The hidden treasures of Olorgesailie


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If you want to know how our ancestors lived 1.2 million years ago, all you need to do is follow the happenings at Olorgesailie prehistoric site, for it is the best dated prehistoric site in the world for that period.  

The gang walk built around the site where many pre-historic bones and tools lay buried. [Credit: Rupi Mangat]

The 300 square kilometre site, on the floor of the Great Rift Valley, an hour’s drive south of Nairobi, has an in-situ museum with prehistoric hand axes as well as sites like the butchery, which was the scene of a hunting expedition believed to have been used by the Homo erectus. It is an amazing place where Dr Rick Potts of the Smithsonian Institute in the USA says, “stone tools keep coming out of the sediments.” 

It’s an important statement since studying the stones tools is like unravelling a book of secrets, or as Dr Potts jokes, “visiting cards left behind.” 

Nobody knows Olorgesailie better than Dr Potts who has been studying the site for the past three decades in collaboration with the National Museums of Kenya (NMK). Each layer of sediment has a story to tell in the history of human evolution. 

The site was first discovered by John Walter Gregory in 1919. Around 1942, it attracted the interest of Kenya’s premier fossil hunters, Louis and Mary Leakey. In 1947, the first African Archaeology Congress was held at which time the gang walk around the stone tool sites was built. 

Present day Olorgesailie is hot, dry and dusty where daytime temperatures hit 40 degrees centigrade. Microscopic plants including fossilised papyrus in the deep layers of sediments reveal periods when a lake existed here, and as it dried out and was covered by layers of dust, it buried a database of plants, tools and bones in it, preserved by the volcanic ash of the two adjacent mountains Mt Esakut and Mt Olorgesailie. Fossils found in-situ include the extinct elephus recki that dwarfs today’s elephant and is genetically closer to the Indian elephant.  

“Hand axes keep rolling out of the sediments,” says Dr Potts at a talk organised by the Kenya Museum Society and the Prehistory Club based at the National Museums of Kenya. “It’s a technology that persisted for 1.5 million years, and was crafted in Africa by the Homo erectus, and spread to Europe and Asia.” 

In the course of his work at Olorgesailie, Potts also became intrigued with the issue of climate change, and how the palaeo-Olorgesailie lake disappeared and re-appeared as the climate changed from cool to hot, and how this influenced the evolution of mammalian species in the region. 

“Olorgesailie is an insight into the fascinating elements of human evolution,” enthuses Potts. 

The Middle Stone Age 

The Olorgesailie sites represent two different times: the hand axe site between 1.2 million to 500,000 years ago, and the Middle stone-age site dated 500,000 years to 100,000 years ago where the sophisticated one-strike flakes are found. It’s a sharp-edged tool – literally a flake – fashioned from one strike on the core stone. It involved precision acquired with practice. 

“But the rock types for the tools were not found locally,” remarks Potts. “They came from sites 150 kilometres away showing an exchange of products between people existed even back then. The Middle Stone age is marked by behavioural innovations like smaller technology, wider social networks and complex symbolic systems. It corresponds with the modern African wildlife. It is notable that not only is Olorgesailie the best-studied site in the world for the period covering the past 1.2 million years ago but it is also the oldest known Middle Stone Age site. 


There have been numerous extinction episodes over millions of years and scientists ponder over why some species like the Homo sapiens (that’s us) have survived from the earliest records 200,000 years to present times while others went extinct like the Elephas recki and the Neanderthal man that lived at the time. 

The adaptability of the genus Homo is amazing given that this species evolved in the past 2 million years during which there has been significant environmental fluctuations. According to fossil research, there are a couple of things that happened in the genus Homo. “There were changes in the brain size,” says Potts. It got bigger and better. At this time, man improved his stone technology, went into the arts with the emerging rock art and symbolism such as burying the dead. 

Life however had its challenges. Extinctions and survival were — and still are — part of the game. Those who survived seem to be the more versatile species like the Homo sapiens whose diet became varied, had a flexible social grouping and began to move greater distances. They became adept at survival. “He planned for contingencies, and we see diversified cultures and many different ways of living,” says Potts. 

Species in this survival-extinction arena like the Neanderthal man confined to small places and extremely adaptive to that habitat became extinct like many modern-day species unable to adjust with the times. 

According to Potts, human survival centres on our adaptability to move to places out of our comfort zone, to thrive in novel environments, to respond to new ways to our surroundings and the ability to modify environments. 

“It’s both creative and risky,” says Potts. “Initially humans made smallscale changes in the environment but today, 83 per cent of the viable land on the planet has been changed by humans. The drama of environmental changes will continue but added in it is the complexity of the modern Homo sapiens influence on it. 

However, human evolution seems at odds with nature. “We have emerged from nature, yet we are at odds with nature,” he says. According to Potts, it’s an area that hasn’t received much attention and makes for more scientific research. 

Even more intriguing is that with our super adaptability and mobility, are we giving rise to another Homo species who will move to outer space? It’s food for thought. 

Author: Rupi Mangat | Source: The East African [November 27, 2011]



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