Beer, scientists have long argued, helped give rise to civilization in an arc of land that sweeps from modern-day Egypt to the border between Iraq and Iran. Today, chemical analysis of barley grains, one of beer's key ingredients, is bolstering research into climate change’s role in the collapse of ancient societies.

"There has been a longtime debate about the relationship between climate and its changes and the development and in some cases demise of cultures," Frank Hole, an emeritus professor of anthropology at Yale University in New Haven, Conn., and a study co-author, explained to NBC News. "The research that we did is attempting to pinpoint this more directly."

To do this, he and colleagues collected samples of modern and ancient barley grains throughout the Near East and analyzed them to tease out the impact on agriculture of so-called mega-droughts over the past 10,000 years. The existence of these droughts has been inferred from sources such as pollen and microscopic animals in cores of soil pulled from lake and ocean bottoms.
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Archaeological researchers are using stable carbon isotope data from archaeobotanical barley grains to measure drought stress signals to study climate-related changes in agricultural production.

"What's new in this paper is that barley grains excavated at archaeological sites across the Near East also reveal the same abrupt climate changes," Harvey Weiss, who studies Near Eastern archaeology and the environment at Yale University, told NBC News. He was not part of the new research, which he added "shows that even with human cultivation practices, these drought periods are well marked."

The evidence stems from the way carbon isotopes in barley vary with water availability. "Together with other archaeological information they can provide a clearer picture on the fate of ancient societies," study leader Simone Riehl, an archaeologist based at the University of Tübingen in Germany, told NBC News in an email.

Diverse Impacts

The barley analysis indicates that drought stress was indeed an issue for these ancient societies, "but its regional impact was diverse and influenced by geographic factors," Riehl, Hole, and colleagues write in a paper published today in the journal Proceedings of the National Academy of Sciences.

For example, coastal farmers were largely unaffected by the droughts and grew copious amounts of barley for beer, bread, and other staples. Further inland, societies were forced to adapt when rains failed to materialize. Some developed irrigation systems. Others switched to more drought tolerant crops. "Sometimes they adapted by getting out and moving someplace else," Hole said.

Abandonment, he added, still happens in modern times. In Syria, for example, about 70 percent of the country's agricultural villages were abandoned during a drought that lasted from 2006 to 2010.

"People moved westward, where the water is in effect, but also where the big cities are. They wound up in places like Aleppo and so you have Aleppo being filled with refugees from these farming areas just at the eve of the Arab uprising and these (refugees) then became fodder for the uprising," he said. Drought also underpinned the flight of migrants from Oklahoma during the dust bowl of the 1930s, he added.
Lessons for the Future

The ancient droughts in the Near East occurred in the absence of human influence such as burning fossil fuels that fill the atmosphere with greenhouse gases, arrived abruptly, and surprised local populations, according to Weiss. "They differ in that regard from our present world where we know precisely what is happening, we know when it is happening, and we know what its effects are and will be," he said.

"In that regard," he continued, "these ancient mega-drought occurrences are a very strong and reinforcing lesson for us who have the ability to literally understand the present and see the future … to take positive action to either avert what we see coming or mitigate its effects and protect our populations."
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