What happened about 3,200 years ago to bring about the collapse of not just one but a number of flourishing civilizations on the eastern shores of the Mediterranean?

A study of fossilized pollen particles taken from sediments at the bottom of the Sea of Galilee may have solved an intriguing historical mystery that has been troubling archaeologists for decades.

"In a short period of time, the entire world of the Bronze Age crumbled," says Israel Finkelstein, an archaeologist at the Institute of Archaeology at Tel Aviv University, who was one of the lead scientists in the study.

"The Hittite Empire, Egypt of the pharaohs, the Mycenaean culture in Greece, the copper-producing kingdom located on the island of Cyprus, the great trade emporium of Ugarit on the Syrian coast, and the Canaanite city—states under Egyptian hegemony—all disappeared and only after a while were replaced by the territorial kingdoms of the Iron Age, including Israel and Judah."

Wars, pestilence, and sudden natural disasters have all been postulated as possible causes, but now, thanks to sophisticated pollen-sampling techniques and advances in radiocarbon dating, Finkelstein and his colleagues believe they know the primary culprit: drought, or rather a succession of severe droughts over a 150-year period from 1250 BCE to about 1100 BCE.

These fairly precise dates come from core samples drilled into the sediments at the bottom of the Sea of Galilee. The drill cores extended 18 meters into the seabed and cut across a range of sediments deposited over the past 9,000 years.

Pollen: "Fingerprints" of Plants

"We focused our study on the time interval between 3200 BCE and 500 BCE," says Dafna Langgut, a University of Tel Aviv palynologist (one who studies ancient pollens). She, along with Finkelstein and University of Bonn geology professor Thomas Litt, authored the study, which appeared this week in Tel Aviv: Journal of the Institute of Archaeology of Tel Aviv University.

By studying pollen samples taken at 40-year intervals, the scientists were able to monitor changes in the vegetation. "Pollen grains are the 'fingerprints' of plants," says Langgut. "They are extremely helpful in the reconstruction of ancient natural vegetation and past climate conditions."

The scientists noticed a sharp decline around 1250 BCE in oaks, pines, and carob trees—the traditional flora of the Mediterranean in the Late Bronze Age—and an increase in the types of plants usually found in semiarid desert regions. There was also a big drop in the number of olive trees, an indication that horticulture was on the wane. All are signs, say the researchers, that the region was in the grip of regular and sustained droughts.

Shortages and Unrest

The most crucial years of the collapse were probably between 1185 and 1130 BCE, says Finkelstein, but the entire process extended over a longer period of time.

"I think that climate change can be seen as a sort of a 'prime mover' that initiated other processes," says Finkelstein. "For example, groups of people in the northern regions were uprooted from their homes because of destruction of the agricultural output, and [they] started moving in search of food. They could have pushed other groups to move by land and sea. And this in turn caused destructions and disruption of the delicate trade system of the eastern Mediterranean."

The dates the researchers came up with via pollen analysis correspond nicely to the few remaining historical records of the period, which mention shortages of grain, disruption of trade routes, civil unrest, and pillaging of cities as people began to fight over diminishing resources. The Late Bronze Age was also a period when marauding bands known as the Sea Peoples raided coastal areas in the eastern Mediterranean.