Stone tools and evolution

Technology and tools

Today when we talk about ‘technology’, we tend to think of computers and machines – complex feats of engineering that we rely on in the digital age. But if we think about what technology is in its simplest form, it boils down to the skills, knowledge and tools that help us to accomplish a task. A tool, then, is any object we use to help us carry out a task.

Humans are not unique in using tools in this sense – sea otters use rocks to break open mussel shells, Capuchin monkeys use a hammer-and-anvil technique to crack nuts, and New Caledonian crows can even be said to make tools when they bend a stick to make a hook. Chimpanzees use tools with such regularity, complexity and in sets that vary between different groups that we even talk about chimpanzee ‘culture’.

Chimpanzees are our closest living ape relative with whom we share almost 99% of our genes. In evolutionary terms, the shared human and chimpanzee branch of our family tree split apart 6 to 8 million years ago. Like us, chimpanzees are innovators and teachers; they invent new tools and this knowledge is passed on to others through generations. We can even study the archaeology of chimpanzees and other primates.

What is it, then, that sets humans apart?

Who made the first tools?

Humans, and our ancestors, have been using tools for at least 3.3 million years. The oldest known stone tools come from the site of Lomekwi 3 in Kenya. We are not sure who actually made these earliest tools. Besides Lomekwi, our oldest tools are 2.6 million years old from two different sites, Gona and Bokol Dora, in Ethiopia.

Scientists had thought that the first tool-makers belonged to our own genus Homo, with an early Homo habilis (literally “Handy Man”) fossil dating to 2.8 million years ago, but new discoveries like Lomekwi mean we have to rethink this. The fossil hominins we know were around 3 million years ago belong to the genus Australopithecus or Kenyanthropus which challenges the idea that stone tool-making is a uniquely human trait.

The big puzzle of origins

Given how often we have to revise our thinking when we discover the new ‘oldest’ examples of fossils and tools, the very early stages of our past are quite messy. The sort of evidence we are dealing with is like a jigsaw puzzle with pieces missing. Usually when fossils are found, they are very fragile, incomplete and often need to be painstakingly put back together. Then the bigger picture of how all of these fossils fit together into a family tree is also full of missing pieces. The fossil record for the past 4 million years of our past is currently represented by only about 6000 individuals – a minute fraction of the total number of people who have lived on Earth. It is actually very difficult to become a fossil (find out how here). You have to die in the right place, be buried under the right conditions for long enough for your bones to fossilise, and eventually be discovered, so the odds are slim.

There are two ‘Cradles of Humankind’ in Africa where most of the known fossils come from due to these very specific conditions – buried in layers of volcanic ash in the East African Rift Valley, or limestone cave systems near Johannesburg in South Africa. These are obviously not the only places in Africa that ancient humans lived, as other tantalising fossil finds hint at.

Carpets of stone

While it is not a given that bone will fossilise into stone, there are plenty of artefacts made of stone waiting to be found by archaeologists. In the Sahara Desert, a seemingly inhospitable environment, scientists have described “carpets of stone tools” lying on the land surface. Researchers carrying out surveys in the Messak region of Libya, recorded an average of 75 stone artefacts every square metre, dating to the Early and Middle Stone Ages.

Rob Foley and Marta Mirazón Lahr have calculated that for the whole of Africa, there is an average density of between 0.5 and 5 million stone artefacts per square kilometre. In terms of volume of stone, this is the equivalent of 84 million Great Pyramids of Giza (2.5 x 10⁶ cubic metres). That would be the equivalent of finding 1.3 to 2.7 Great Pyramids per square kilometre across Africa.

Stone tools in the Tankwa Karoo

Arid environments like the Sahara offer archaeologists a number of advantages: low rainfall means there is very little vegetation to obscure the ground, and an eroding sandy, rocky land surface leaves stone tools lying exposed on what we call a desert pavement. Rather than having to dig down into the ground to find archaeological evidence, landscapes like these give us insights into how past people behaved at big spatial scales, not just the small windows that excavations provide.

The Tankwa Karoo is another arid region with ideal conditions for studying how humans lived in their landscapes. Just like Foley and Lahr’s study in the Sahara, in one area of 150 x 1000 m (150,000 m²), my survey team and I recorded an average of 36 stone tools per square metre – that gives an estimate of roughly 5.4 million stone tools just in that place.

Our research in the Tankwa Karoo has covered an area 100 km across, recording over 23,000 stone artefacts in our samples (all of which we left behind where we found them), which span at least the past million years.

As you might expect, people in the past did not use the whole landscape uniformly. In the way that we use spaces differently in our houses, they left more material traces at certain sites (rooms), but relatively few objects remain in the spaces in between (corridors). By walking across the landscape and recording the types and numbers of artefacts we find in different places, we can build up a picture of where people went, what they did, and how they interacted with their environment.

Hunting and gathering

For more than 90% of human history, our ancestors have been hunter-gatherers, meaning that they had to range over large areas to hunt and gather their food from their surroundings. The Tankwa Karoo has plenty of stone which people could easily find to make tools from, but tracking down animals or finding edible plants and water in a desert environment would have been more of a challenge.

Desert-dwelling animal and plant species have developed special adaptations that help them to live on very little food and water in these harsh conditions. Humans have an extra way of adapting – we can use technology to help us survive.