In contrast to hunting and gathering as a way of life, agriculture implies modifying the environment in order to exploit it more effectively. Both the animals and plants can be modified as a result of human intervention -- domestication. Ultimately, agriculture changes the very landscape itself. The central question is why did agriculture arise in the first place. You may wish to read the following: Why did Agricultural Begin? by Paul Gepts to explore some reasons.
The growing of a single crop in a field by definition substitutes a biological monoculture for the complex ecological system that existed on the same ground previously. This change has several effects. The quantity of food is greatly increased. There are cost to this strategy. Over a relatively short period of time, growing a single crop can deplete even very rich soils. This was a problem which rendered many early agricultural sites uninhabitable after a time. It is still a very serious problem.
There are other unintended effects of crop-growing. The human farmers are consciously altering the environment and "selecting for" the plants they need. Unwittingly, they are also "selecting for" any organism that can live on wheat for example: wheat-eating "vermin," pathogens, and diseases of wheat, etc. Thus, paradoxically, by increasing their food supply, farmers simultaneously increased threats to their food supply. Farming may also create a biological system that lacks flexibility to resist disease or climatic changes. The Great Potato famine in Europe is a classic case. Andean farmers grew a wide variety of potatoes in an effort to maintain diversity as a result of the familiarity with the domesticated potato knowing the various risks associated with it. Farming can also lead to soil degradation and erosion.
The Process of Domestication
Agriculture is a process. One begins with a high
degree of familiarity with wild plant foods. Through a process of experimentation
and ultimately manipulation, humans create a "selective force"
choosing those charactistics they find most favorable about a plant or animal.
The act of harvesting the wild grains changed them genetically in this process.
For example, a small percentage of wild grass plants has
seed that clings to the stalk even when ripe, rather than separating easily.
Humans collecting wheat or barley seed such as these would succeed in gathering
a disproportionate amount of the mutant seeds-that-cling in each harvest.
Thus, the seed they sowed--the act of manipulating--the next year would
gradually increase the amount of seeds-that-cling in the next crop. Over
time, the percentage of wheat and barley seed that falls off the stalk when
ripe declined--which made harvesting much easier. In this way, these crops
were "domesticated" to the point where they cannot reproduce themselves
without human intervention. This is the hallmark of what it means to be
"domesticated"--dependent upon human intervention. Other qualities,
such as the size and number of the kernals, also changed over time, due
to human activities. Lets see how this works with a plant known as agave--not
a traditional agricultural product but one which was manipulated and domesticated
by farmers in prehistoric Arizona: the story of agave.
Other Domesticated Plants from the Americas
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