The Pleistocene Period was a time of hunting and gathering, experimenting with tools, and traveling in the direction of edible plants and animals. The ability to adapt to changing environments and resources was their most important survival mechanism. Evidence has shown that approximately 10,000 years ago, agriculture was being practiced. Archaeologists suggest that plant domestication began because of rising populations and changes in exploitation of local resources. Human consumption and being constantly in contact with plants then gradually brought about plant domestication. Because of agriculture's ability to provide a stable and large quantity of produce, population densities then grew even more.
Plants became a major factor during this period as well. The first cultivation of plants began during this time span. The plants which were first cultivated were weed plants, such as Lambs Quarters and Marsh Elder. Many of these plants were cultivated by stone and bone tools. The cultivation of Sunflowers also developed during this time span. Sunflowers were the plants most often grown following the Archaic period. The domestication of small animals such as dogs also happened during this time.
In Mesoamerica five or more plant species were well
on their way to being domesticated a few thousand years before the first
permanent communities appeared. Maize first appears in southern Mexico about
7000 years ago. Also beans, squash, pumpkins and peppers have been found.
Initial domestication began after 8000 B.C., perhaps accidentally.
Maize was a main staple and the plant of which
significant evolutionary history has been studied. It was first thought to have
evolved from a wild maize that had small cobs and tassels growing out of it.
Then in the 1960's
Richard
MacNeish was excavating a site near Tehuacan, Mexico and found remains of
this so called wild maize. He realized it looked very similar to another wild
grass common to this semi arid, sub temperate area of Mesoamerica, called,
Teosinte. Later George Beadle, a plant geneticist argued that maize was
descended from Teosinte. It is still found in subtropical regions of Mexico and
Guatemala and grows easily in old cornfields, often found with beans and
squash. Corn, beans and squash are still grown together today. The beans grow
up the corn stalk and the squash provides protective ground cover.
If Teosinte is the true ancestor of corn today then according to Robert Wenke, the important adaptations in the domestication process were, 1)"the development of a less brittle rachis, followed by the evolution of the cob; 2) the development of a soft fruit case, so the kernels could be shelled free of the cob; 3) the evolution of larger cobs and more rows of kernels" (Wenke:270).
In Tehuacan, around 5000 B.C. the average cob size was about 2 centimeters and by 3400-2300 B.C. they were 4.3 cm. Not until 700 A.D.- 1536 did they reach averages of 13 cm. Beans were also being domesticated at the same time as corn. Nutritionally beans provided lysine, something corn lacked and humans needed for a healthy diet. Domesticated beans don't appear until 4000-3000 B.C. The changes it underwent include, 1)"increased seed permeability, so that beans need not be soaked so long in water before being processed; 2) a change from a corkscrew shaped, brittle pod that shatters easily, to straight, limp, non-shattering pods and; 3) in some cases a shift from perennial to annual growth patterns. Little is known today about the evolution of squash or pumpkin" (Wenke:315).
Wenke, J Robert. Patterns in Prehistory- Mankind's First Three Million Years. New York. Oxford University Press 1980, 267-327.
