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Biology 103
2000 Third Web Report
On Serendip

The Origins of Agriculture

Rise of Civilization or Defying Evolution?

Promise Partner

Think back to junior high social studies...Before the Fertile Crescent, everything was dark. Only with agriculture did humans really become humans. We lifted ourselves out of the savage life of foraging: living in caves, searching for food from dawn until dusk, chasing beasts or being chased by them, always hungry and worried where we would find our next meal. We could now devote our abundant free time and energy to erecting great cities, creating art and literature, musing about gods. Agriculture is the defining characteristic of humans and all our achievements followed this one. By controlling and containing our food source, civilization began.

Did it really? The traditional paradigm of agriculture depicts it as superior to a more primitive lifestyle of hunter-gatherers. Domesticating crops is seen to be the more evolutionarily advanced form of food production. Today agriculture supports nearly all humans and most of the arable land on earth is cultivated. However, recent studies have shown that hunter-gatherers were highly successful evolutionarily and healthier biologically, and, some argue, socially happier than early farming communities. What prompted us to abandon the lifestyle we had practiced for 90,000 years, especially if it was more advantageous than the one we replaced it with?

The theory of cultural invention assumes that once bioculturally capable, humans would inevitably develop agriculture, giving up animal-like methods and following the evolutionary process to more complex system. This theory assumes that to become agriculturists, people need to develop enough understanding of plants and animals or they must stumble upon this knowledge. However, foragers had advanced knowledge of their food sources, in some cases practicing cultivation, irrigation, periodic burning, and other manipulations. Exposure to agriculture did not always mean conversion; some groups of foragers lived nearby agricultural communities yet continued to practice hunter-gathering (1).

A social model of agriculture, "competitive feasting," explains the change through societal interactions. In circumstances of "high food stress," foragers made alliances based on food sharing to prevent the depletion of resources. In rich areas of undepletable resources, however, sedentary societies formed and opportunities for competition increased. Thus agriculture developed to produce more food for the growing number of humans and their increasing competition for resources (2).

Many explanations link the origins of agriculture with changes in the global environment. The "oasis theory" proposes that after the Pleistocene era, the last great glacial advance that ended about 12,000 years ago, a major period of desiccation occurred. Humans and animals sought refuge in oases that could support them, like the Fertile Crescent in Mesopotamia. The availability of potential domesticates resulted in the practice of agriculture, and thus settled communities and increasing populations (2). The proximity of protodomesticates may have caused coevolution, the mutual evolving of two interacting species. As humans modified the domesticates' environment, they created genetic changes that made the plant reproduce better in the altered environment. These same changes made the domesticates more attractive to humans, who would modify their behavior to favor the plant, increasing their food supply and thus their offspring (1).

Another idea proposes that the long, dry seasons occurring after the Pleistocene caused adaptations in vegetation. The conditions supported annual plants that left dormant seeds or tubers. The abundance of these readily storable wild plants allowed for the first settled villages. For example, in the Fertile Crescent the first crop were edible seeds, wheat, barley, peas, lentils, chickpeas, bitter vetch, and flax, all which were easy to grow and to store, grew quickly, and had to undergo few genetic changes to be useful (3).

Changing levels of atmospheric carbon dioxide, affecting plant photosynthesis, also may have created an environment supportive of agriculture. During the Pleistocene, CO2 levels were below 200 parts per million, increasing to above 250 ppm as the earth pulled out of the glacial age. This may have increased plant productivity by up to fifty percent, enabling crop domestication to develop (4).

Other environmental changes at the end of the Pleistocene are credited with stimulating the rise of agriculture, including the extinction of many species, warming climates, increased seasonality, and rising sea levels. Supporters argue that in order for agriculture to impact various areas independently, it must have been catalyzed by environmental changes (4). However, major climate changes had occurred at other times in the Pleistocene and agriculture arose independently in other eras in places like the Americas (1).

Environmental changes are believed to have prompted agriculture which subsequently increased human population. Other theories propose that it was population increases which lead to agriculture. Population growth over the capacity of the environment forced humans to develop new food production strategies. Agriculture could provide more food per unit of land, though it required more energy. When humans farmed at high population densities, crops were not as subject to overexploitation, whereas increased hunting and gathering in one area could rapidly lead to depletion. "Settled agriculturists can survive at higher population densities estimated to be ten to one hundred times greater than hunters-gatherers" (3). Efficient foraging also depended on mobility, while larger populations were more stationary and thus required a stable food source (1). Therefore as populations increased, humans had to develop agriculture in order to support their growing numbers.

An alternative hypothesis discusses the pharmacological properties of cereals to support humans' transition from foraging to agriculture. The diet of pre-agricultural humans did not include cereals in any quantity. Consumption of cereal seed only increased toward the end of the Pleistocene, and humans did not develop the storage pits and tools necessary for significant consumption of cereals until the Neolithic era. Today, most humans receive two-thirds of their protein and calorie intake for cereal-derived foods like wheat, corn, rice, and barley. The cereals central to early agricultural communities and to our modern diet contain drug-like substances called exorphins. Evidence suggests that ingestion of cereals, unlike foods common before agriculture, "activates reward centers in the brain" and create feelings of motivation, reduction of anxiety, sense of well-being, even addiction. This chemical reward could have been the incentive for adopting agriculture (5).

According to this theory, climactic change at the end of the glacial period increased the size and concentration of patches of wild cereals. Humans who relied on them as food sources discovered their rewarding properties and were attracted to settling around them and abandoning their nomadic lifestyle. They developed methods of processing the cereals, causing increased consumption and further reliance on their drug-like properties. Because evidence suggests that health declined with the adoption of agriculture, rapid replacement of other foods must have been due more to chemical rewards than nutritional reasons (5).

This hypothesis is the only one of the many discussed that directly addresses the evidence that foragers were better off than early agriculturists. The change to farming is assumed to create a better quality of life, especially as we look back on it from our standpoint in the year 2000. However, various evidence suggests that humans were far better off as foragers than after they took up agriculture. Hunter-gatherers enjoyed a varied diet of thousands of types of plants, seeds, fruits, and nuts, while agriculturists relied on just one or two starchy crops, choosing "cheap calories at the cost of poor nutrition." Today wheat, corn, and rice provide most of the calories for humans, yet each one is deficient in certain essential proteins and amino acids. Agriculturists also ran a much greater risk of starvation by depending on a few key crops, as opposed to foragers whose consumption does not rely on any one plant but is diverse and flexible. Agriculture, able to support higher population densities, caused people to live in closer quarters. This invited the spread of parasites and infectious diseases that foragers avoided by living in smaller numbers in larger areas. Studies of various skeletal evidence indicate an increase in infectious diseases, malnutrition, and anemia in early agricultural societies as compared to hunter-gatherers (6).

If agriculture did not make humans healthier, why is it now nearly the sole form of food production on earth? Though evidence shows that early agricultural communities were less healthy than their foraging counterparts, with today's technology we are now certainly healthier than any hunter-gatherer community of the Neolithic age. Have we overcome the natural consequences of agriculture through increasing development of technology? Have we been defying evolution for 10,000 years?

If evolutionary success hinges on the population of species, agriculture was extremely successful, as it caused the rapid increase of human numbers all over the earth. The question of population concerning the proliferation of agriculture is a self-perpetuating cycle. As populations increase, agriculture is needed to produce greater amounts of food. As food production increases through agriculture, populations grow and the demand for food become still greater. Will there be a point when the population is greater that the food capacity? Famines, occurring all over the world, certainly indicate that this is already happening.

Perhaps human are more concerned with expedience and once presented with means that seem to be quicker and more productive will never return to previous lifestyles now deemed difficult and unrewarding. Agriculture gave us more food and made that food controlled and immediate. We never went back. This concern for quantity and quickness continues with modern advances like transportation and computer technology. Who would return to the days when you had to search through almanacs for an afternoon to research a paper? You had to wait for weeks for a letter to be delivered? It took months to travel across the country? We are continually developing ways to make our lives quicker and presumably more comfortable.

Before agriculture it seems that the impetus for evolution was external or environmental. The most popular case, of course, was the meteor that killed off species including the dinosaurs. Agriculture itself undoubtedly arose in some connection with global environmental changes. But since agriculture it seemed that humans have created evolution themselves, their actions destroying species and causing adaptations. Perhaps most importantly the civilizations that have arisen due to the advent of agriculture are now altering the global climate. Maybe we have come full circle and since we have taken evolution into our own hands, we will be our own destroyers.

WWW Sources

1)Origins of Agriculture, the outline of a University of Washington lecture

2)Theories about the Origins and Spread of Farming, presents several main models explaining the origins of agriculture

3)Agriculture: Origins, an explanation from the organization "Primal Seeds"

4)Origins of Agriculture, an article summarizing Rowan Sage's theory linking the emergence of agriculture to an increase in carbon dioxide levels

5)The Origins of Agriculture: A Biological Perspective and a New Hypothesis, a theory by Greg Wadley and Angus Martin associating agricultural development to the drug-like properties of cereals

6)The Worst Mistake in the History of the Human Race, an essay by Jared Diamond refuting the popular idea that agriculture made the human race more successful




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