News Release

East African artifacts support evolution of symbolic thinking in Middle Stone Age

Peer-Reviewed Publication

Arizona State University

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New finds from an open-air archaeological site in the Serengeti National Park in Tanzania have intriguing implications for the evolution of modern human behavior, including further indications that symbolic thinking developed in humans earlier than the currently accepted date of about 35,000 years ago.

Archaeologists studying the site say it may contain some of the strongest evidence yet for the early development of modern cultural behavior in humans, and is the first such discovery of its kind in East Africa, indicating that cultural modernity may have been widespread across Africa during the Middle Stone Age.

In a presentation to be delivered at the annual Paleoanthropology Society meeting on March 31 in Montreal, an international team of scientists will discuss recent findings at a site in the Loiyangalani River Valley in the Serengeti National Park. The researchers will report that preliminary excavation has yielded ochre pencils, bone artifacts, fish bones, mammal bones and two ostrich egg shell beads in association with an assembly of Middle Stone Age tools. There are other ostrich eggshell fragments that may represent debris from bead manufacture. The Middle Stone Age in East Africa originates as early as 280,000 years ago, and is replaced by the Later Stone Age at about 45,000 years ago, though none of the Loiyangalani finds have been precisely dated as of yet using advanced dating techniques.

Presenting the paper are J.C. Thompson from the Department of Anthropology at Arizona State University, project co-director J.R.F. Bower (Professor Emeritus, Department of Anthropology at Iowa State University and research associate in the Department of Anthropology at the University of California – Davis), E.C. Fisher from the Department of Anthropology at the University of Florida, project co-director A.Z.P. Mabulla of the Archaeology Unit at the University of Dar es Salaam, C.W. Marean from the Institute of Human Origins and Department of Anthropology at Arizona State University , K. Stewart from the Canadian Museum of Nature and C.F. Vondra from the Department of Geological and Atmospheric Sciences at Iowa State University.

"Some of the artifacts, in particular the ostrich egg shell beads are rare or unprecedented in the Middle Stone Age," said Marean. "Beads were not previously believed to be present in the Middle Stone Age and nothing like this has been published in Africa."

Until relatively recently, it was generally believed that human "behavioral modernity" -- the ability to think abstractly and to create culture and art – developed in humans significantly after Homo sapiens evolved to its present physical form (circa 120,000 years before present) and first in Eurasia, where human art and sophisticated artifacts begin appearing about 35,000 years ago. Recent evidence, including important discoveries of sophisticated bone tools from Blombos Cave in South Africa dated at more than 70,000 years old, have weakened this argument, showing that human tool technologies were significantly advanced before humans left Africa. The decorations on two ochre pieces from Blombos Cave have been interpreted as signs of symbolic activity, but that interpretation is debated.

The researchers see the beads as significant indicators of human cultural modernity because beads are clearly decorative, and decoration strongly implies abstract and symbolic thinking. "These beads are particularly significant because the symbolic nature of the Blombos bone tools and decorated ochre has been debated. The beads are unambiguous examples of symbolic behavior," Marean said.

Ostrich egg shell beads may also be indicators of even broader cultural developments. While there is no evidence of how the beads were used, ethnographic studies of recent African hunter-gatherer societies show that modern beads of this type are often used in trade between groups.

The methods that are used to produce ostrich shell beads are also significantly more sophisticated than any techniques used to produce the tools generally found in the Middle Stone Age. The beads, which are still produced by African Khoi-San (Bushman) cultures today, are typically produced by breaking the shell into small pieces, which are then drilled and strung on a fiber or sinew. The strung shell fragments' edges are then smoothed and rounded as a group to produce uniform beads.

The site was discovered by project co-director Bower and first test excavated in 1979. Since then the site has been excavated by Bower and Mabulla in 2000 and 2003 as a joint effort in the project known as Serengeti Genesis (, a project focused on the record for the origin of modern humans in the Serengeti ecosystem. The excavation site is in the broad floodplain of the Loiyangalani River and has yielded both Middle and Later Stone Age artifacts. Though the area shows signs of habitation through a wide range of human history, Bower and Mabulla do not think it is likely that the beads or any of the associated items could be Later Stone Age artifacts that were mixed with the Middle Stone Age tools by past soil disturbance at the site. This conclusion results from the fact that the stone tools are all Middle Stone Age and the sedimentological analysis of the site by Vondra indicates that is it unlikely that LSA beads could have contaminated the MSA deposits.

"I'm fairly sure that these items are very old, and if that is so this could be a very important site," Marean said. "The beads are a tantalizing find and once we get some definitive dating it could have a major impact on the issue of the evolution of symbolic thinking. We hope that further digging at the site will yield more information. Ultimately it is going to take wider excavation to resolve the questions."


This research was sponsored in part by grants from the Leakey Foundation and the National Geographic Society.

Sources: Curtis Marean, 480-965-7796, (after 3/29, 514-982-6064)
John Bower, 530-297-5648,
Audax Mabulla, 255-51-277-2339,
Mobile phone in Tanzania 255-0748-382300


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