Recasting plaster in Late Stone Age.

Recasting plaster in Late Stone Age

The Neolithic or Late Stone Age was a time of tremendous social and technological change in the Near East. Until recently, many saw it as a revolutionary period leading to the formation of the first complex societies. For instance, researchers have maintained that the domestication of crops and animals swept the Near East around 8,000 B.C., causing nomadic hunters and gatherers to settle down in villages and intensify agricultural production. Another swift change occurred about 6,000 B.C., with the appearance of high-quality ceramic pottery.

But the Neolithic "revolution" is being reassessed. Recent work at several Near East sites reveals a step-by-step introduction of domesticated plants and animals, beginning around 9,500 B.C., sometimes in the absence of farming villages. And according to a study in the just-released summer JOURNAL OF FIELD ARCHAEOLOGY, the technology required for pottery making formed the basis of an extensive plaster industry long before ceramics gained popularity. Plaster production rapidly expanded between 7,200 B.C. and 6,000 B.C., the investigators report.

"Describing the Neolithic in terms of the invention of pottery, plaster and agriculture is incorrect," says study director W. David Kingery of the University of Arizona in Tucson. "It was rather a period of industry establishment based on much earlier inventions."

Kingery and his colleagues examined 36 samples--typically 1 cubic centimeter or smaller -- taken from Neolithic artifacts thought to be made of plaster. The artifacts, including flooring material, containers, sculptures and ornamental beads, are now housed in museums around the world and represent sites throughout most of the Near East.

Although some artifacts were unearthed decades ago, this is the first analysis of their microscopic and chemical makeup. Researchers studied fractured surfaces with a scanning electron microscope, including a procedure to identify the chemical composition of each specimen.

The investigators uncovered the microstructure of two types of plaster: lime and gypsum. Lime artifacts came primarily from sites in what is now Israel and Turkey; gypsum specimens originated in Syria and sites further east. Production of these plasters in quantity requires a number of steps, Kingery notes. Large amounts of wood must be gathered to heat limestone at 800 to 900[deg.]C (gypsum at 150 to 200[deg.]C) for up to several days. This product is then soaked in water to form a paste. Various substances, such as sand or gravel, are then added, and the paste is applied and shaped for a particular use. Many artifacts examined in the study show evidence of a thin plaster overcoat containing dye, as well as burnishing. This suggests plaster manufacture was a skilled activity conducted by special craftsmen, Kingery says.

In his view, the growth of villages and farming created a need for durable storage vessels demanding less fuel in their production, thus leading to the replacement of plaster containers by ceramics.

The earliest plaster artifacts in the sample -- several stone blades with lime plaster used as an adhesive material -- date to about 12,000 B.C., near the beginning of the Neolithic. The first evidence of plaster as an architectural material occurs between 10,300 and 8,500 B.C.

"The technological advances in plaster making [uncovered by Kingery and his co-workers] are unanticipated," says Yale University archaeologist Frank Hole, who granted the researchers access to several plaster artifacts. The first written records of job specialization in the Near East occur around 2,500 B.C., shortly after the Neolithic period ended. But there is no solid evidence for social complexity or craft specialization accompanying earlier plaster manufacture, Hole adds.

Kingery disagrees. "As we delve more deeply into the technology of early [Neolithic] times," he says, "specialized societies appear earlier and earlier."