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| By Kenneth Chang ABCNEWS.com If it weren’t for a prolonged cool spell about 12,500 years ago, perhaps we’d still be hanging out as hunter-gatherers and never bothered with civilization. At that time, a major source of food for people living in the Middle East was vast fields of einkorn, wheat, barley and rye. These plants, particularly sensitive to cool temperatures, suffered when the warmth since the last Ice Age was interrupted by a 1,000-year-long cool and dry period called the Younger Dryas. Necessity is the Mother of Farming The beginnings of farming appear to coincide with the Younger Dryas.
According to Ofer Bar-Yosef, an anthropologist at Harvard University’s Peabody Museum, that’s no coincidence. Instead of relying on what was growing naturally, he says, people started clearing land and planting seeds to insure they would have enough food. “It caused people to initiate cultivation,” he says. Bar-Yosef’s findings also narrow the location of the first farmers to the western half of the “Fertile Crescent” — an arcing swath of the Middle East, from the Persian Gulf north to Turkey and then back down through Syria, Lebanon and Israel toward Egypt. According to Bar-Yosef, the wild varieties of grains thrived in the western region and were transplanted elsewhere later. As people settled down and developed agriculture, towns and eventually civilization arose. That’s not the only time that climate may have shaped the course of humanity. Bar-Yosef and other researchers presented findings about climate and civilization last Saturday at the American Assocation for the Advancement of Science meeting in Anaheim, Calif. “We are probably more affected more by weather and climate than we think we are,” says Paul Mayewski, director of the Climate Change Research Center at the University of New Hampshire and another of the speakers at the Anaheim session. Not Always Like Today Until a few years ago, most scientists believed the climate of the past 11,000 years — a period known as the Holocene that followed the Younger Dryas — has been stable and uninteresting, and thus of little influence on the fortunes of civilization. However, climate records reconstructed from ice and sediment cores around the world paint a less benign weather history. While the temperature and rainfall swings haven’t been as wild as some periods in Earth’s history, they do appear enough to topple nations.
In 2280 B.C., a civilization called the Akkadians absorbed Tell Leilan. A century later, the town had emptied out and remained unpopulated for three centuries. The entire Akkadian civilization collapsed and disappeared. “There is a depopulation, desertion of northern Mesopotamian region,” says Harvey Weiss, professor of prehistorical archaeology at Yale University, who led excavations at Tell Leilan, “and Tell Leilan’s abandonment is simply typical of that process.” Long Drought Climate records show rainfall dried up in the Middle East around 2200 B.C., which would have deprived farmers of needed winter rains. In cores dug up in the Gulf of Oman to the south, sediments deposited during this time show very different minerals, indicating different wind patterns. Other archaeological sites show that cities to the south, surrounded by irrigated fields, swelled in population at the same time. When the climate connection to the Akkadian collapse was first presented a few years ago, some wondered whether farmers had inadvertantly caused their own ruin by overfarming. Data from other researchers gleaned from lake sediments around the world indicate the 2200 B.C. climate shift was a global event. “This has now put a lot more details together for it,” Weiss says.
Another major climate swing was the Little Ice Age, which froze Europe in the 1400s and killed off Viking settlements in Greenland. And perhaps also the one occurring today. Temperatures, nudged up by emissions of greenhouse gases, have risen sharply since the beginning of the century, but the wind patterns are largely unchanged, creating an unnatural combination of conditions. “You put those two together,” Mayewski says, “you have potentially greater instability in climate. It could turn out it is more important that humans have changed the stability of climate than just the temperature.” Those potential instabilities — droughts, heat waves, fiercer storms — could change the course of history yet to come. 
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S U M M A R Y A cool shift in climate may have spurred the start of farming and civilization.
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