Kenyan farmer’s unique rock find uncovers new prehistoric clues

A prehistoric hand-held multipurpose stone tool the size of a person’s palm recovered by a farmer in Kenya. More tools were found during a search. Stephen Thompson

Untold numbers of relics from our human past lie along cattle paths, on farms and in remote expanses across Africa. These include fossilised bones of ancients and the animals they preyed on as well as hearths, tools, jewellery and even footprints.

The most durable of these prehistoric calling cards often comprise stone tools. But it’s not easy determining what’s prehistoric and special, and what’s not. In rare cases someone will recognise a piece of stone that stands out, or appears modified and call attention to it. This is what happened earlier this year at Eor Enkitok village in Narok, Kenya. Francis Yaipan picked up a tear-drop shaped rock on his family farm that puzzled him so much that he made contact with the Kenyan National Museum.

The unique piece of rock, carefully crafted on both sides, turned out to be a hand-held multipurpose stone tool the size of a person’s palm. It was crafted by a human ancestor using locally available volcanic rock tens of thousands of years ago. An initial visit by Nairobi museum scientists established that there were more prehistoric tools in eroded volcanic ash layers nearby.

The world’s oldest tools date some 3.3 million years and are from Lomweki in Turkana in northeastern Kenya. Kenyan sites boast a record of human cultural evolution that charts stone tool technological progress from 3.3 million years to 800 years ago.

But the evidence from Kenya and other African prehistoric sites is not sufficient to paint a clear picture of the first appearance, duration and variation of technologies found so far. Just as important is knowing which of these technologies are definitively made by our species – Homo sapiens – and which were made by Homo erectus.

The Narok finds are significant because they straddle two technological phases. These are:

  • the Acheuluen, a technology that is traced to Homo erectus, and

  • the Middle Stone Age, technology firmly linked to our species.

Early humans occupied this locality

I was part of a bigger team that returned to the Narok site in August 2016. At the top layer, the scientists found small tools in shiny obsidian. In the middle and lower layers, few obsidian tools were found and those present had carbonate impurities in them that rendered them less useful for making tools.

The sequential layers consisted of prehistoric soils sandwiched between layers of volcanic ash. The ash from volcanic activity would have been deposited repeatedly over extended periods of time. It was rapidly sealed and protected surfaces from erosion, preserving them for posterity. The site was also used by other generations during periods of geological respite.

A 2.5cm arrowhead made of obsidian imported from distant sources was also found at the site. Stephen Thompson

Tens of thousands of years later nothing hints at the tribulations, successes and ingenuity of the ancients that lived here. Along the village paths of what is today land of the Maasai, cows make their way uphill from the river, potato plants in purple bloom sway in the breeze and locals talk about the price of wheat.

The Narok site holds a long record of technological evidence that ranges from the Acheulean, Middle Stone Age to the later Stone Age. This helps in the understanding of technological changes and adaptations that ancients used to overcome environmental constraints and probably thrive.

The closest prehistoric tools that technologically approximate the Narok lower level finds are from the Kapthurin Formation in Baringo, also in Kenya. These date to over 200,000 years. Kapthurin is one of the few well-dated localities that represent a transitional Early to the Middle Stone Age phase.

Yet another possible connection

Further analyses will reveal the true age of the new Narok site. It will also help answer many of Francis Yaipan’s questions: What did they use the tools for? How old are they? How do we know? Did ancient Maasai make them? He also makes his own efforts to find answers.

Yaipan’s unceasing enquiries led to information from a community elder about a cave (enkampune) site near a river. On a cold morning in August we linked up with this elder, a retinue of his neighbours. We all trooped downhill to a wooded pathless area. We end up not at a cave but a rock shelter.

We decided against any excavation. Less that 35 km away is another well-studied prehistoric rock shelter site dating to 40,000 years. It is appropriately named Enkampune ya Muto or “Cave of the river”. As scientists, we are very excited about yet another possible connection.

There is a chance that during the some 130,000 to 5,000 years ago, that prehistoric occupants of this enkampune could have used the upper levels of the Yaipan site 1.5 kilometres away as a workshop. For now we would have to focus our energy, limited time and funds on the Yaipan site upslope.

To get a clearer picture of the site’s context, we collect surface artefacts, fossil remains, soil and volcanic ash samples. We walk in the areas around the site tracing out the different layers of volcanic ash. Two teenaged boys lead the way cautioning us to avoid a thicket where they had sighted leopard cubs the day before. We finally find a quarry still in use that may also have been exploited by prehistoric people at the Yaipan site.

At the end of the expedition, a motley crew of scientists, a US engineer, local newspaper reporter, local farmers, elders and teenage boys had worked together to put together a sketch of the picture of the prehistoric site now christened Yaipan. Preliminary analyses of the finds will be done at Nairobi Museum and Yale University. Comprehensive excavations will likely start in 2017.

Then perhaps we will able to tell the people of the village of Eor Enkitok how far back humans walked this land, how they lived and what the environment was like. Regardless of our future findings, it is indisputable that the cumulative inventions, decisions and choices made by the ancients at Yaipan’s site contributed to our success as human beings.