Primate tools and the search for human behaviour

This is the second in a short series of articles to accompany the Stone Age Primates temporary display at the Museum, created with the Primate Archaeology group at Oxford University. Here, Dr Tomos Proffitt, Postdoctoral Research Assistant in Primate Archaeology, shows how the use of stone tools by modern primates might connect with our earliest human ancestors.

Over the past five years I have been fortunate enough to work with and study some of the earliest known stone tools, uncovered from archaeological sites at Olduvai Gorge, one of the most famous Palaeolithic archaeological sites on our planet. Olduvai Gorge seemingly appears out of nowhere as you drive down the dirt tracks of the north western slope of the Ngorogoro caldera and national park in Northern Tanzania.

The view from the top of Naibor Soit overlooking Olduvai Gorge. Photo Credit: Tomos Proffitt

The view from the top of Naibor Soit overlooking Olduvai Gorge. Photo Credit: Tomos Proffitt

It is here that the famous Louis and Mary Leakey uncovered evidence which proved that our evolutionary origins extended not thousands, but millions of years into the past, and over the years the site has provided a wealth of animal and early human, or hominin, fossils as well as tens of thousands of examples of the stone tools they made.

Two million years ago if you were sitting where I was in Olduvai, the most noticeable feature would have been a great lake surrounded by vast floodplains, occupied by a range of herbivorous and carnivorous animals taking advantage of the abundant grass, shrubs and fresh water constantly feeding the lake. It is in this setting that you would have found small groups of our hominin ancestors (Homo habilis) standing upright and walking across the floodplains in search of food.

Lake Ndutu located at the south western end of Olduvai Gorge. Early hominins would have occupied a similar lake environment. Photo Credit: Tomos Proffitt.

Lake Ndutu located at the south western end of Olduvai Gorge. Early hominins would have occupied a similar lake environment. Photo Credit: Tomos Proffitt.

As a large part of my research involved closely studying and analysing the stone tools used by the hominins who once lived in this landscape my thoughts turned to how these individuals would have used tools for the different tasks they faced.

Once this hominin group had found a partially eaten carcass, possibly that of a Deinotherium (an extinct ancestor of the modern day elephant), they would have set about trying to make the most of this valuable resource.

By using quartz flakes with extremely sharp cutting edges, made by striking a quartz block with a round hammerstone cobble, they would have been able to cut the small scraps of meat that were still attached to areas of the carcass untouched by other predators, such as lions, hyenas, wild dogs and vultures. The hominins, would, however, also have been very interested in the leg bones because they contained an incredibly nutritious food source than not many other animals could easily get to – the bone marrow.

Examples of quartz anvils used by early hominins at Olduvai Gorge. Photo Credited to Mora and de la Torre, 2005.

Examples of quartz anvils used by early hominins at Olduvai Gorge. Photo Credited to Mora and de la Torre, 2005.

After butchering the animal they would have carried the meat and bones back to another group, some of whom had been collecting various nuts and roots and were now busy preparing them to be eaten. They would be cracking open the nuts and pulverising the roots on a large flat quartzite anvil using rounded hammerstones. The group that had just arrived would have used the same tools to carefully open the elephant leg bones to access the marrow inside. A whole range of dynamic food gathering, eating, sharing, learning, teaching, tool making, communicating behaviour was taking place at this location.

Fast forward 2 million years: since that original meal, the site has been repeatedly buried in sand and sediment and eroded by flowing water and the only thing that remains from this location of vibrant activity and of the lives of these hominins are a few fossilised bones and a small collection of fragmented and broken stones. This is the type of material we were excavating in 2015.

Archaeologists use a range of methods to try and understand how stone tools were used and some of the most powerful insights can be gained through observing how stone tools are used today.

Chimpanzees using both a hammerstone and anvil to crack open nuts. Photo Credit: Haslam et al, 2009

Chimpanzees using both a hammerstone and anvil to crack open nuts. Photo Credit: Haslam et al, 2009.

Transport yourself now to a small forest clearing in western Africa, where a group of our closest living relatives, chimpanzees, are quietly sitting underneath a number of nut- and fruit-bearing trees. This group is taking advantage of these important food sources, and is doing so by using stone anvils and stone hammers not too dissimilar from the group of hominins at Olduvai Gorge, two million years earlier.

A hammerstone used by a capuchin, on display in the Museum

A hammerstone used by a capuchin, on display in the Museum

But it is possible to directly observe the chimpanzee behaviour, recording how the tools are being made and used, what waste is being produced, the learning processes going on between infant and adult, and the range of social interactions that are happening. This modern primate behaviour represents a valuable window into the types of activities that some of our earliest hominin ancestors may have also undertaken.

The Stone Age Primates exhibit at the Museum showcases these types of stone tools and how they are used by modern primates. By closely studying how our closest living primate ancestors, including chimpanzees, capuchins and macaques, make, use and discard stone tools it is becoming increasingly possible to better understand the dynamic range of early human behaviours behind similar types of hammers and anvils found at Olduvai Gorge and other East African archaeological sites.

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