"No one knows who these people were and where they came from, but by stone-age standards they surely had mastered at least one type of advanced technology," says Dr. Nissenbaum.
Nissenbaum added that the production of collagen glue placed the stone-age cavemen several thousand years ahead of the ancient Egyptians, a surprising technological feat for a group that had not yet mastered pottery.
Nissenbaum studied findings from the Nahal Hemar cave, which was probably used for cult purposes by ancient humans. This cave, located on a cliff near the Dead Sea just northwest of Mt. Sedom, has provided some of the most important regional findings from the late stone age known as the Neolithic period. One of the striking features of the excavated objects is the use of a black substance originally believed to be asphalt. It was applied as a protective lining on rope baskets, containers and embroidered fabrics, as a crisscross-patterned decoration on tops of sculptured skulls and as an adhesive holding together tools and utensils.
When Nissenbaum, who studied asphalt from different archaeological digs, conducted a chemical analysis of the blackish material, he was amazed to discover it was not asphalt at all but rather collagen, the most common fibrous protein in living organisms and a major component of skin, sinews and cartilage. Its chemical composition, as well as an electron microscope analysis of its structure, suggested it was derived from animal skin
Carbon-14 dating established that the collagen was about 8,100 years old, which coincided with the period when the cave was first used. Although collagen normally quickly converts into gelatin, the Nahal Hemar specimens were exceptionally well preserved due to the region's extremely dry climate.
Natural glues from animal and plant sources were extensively used from antiquity up to the early 20th century. With the Middle East's scarcity of trees, a common source of resin adhesives in ancient Europe, it is hardly surprising that cavemen turned to collagen as a glue. What is surprising, though, is that these people were far ahead of ancient Egyptians who used collagen in its gelatinous form as the basis for the "carpenter's glue" that held together furniture.
While the Egyptians apparently produced their "carpenter's glue" through heating and alkaline solution treatment of animal skins, it's unclear how the Dead Sea cavemen manufactured theirs. It is clear, though, that the stone age craftsmen supplemented the glue with plant-tissue additives, evidently in order to endow it with the appropriate texture.
These findings, reported in the Hebrew-language Archeologia Umada'ei Hateva ("Archaeology and Natural Sciences"), add a new chapter to the history of adhesives and to humankind's technological history in general. (An English translation of the paper is available, as are color slides of the ancient decorated skulls).
ADDITIONAL INFORMATION Dr. Nissenbaum serves as the Institute's Academic Secretary and conducts research in geochemistry and scientific archaeology. Excavations of the Nahal Hemar Cave were carried out by Prof. Ofer Bar Yosef of the Peabody Museum, Harvard University and David Alon of the Israel Antiquities Authority.