|The importance of agriculture
Agriculture removed much of the uncertainty in obtaining food. People no
longer had to search it out over large areas—they found places where it
could be produced in abundant quantities year after year and fixed
themselves there. Instead of relying on the environment’s natural
bounty, they could direct and manipulate the provision of that bounty.
Abundant and dependable food supplies allowed population to grow and set
the stage for the rise of civilization.
The human population on Earth two million years ago has
been estimated at 100,000. At the beginning of the agricultural revolution
this number had risen to perhaps five million, thanks to better
adaptation, technology, and abundant resources that became available as
the ice sheets receded. By 3000 BC, the time of the first Egyptian
dynasty, world population had increased to approximately 100 million. By
the birth of Christ, world population was well over 200 million.
The beginnings of agriculture
Agriculture was a gradual discovery. It is believed that early gatherers
first learned the relationship between plants, the foods they produced,
and their growing cycle. At some point the gatherers learned how to
encourage the plants they depended on and inhibit those of no use. Then
came the steps of gathering seeds, planting seeds, and nurturing the
plants. By selecting seeds from the strongest and most productive plants
for replanting, the early planters interrupted and redirected the process
of natural selection to improve the yield of the useful plants. For
example, researchers in Mexico have found evidence of the ancient corn
plant with only a few kernels that became the much more productive corn
plant of ancient America through selection over many thousands of years.
The first domesticated grain is believed to have been a wild wheat that
grew in southern Turkey. To domesticate this plant, the early gatherers
had to learn how to harvest the grain seeds, extract the wheat kernel,
grind it, and bake it, all before they learned how to grow the plant and
select it so that it increased in kernel size. This was a complicated
learning process that took time. Less is known about how and when the rice
plant was domesticated, but it was clearly as important in Asia as wheat
was in the Middle East and corn in America.
The agricultural revolution accelerated as innovations increased arable
land, crop yields, and farmer productivity. Land was cleared by grazing or
fire. Soil was prepared by digging first, and then plowing. Irrigation
insured adequate water. Fertilization and crop rotation increased yields.
Specific tools like the sickle, scythe, plow, and hoe increased farmer
Domestication of animals
Dogs were domesticated from wolves perhaps 15,000 years ago in both
America and the Near East, but dogs were useful mainly as companions,
guards, and hunting aids. The first domesticated food producing animal was
probably the goat, a source of meat, milk, and waterproof hides. This
breakthrough occurred in the hills of modern Iraq. Domestication of the
goat was followed by sheep (meat and wool), cattle (meat, milk, hides,
power), horses (meat, milk, transport), pigs (meat and fat), chickens
(meat and eggs), and others.
Cattle are considered the most significant domestication. In addition to
providing meat, milk, and hides, they were also valuable as beasts of
burden. They pulled wagons, greatly improving land transport. They pulled
plows, greatly improving agriculture. The existence of domesticated cattle
is thought to have been primarily responsible for the doubling of
population in the Near East between 4000 and 5000 BC.
The process of domestication must have been to obtain young animals, raise
them in captivity over enough generations so that they grew less wild and
more tolerant of being managed. It is unclear why some animals could be
domesticated but not others. Why the cow but not the buffalo? Predators
would be unlikely choices for domestication, but the wolf was a predator
and so was the cat, which was domesticated much later.
Domestication of animals brought many important advantages. They were
dependable sources of meat. Cattle and goats converted grass, of little
use to humans, into milk and milk products like cheese. Vast grasslands
that could previously support only a few hunters could now support much
larger populations of herders. Sheep and vicunas produced wool each year.
Animals could graze on broken lands of little use for farming.
Horses, oxen, llamas, and other animals provided power for pulling,
plowing, and carrying. Military uses were eventually found for onagers,
asses, and horses, and to some extent, elephants, although elephants are
not considered domesticated. The horse was domesticated first in the north
Asian steppes and its use spread from there, probably in the wake of Asian
migrations to the south and west. Paleontologists believe the horse
evolved in the Americas actually, but went extinct there, perhaps due to
Mounted Asian barbarians are thought to have overrun the first towns
rising in Asia Minor and the Middle East around 6000 BC. The people that
were overrun may not have seen a domestic horse previously, much less one
on which a warrior could ride.