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CHAPTER 15 • Humans and Preindustrial Climate 281
Evidence of cultivation in the Fertile Crescent is The first advanced civilizations of the early Egyptian
derived from preserved remains of grains found in dynasties developed between 6000 and 5000 years ago,
regions where the grains did not naturally grow and when the monsoon was still considerably stronger than
where their presence must have been aided by human it is today. Then and now, Egyptian life centered on the
efforts. Evidence of permanent occupation of villages river Nile, fed by monsoon rains in the Ethiopian high-
comes from the dental remains of animals from the lands and flowing northward through hyperarid desert
settlements. Layering in the teeth of these animals indi- (Chapter 8). When the Nile ran strong, large floods pro-
cates the season when they died. Because the animals vided fertile soils and moisture for farming along the
were killed in all seasons, the people must have stayed floodplain.
in the same place throughout the year. By 10,000 Climate in sub-Saharan North Africa turned much
years ago, people had begun to domesticate cattle and drier after 5000 years ago as the summer monsoon
other livestock in the Near East. Near the same time, weakened. This drying trend affected the civilizations
people also began to grow barley and other crops in that had come into existence and grown in size dur-
northern China. ing the wetter monsoon climates in the preceding
Because of the close association in time between the millennia. The weakening of the summer monsoon
later stages of the deglaciation and the origin of agricul- after 5000 years ago greatly reduced the extent of
ture, several cause-and-effect links have been proposed. summer flooding of the Nile. This change put greater
One seemingly plausible link is the possibility that the stress on populations that had expanded in response
change from the harsh (colder and drier) glacial climate to the stable food supply from large crop yields in a
to the more accommodating (warmer and wetter) cli- monsoonal climate.
mate provided conditions more favorable for humans to The Akkadian empire, centered in what is now Syria,
begin the grand experiment of growing crops. was the dominant civilization in Mesopotamia until
On the other hand, climatic data have been used as 4200 years ago. Evidence from archeological investiga-
the basis for a totally different hypothesis that centers on
the Younger Dryas climatic reversal between 13,000 and
11,700 years ago (Chapter 13). According to this idea, Yucatán
18
the Younger Dryas episode intensified the already dry lake δ O ( )
conditions across the eastern Mediterranean region and 1 2 3 4
forced people to retreat to dependable water sources. 0
In these more closely clustered conditions, people who
harvested and ate wild grains may have accidentally
scattered some grains near their threshing sites, with the Cultures
discarded grains sprouting in succeeding years as a form
of primitive farming. Some evidence places the time of 500
the earliest domestication of crops during the Younger
Dryas. Years ago Mayan collapse Mayan collapse Mayan collapse Postclassic
Neither of these directly opposed hypotheses is easy
to test. One problem is that agriculture may have begun Classic
earlier than the record indicates because the record is 1000
still incomplete (see Figure 15–7). Another problem is
that the beginnings of agriculture in each region on Late
Late Preclassic
Earth were one-of-a-kind events. Many such events, each
related to a similar change in climate, would be required
for a cause-and-effect relationship to be really conclusive. 1500 Early
15-5 Impacts of Climate on Early Civilizations
Climate change has been hypothesized as the cause of or
at least a major factor contributing to the deterioration FIGURE 15-11 Did drought destroy Mayan civilization? Lake
or collapse of early civilizations. One hypothesis focuses sediments indicate periods of prolonged drought during the time
on the role of an early flood (Box 15–1), but drought is a that Mayan civilization disappeared. (Adapted from J. H. Curtis,
more commonly invoked factor. In low-latitude regions D. A. Hodell, and M. Brenner, “Climatic Variability on the Yucatán
where water was scarce, civilizations were more suscep- Peninsula (Mexico) During the Past 3500 Years, and Implications for
tible to drought than to changes in temperature. Maya Cultural Evolution,” Quaternary Research 46 [1996]: 37–47).