Geology Reference
In-Depth Information
Perhaps this course will enhance your understanding of these
areas. Even when you fl y across the United States, it is easy to ob-
serve some of the country's large-scale features, such as moun-
tain ranges, plains, the Mississippi River delta, the Basin and
Range Province, and the vast lava fl ows of the Pacifi c Northwest.
because there had been earlier periods in the Pleistocene when
cold spells had ended and people didn't alter their way of life.
The adoption of farming as a way of life was a momen-
tous change for humans. Farming ties people to a particu-
lar place, thus ending the nomadic lifestyle (
Figure 24.2).
If the crops grow well, farming can produce more food than
any other system that came before it, allowing people to have
at least small amounts of “free time.” With more time, people
learned to throw pots (needed to store grain and liquids such
as olive oil), make simple bricks (ideal for building simple
homes), and weave sturdy baskets (useful at harvest time).
It wasn't long after these specialists appeared in village soci-
ety that systems of writing words and numbers appeared in
human history. Thus, we see that the division of labor made
possible by farming is the foundation of modern society.
Once people were committed to farming, they began
to domesticate large animals and taught them to pull plows.
This dramatically increased the productivity of human
farming efforts. For the fi rst time in our history, it wasn't only
human muscle power that could be put to use for our benefi t.
Animal waste was also a natural fertilizer for farm fi elds.
Although farming brought astounding benefi ts, agriculture
can be highly destructive to the very foundation of farming—
that is, soil. Today, we have more areas of the planet under the
plow than ever before. Erosion and soil degradation make some
farm fi elds infertile, whereas many others are kept in produc-
tion only through the use of artifi cial fertilizers (see Chapter 6).
Sometimes governments step in to promote practices that
conserve soils. In the United States and Canada, farmers have
been subsidized for planting different crops side by side in the
same fi eld, a practice that reduces erosion because the whole fi eld
isn't disturbed at the same time. In some parts of Central Amer-
ica, in contrast, there has been no regulation of agriculture.
Our future as a species is clearly linked to the wise man-
agement of our soil resources. Like other conservation efforts,
using soils sustainably depends on a combination of scientifi c
understanding and political will. Your generation will probably
GEOLOGY, HISTORY, AND
THE AGRICULTURAL REVOLUTION
When most of you were born, probably around 1987, the
estimated world population was 5.0 billion, but now, only
20 years later, the estimate is 6.7 billion and about two-thirds
of this huge number of people live in the 15 most populous
nations (Table 24.1). How is it possible for Earth to support
so many people? Of course, technological innovations and
advances in medicine have played a key role, but none of this
would have been possible if it were not for the Agricultural
Revolution, which was a major shift in human economy
from hunting and gathering to permanent communities that
depend on agriculture. Civilization depends on the soils that
produce the food that sustains the world's population, so, in a
sense, soil is the foundation of our lives and all world cultures.
For most of human history, we and our ancestors were
hunter-gatherers, rather than farmers, depending on hunting
or gathering wild foodstuffs. Hunter-gatherers are nomads,
often on the move, and their lives are generally brief and dif-
fi cult. However, for reasons we do not fully understand, hu-
mans changed their way of living at several places around the
globe between 8000 and 14,000 years ago. Different groups,
separated by vast oceans, came to understand the advan-
tages of agriculture at roughly the same time, near the end of
the most recent cold spell in the Pleistocene Epoch (the Ice
Age). The climate change does not explain this shift, however,
TABLE 24.1
Estimated Population of Earth's 15 Most
Populous Countries for August 2007
Rank
Country
Population*
1.
China
1,321,852,000
2.
India
1,129,866,000
3.
United States
301,140,000
4.
Indonesia
234,694,000
5.
Brazil
190,011,000
6.
Pakistan
169,271,000
7.
Bangladesh
150,448,000
8.
Russia
141,378,000
9.
Nigeria
135,031,000
10.
Japan
127,468,000
11.
Mexico
108,701,000
12.
Philippines
91,077,000
13.
Vietnam
85,262,000
14.
Germany
82,401,000
15.
Egypt
80,265,000
Figure 24.2 The Agricultural Revolution Farming tied people
to a particular location and yielded more food than hunting and
gathering. This image shows farmers in southern Egypt irrigating
their fi eld with water from the Nile River.
*Rounded to the nearest 1000.
Source: http://www.infoplease.com/ipa/A0004391.html
 
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