Researchers from Ohio State University are examining cores from glaciers atop peaks in the Peruvian Andes -- as well as preserved plants retrieved from the ice -- to help determine whether a sudden, worldwide drop in temperatures changed daily life for the inhabitants of South America, Europe and Asia.
"Something happened 5,200 years ago that was abrupt and very large-scale," explained Lonnie Thompson, OSU professor of geological sciences.
During a core-drilling expedition in 2002, Thompson's team found a wetland plant that had been remarkably well-preserved under the ice. DNA from the plant was tested and dated back 5,200 years.
"This is a soft-bodied plant," he said. "It had to be captured by a very large snowfall at the time, a snowfall and climate change that began very abruptly -- fast enough to capture a plant but not kill it. That is astounding."
The "Ice Man," a preserved Neolithic hunter exposed by a retreating glacier in the European Alps, also was trapped by the ice around 5,200 years ago, "and that had to occur very abruptly," Thompson said.
Earlier work by the Ohio State team on cores taken from Tanzania's Mount Kilimanjaro ice fields suggested a catastrophic drought had devastated Africa's tropical region more than 5,000 years ago, when many anthropologists think people abandoned nomadic lifestyles to form cities and social structures.
"If it happened in the past, it might happen again," Thompson warned, "and that type of abrupt event in today's world would mean worldwide chaos, both economically and socially."
About 70 percent of the world's 6.4 billion people live in the tropics.