Looking for a recipe for a great civilization? How about: Take people, add water, and shake very, very vigorously. Earthquake-prone areas along the edges of tectonic plates were far more likely to give birth to great ancient civilizations than less dynamic landscapes, according to a new study. Researchers say the relationship suggests that forces typically viewed as destructive--such as earthquakes--might have also played a constructive role in human history.
"It's not a connection that seems to make much sense at first glance," says geologist Eric Force, the study's author. "But you can't ignore the pattern--look at a map, and it just jumps out at you."
Force first recognized the relationship while he was on a camping trip, trying to get to sleep. The geologist had recently retired after a long career with the U.S. Geological Survey and had been taking some university classes on ancient history. "I realized that a lot of the civilizations we were talking about sat right along major tectonic plate boundaries," says Force, who is now affiliated with the University of Arizona, Tucson. It wasn't long before he pulled out his geological maps and began trying to quantify the relationship, to see if the link was just a fluke.
It isn't, at least in Asia and Europe, Force reports in the current issue of Geoarchaeology. First, he mapped plate boundaries and what archeologists say are the birthplaces of 13 major ancient civilizations. They ranged from Rome and Corinth in Western Europe, to Memphis and Jerusalem in the Middle East, to historic sites in India and China. Then, Force calculated the probability that the sites were randomly located, given that plenty of suitable land was available for settlement. The number crunching suggests that 13 of the 15 sites aren't the product of chance. Instead, ancient people appear to have chosen to snuggle up close to a tectonic crack-- often within 75 kilometers--despite the risk of quakes, tsunamis, and volcanic eruptions. (The exceptions were in ancient Egypt and China.) The analysis did find that civilizations farther from plate boundaries seemed to persist longer, perhaps because they had to contend with fewer natural disasters.
Theories abound about why tectonic zones might have boosted the growth of early civilizations, says Force. Geologists know that plate boundaries often have ample water supplies that might have attracted early settlers, for example. And volcanoes can help create rich soils. But no factor explains the pattern, Force says. He is intrigued by a psychological explanation: "Maybe the elders are telling the kids that they'd better be prepared to cope with a lot of risk and change," he says--spurring the next generation to develop more sophisticated quake-resistant architecture, for instance, or create better ways to store food.
That idea appeals to archeologist Geoff Bailey of the University of York in the United Kingdom. "It could be that a certain level of geological instability demands organizational responses from the societies that live in such areas," he says, calling it "a sort of challenge-and-response theory of social development." In his own work, he's even speculated that similar tectonic challenges, and not just factors such as climate change, could have spurred the evolution of humans in Africa. A little shaking up, he suggests, isn't necessarily a recipe for disaster.