Pollen grains are one of the most durable organic materials in nature, best preserved in lakes and deserts and lasting thousands of years. Each plant produces its own distinct pollen form, like a fingerprint. Extracting and analysing pollen grains allows researchers to identify the vegetation that grew in the area and to reconstruct climate changes. "Understanding climate is key to understanding history," says Professor Finkelstein, of the Institute of Archaeology at Tel Aviv University.
     Experts have long pondered the cause of the crisis that led to the fall of Middle East civilisations in the Late Bronze Age, and now believe it was drought that led to the collapse more than 3200 years ago. As a result of this climate change, "in a short period of time the entire world of the Bronze Age crumbled," explains Professor Finkelstein.
     High-resolution analysis of pollen grains taken from sediment beneath the Sea of Galilee and the western shore of the Dead Sea, coupled with radiocarbon dating, have pinpointed the period of crisis to the years 1250 to 1100 BCE. Recent studies of pollen grains conducted by experts in southeast Anatolia, Cyprus, along the northern coast of Syria and the Nile Delta came up with similar results, indicating that the crisis was regional.
     The results showed a sharp decrease in the Late Bronze Age of Mediterranean trees like oaks, pines and carobs, and in the local cultivation of olive trees, which the experts interpret as the consequence of repeated periods of drought.
     The study also draws on a case study of another regional collapse 2,000 years later to explain why, unlike in the steppe regions, a decrease in precipitation would have such a destructive effect on established city-states in green areas like Megiddo. The droughts were probably exacerbated by cold spells, causing famine and the movement of marauders from north to south.

Edited from The New York Times (22 October 2013), PhysOrg (24 October 2013)