Spotlight on Research: Surviving environmental change in the Middle Stone Age

An interdisciplinary "dream team" of Quaternary geomorphologists, archaeologists and geochemists are chipping away at the last 250,000 years of environmental change in central southern Africa, to help us understand how early humans dealt with difficult environments.

"Many people think deserts have always been deserts" says Professor David Thomas: however they have gone through hugely dynamic changes. "The emerging picture from our research is that today's Kalahari Desert once held one of the biggest lakes in the world, the size of Portugal and tens of metres deep."

Through state-of-the-art luminescence dating and isotope analyses, desert sediments can unlock the secrets of thousands of years of environmental change, generating detailed climate, vegetation and hydrological histories. However, as well as digging deep into the Kalahari's landscape, this latest research project looks at the human artefacts found on the surface too.

Previous work by Dr Sallie Burrough and Professor David Thomas revealed an abundance of archaeological treasures - thousands of waste flakes and fragments of hunting tools used by our Stone Age ancestors - spread over hundreds of kilometres of dry lake floor. Until now, no one has explored the relevance of these relics: how the tools got there, why they are on the ancient lake floor, and how humans fit in to this puzzle of environmental change in the region?

In the field for several weeks each year, an Oxford-led interdisciplinary team explores these questions. They take 'cores' of the ancient lake mud, and map and sample landforms and sediments. Archaeologists Dr Sigrid Staurset (SoGE), Dr Sheila Coulson (Oslo), Dr Sarah Mothulatshipi and students from Botswana painstakingly log and collect the artefact scatters. These fragments of 'silcrete lithics' help build a picture of how early humans used and moved around individual sites.

"Silcrete is perfect for tool-making," Thomas explains. "It breaks with a glassy sharp-edge, and it is a natural resource of deserts. What is more, each source-area patch of desert silcrete has its own unique geochemistry, inherited from the local water and parent sediments."

As part of the project, Professor David Nash (Brighton) has been expanding a Kalahari "silcrete geochemistry database". This means the team can now effectively "finger print" the basin's stone tools, to see where materials were sourced, adding to the picture of early human mobility in Africa. "Our findings suggest a complex ancestral use of the region, dispelling the idea that early humans only used deserts when they were really wet in the past," explains Thomas.

The region's "hidden history" can help unravel complex relations between people, environment and mobility - factors that underpinned Homo sapiens' ability to eventually colonise the whole globe. "This desert holds the promise of key answers to big questions surrounding human origins. It is now important that we put this neglected part of Africa on the map by making it a world heritage site," says Professor David Thomas.

"The central African desert region has some fascinating stories to tell."

David Thomas, Professor of Geography
School of Geography and the Environment, University of Oxford.

• The Leverhulme Trust

Prof Dave Thomas, Dr Sallie Burrough in collaboration with researchers at the University of Botswana, the University of Brighton and the University of Oslo. The Leverhulme Trust; 2016-2019.