New Look at Ancient Puzzles

Ancient sites are revealing new secrets, thanks to Weizmann Institute researchers, who are active in applying modern science to the traditionally humanities-based field of archaeology to create a new discipline, scientific archaeology.

"There's a need to provide a scientific basis for the unraveling of archaeological mysteries," says Prof. Steve Weiner, the geochemist who heads the Institute's Environmental Sciences and Energy Research Department.

Weiner's astute application of chemistry to archaeology recently led to an important discovery: how to recognize and analyze prehistoric ashes with precision. The finding throws light on the use of fire and the lifestyles of early humans, and on their environment. As a result of the discovery, Weiner became the first Western scientist in 60 years to work at China's Zhoukoudian cave, which houses the bones of Peking Man, believed to be among the first humans to use fire. Weiner and his colleagues will spend the next year analyzing samples they brought back from China and reexamining what were thought to be closed questions about the famous site.

While humans are believed to have first harnessed fire some 500,000 years ago, ash -- the most direct evidence of fire -- is hard to find and even harder to recognize, because most of its minerals are highly reactive and unstable and begin changing within days after a fire has gone out. Bringing chemistry to bear, Weiner discovered that a small relatively stable group of mineral survives these changes and can serve as a telltale sign of ash even after thousands of years.

Weiner made his discovery while studying sediments in prehistoric caves in northern Israel which had been inhabited as far back as 250,000 years. He found that the sediments -- in some places several meters thick -- were largely made up of ash minerals, a finding that shows the caves were intensively inhabited over millennia. Weiner and colleagues are now seeking to distinguish between periods of occupation and nonoccupation of the caves, on the assumption that ash would be present only in sediments from periods of occupation.

The prehistoric cave study involves a long-standing collaboration between Weiner, archaeologist Prof. Ofer Bar-Yosef of Harvard University, and geologist Prof. Paul Goldberg of Boston University. It is the first archaeological dig anywhere to incorporate an on-site laboratory, including a portable infrared spectrometer.

For nearly three decades, the Weizmann Institute has operated the Middle East's only radiocarbon dating laboratory. Now run jointly with the Israel Antiquities Authority, the laboratory has dated hundreds of artifacts, including the "Jesus Boat," a wooden fishing vessel found in the Sea of Galilee and shown to be 2,000 years old; preserved lentil seeds, proof that organized agriculture began in Israel at least 9,000 years ago; pieces of cloth from the Masada fortress that provide evidence the skeletons discovered there belonged to its Jewish defenders; and, most recently, wooden beams from an ancient structure just west of the Israeli-Egyptian border that served as a "bed and blessing" stopover and provided travelers with religious services "for the road".