow could launch very lightweight arrows at game, and poison for arrows decreased the time spent stalking wounded prey. Finally, the domestication of the dog, itself a master hunter, lightened the hunter's task.

Anthropological research with modern hunter-gatherers suggests an ideal type or model for this kind of society. They were nomadic and exhibited low population size and density—on the order of thirty people per thousand square miles. Paramount in maintaining this low size and density was an imperative common to all hunter-gatherer women. A nomad woman had to move herself, all that her family owned (which was very little), and her children at a moments notice. Modern hunters and gatherers often have to walk twenty miles a day, so mothers cannot carry more than one small child. Faced with this restriction, women are careful to space their children so that the two or rarely three children they have will not burden them when they must move. There is every reason to believe that this pattern also existed in remote times.

There was little social differentiation. No one was particularly rich or poor. Leadership was informal and transitory and based on cooperation and sharing, especially with regard to meat. Although homicide was known, intragroup conflict was usually resolved by breaking the group into two or more subgroups that avoided each other until the conflict was resolved or forgotten.

Warfare was not a major cultural focus of hunter-gatherer communities and most anthropologists are of the opinion that when it did occur it was due to population pressure exerted by agricultural and/or state societies. Although hunter-gatherer social structure was informal and free-form, it was efficient with regard to hunting big animals. Studies of modern hunter-gatherer societies indicate that very little work is done in many such groups. With some exceptions, hunter-gatherers worked approximately four hours per day per adult.


Beginning about eleven thousand years ago in the Middle East and somewhat later in other parts of the world, people began to experiment with the more sedentary subsistence patterns of growing crops and animal husbandry, and thus the Neolithic revolution began. Scholars cite two reasons for this change. First, the last glacial period began to wane as did many of the big mammals associated with it. Second, hunter-gatherer tools and organization became so efficient that human population numbers became relatively large and depleted the supply of game and wild food plants. Population expansion resulted in competition for space and directed humans toward the invention of more intensive modes of food production.

Early Neolithic peoples domesticated the more productive local plants, cared for them in densely planted plots, protected them from animals and other plants (weeds) and harvested the results. Likewise they tamed, bred and cared for local animals and ate them as they deemed fit. In the cases of cattle, horses, sheep and goats, milk and its products became staple foods. In some places larger domestic animals became beasts of burden. For very sound ecological reasons, agriculture allowed even early farmers to liberate much more caloric energy from plants than could be liberated from hunting and gathering and, thus, many more humans could be supported per square mile. In ecosystems, the most numerous organisms (measured in mass) are plants. Animals that eat plants (herbivores) are less abundant, while animals that hunt and eat these herbivores are least numerous. The reason for this decrease in "biomass" as one proceeds up the food chain lies in the fact that there is a considerable loss of energy due to inefficiency as animals search out, eat, digest and change the plants they consume into heat, growth and kinetic energy. The same can be said with regard to the killing and utilization of herbivores by hunting carnivores. Thus when people began cultivating plants, in effect, they stopped being carnivores and became herbivores and their population size and density increased. Since agricultural peoples were sedentary, they lived in more or less permanent settlements and their women could and did have more children. In early agricultural societies the amount of energy liberated per person per day rose to about 11,000 kilocalories.

In woodland areas early farmers developed swidden agriculture. They cut down forest plots using new and more efficient axes that were ground and polished from hard and dense stone. The plots were left to dry and then were burned, allowing nutrients to return to the soil. One to three plantings could be grown on these plots every year. Other plots were then prepared and cropped until the original plot had been overgrown and the process was repeated. Swidden cycles lasted from about thirty to one hundred years.

In general there is a correlation between human population size and complexity of social organization. In the 1960s, Robert Carneiro showed that there is a rough positive correlation between the number of organizational traits (N) in single community societies and their population (P), expressed by the equation . Neolithic populations increased and there was an organizational reaction. Society became stratified based on access to the extra calories of agricultural surplus. It was now possible for some people to "own" more land and animals than other people. With sedentary lifeways it was possible to accrue and own duplicate things and heavy things. Coercive institutions like war evolved to protect what one had and as the means to get more. Although more work was done in early agricultural societies, the people in these societies probably had, on the whole, more leisure time than people today. The cultural florescence of the Iroquois Indians of New York State is a case in point. Around 1000 C.E. a Proto-Iroquoian culture became evident in the archaeological record. This Owasco culture was characterized primarily by swidden agriculture of maize, beans and squash supplemented by hunting and gathering. Over the next six hundred years village size increased as did size of dwellings. Villages became palisaded and cannibalism became evident, indicating that warfare was an institution of growing importance. When Europeans began to establish contact with the Iroquois in the 1600s, they found a people with sufficient leisure to engage in elaborate warfare patterns that were connected with a rich and complex ritual life. At first contact the Iroquois were building advanced political and governmental institutions and establishing larger orbits of political influence based on the collection of tribute.


Late Neolithic times saw the evolution of a technical innovation that fostered the growth of societies that were monumental both in population size and organization. This innovation was irrigation. Hence, historians such as Karl Wittfogel speak of the "hydraulic" theory of the state. In Old World societies like Egypt, Mesopotamia and Northern China, farmers began to grow crops on the flood plains of great river systems, taking advantage of the water and nutrients that these rivers deposited on an annual basis. Irrigation works and the subsequent population increase they stimulated required more irrigation and an evolving bureaucratic organization to manage workers, works and increasing surpluses. The animal-drawn plow became very important at this juncture and thus there was a dramatic rise in the calories that farmers could wrest from their environments. A man pushing a lever could generate about 1/20 horsepower, while an ox pulling a load (or plow) could generate 1/2 horsepower. This new technology could support still larger populations than could simple agriculture. The large-scale civilizations which evolved in all three areas supported hundreds of people per square mile. Similar state societies based on irrigation evolved independently in the New World even though Conquest States like the Aztecs and the Incas of Peru lacked both the plow and the wheel and had no beasts of burden except the dog and the llama.

Modern State Societies depend on irrigation farming as well as dry field agriculture based on mechanized energy subsidies. At first steam power accounted for these subsidies. By 1800 Watt's steam engine could generate 40 horsepower. Later the internal combustion engine replaced steam. At the height of the Industrial Revolution (c.1850) each person used about 70,000 kilocalories per day. Today we have entered into a new phase of social ecology subsidized by an ever-increasing use of fossil fuels. As a result people in developed countries now use about 140,000 kilocalories per person per day.

David Mulcahy


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