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Leicester Archaeologist Involved in Proving First Prehistoric Evidence of Chimpanzee Technology

Analysis of starch granules by Leicester researcher

University of Leicester archaeologist Dr Huw Barton has helped to confirm the first prehistoric evidence of chimpanzee technology- by analysing starch granules.

Dr Barton, Wellcome Trust University Fellow in Bioarchaeology, worked with a team of international researchers to uncover the truth from 4,300 years ago.

The study was led by a University of Calgary archaeologist who found the first prehistoric evidence of chimpanzee technology, adding credence to the theory that some of humanity's behavioural hallmarks were actually inherited by both humans and great apes from a common ancestor.

Dr. Julio Mercader, one of the few archaeologists in the world who studies the material culture of great apes, especially chimpanzees, uncovered stone 'hammers' last year in the Taï rainforest of Africa's Côte D'Ivoire (Ivory Coast) that date back 4,300 years.

Mercader and co-investigators from Germany, UK, the U.S. and Canada reported on the findings in the latest edition of PNAS, the Proceedings of the National Academy of Sciences. PNAS is in the top echelon of academic journals internationally.

"It's not clear whether we hominins invented this kind of stone technology, or whether both humans and the great apes inherited it from a common forebear," says Mercader, also a Canada Research Chair in Tropical Archaeology. "There weren't any farmers living in this region 4,300 years ago, so it is unlikely that chimpanzees picked it up by imitating villagers, like some scientists used to claim."

The stone hammers that the team discovered, essentially irregularly shaped rocks about the size of cantaloupes - with distinctive patterns of wear - were used to crack the shells of nuts. The research demonstrates conclusively that the artefacts couldn't have been the result of natural erosion or used by humans. The stones are too large for humans to use easily and they also have the starch residue from several nuts known to be staples in the chimpanzee diet, but not the human diet.

Using so-called "percussive technology" to free the edible parts of nuts is more complicated than it sounds. "We know that modern chimpanzee behaviour regarding nut-cracking is socially transmitted and takes up to seven years to learn," Mercader says. "Some of the nuts require a compression force of more than a thousand kilograms to crack. And the idea is to crack the shell but not smash it - it's not a simple technique."

The discovery suggests that a 'chimpanzee stone age' reaches well back to ancient times. "Chimpanzee material culture has a long prehistory whose deep roots are only beginning to be uncovered," the authors write.

Although it's difficult to prove whether the technology was adopted through imitation, another possibility is convergence - that is, both humans and great apes arrived at the technique independently.

"We used to think that culture and, above anything else, technology was the exclusive domain of humans, but this is not the case," Mercader says. Previous research that Mercader published in the journal Science in May 2002 has paved the way for the new sub-discipline of chimpanzee archaeology, which combines archaeology, paleo-anthropology and primatology.

LEICESTER’S INVOLVEMENT

Dr Barton’s role in the project was in the identification of starch granules from the surface of pounding tools used by Chimpanzees.

He said: “Julio has been working in the region for a few years, alongside Christophe Boesch, investigating stone tools used by a group of chimpanzees to crack nuts. Both humans and chimps like and use nuts, so in order to be sure we were looking at tools used by chimpanzees and not people (though the size and morphology of some of these tools strongly suggested that they were chimp and not human technology) we needed to find the direct evidence of the nut species utilised.

“Chimps eat some nut species that people do not, so if we could find direct evidence of the type of nuts used we would be on much firmer ground claiming that we are looking at an archaeology of chimpanzees and not an archaeology of human beings.

“This is where the analysis of starch granules becomes important. This is a developing technique in archaeology where we recover individual starch granules from the surface of stone tools and from archeological sediments. Surprisingly, we have found that starch can survive over quite long periods of time.

“I have recently been looking at starch on stone tools that are up to 40,000 years old from Niah Cave in Borneo. Starch is a three-dimensional granule that, like pollen and of similar size, varies in its size and shape between plant species. We can identify some plants to genus and species, if we are lucky.

“In this project we were able to recover starch from the surfaces of these stone tools of nut species that are exclusively used by chimpanzees. Some of these tools are up to 4,300 years old!

“I find the results of this fascinating for a number of reasons. The relative antiquity of this behaviour amongst chimps suggests independent innovation of stone tool use and raises the question of just how old this behaviour might be? Hominins have been using stone tools for over two million years; how long have our nearest relatives, the chimpanzees, been using simple stone technology?

“I also think that it is amazing that my lectures on the history of stone tool use, and my working definition of archaeology (the study of the material culture of people) will have to be expanded to include chimps too!”

Other researchers are excited about the work. "Mercader's paper presents strong archaeological data for the antiquity of nut cracking by chimpanzees and shows that this behaviour developed long before farmers arrived in the area," says Dr. Michael Chazan, a University of Toronto anthropology professor who specializes in Paleolithic archaeology.

"Of course, this article, like most great discoveries, opens as many questions as it answers. Why and how did this group of chimpanzees maintain nut-cracking behaviour while other chimpanzee groups living in locations with the same nuts available did not? It might be that the archaeology of chimpanzees will produce more surprises in the future."

Adds Dr. Alison Brooks, a research associate at the Smithsonian Institution and professor of anthropology at George Washington University: "The first non-human archaeological site of considerable antiquity raises interesting ideas about our common heritage with chimpanzees, as well as about the interpretation of early human sites, especially those in rainforests. The study of starches on the tools is particularly compelling evidence for association with chimps rather than humans. The authors should be congratulated for their research."

The new paper is titled, "4,300-year-old chimpanzee sites and the origins of percussive stone technology." Although reporters may interview Mercader beginning on Feb. 8, the story is embargoed until Feb. 12, 3 pm MST, under conditions set by editors at PNAS.

The other authors include Jason Gillespie (University of Alberta), Jack Harris (Rutgers University), Steven Kuhn (University of Arizona), Robert Tyler (University of Saskatchewan) and Christophe Boesch (Max Planck Institute for Evolutionary Anthropology).

The research was funded primarily by the Max Planck Institute for Evolutionary Anthropology, the Canada Research Chairs program and the University of Calgary. Institutional support came from the Smithsonian Institution and George Washington University.

Print-quality photos may be downloaded from the University of Calgary

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