The versatility that helped humans take over the world emerged very early in our evolutionary history, according to sediments and stone tools from the Olduvai Gorge in Tanzania.
Olduvai provided some of the oldest known tools and fossils of our generation, Homo. A recent study contains evidence of environmental indications buried in the sediment. The results suggest that our early relatives were equipped about 2 million years ago to adapt to new environments.
It seems to have been an important ability to let our family members go worldwide. 1.7 million years ago an early human family member called Homo erectus spread beyond Africa and most of Asia, to Indonesia. They reached Western Europe 1.2 million years ago. During their travels, the hominins experienced many different environments than their ancestors, such as the tropical forests of Indonesia and the arid steppes of Central Asia.
They might have been able to prepare for it by simply staying in one place in Africa. At Ewass Oldupa, a recently excavated site on the edge of the famous Olduvai Gorge, findings indicate that early hominins lived in an ever-changing landscape.
Life after the volcano
The oldest evidence we have for early human relatives at Olduvai Gorge is a handful of stone tools that were manufactured and used about 2.03 million years ago.
Like the other tools excavated at Ewass Oldupa, they are part of the Olduwan complex: relatively simple stone tools made by early hominins such as H. erectus and H. habilis. Olduwan tools are mostly sharp flakes and very basic tools for chopping, scraping and bumping. They are much less complex and precise than the tools later made by hominins, such as Neanderthals, who cut off small flakes of carefully prepared stone cores. But for several hundred thousand years, the rough Olduwan tools did the work.
At Ewass Oldupa it was the survival in a landscape of mostly pigs fern meadows with some grasses and woody plants, irrigated by a meandering river. The ferns were probably the first plants to take root on top of the wide fan pumice stone that had not been sprayed from a nearby volcano too long before. Traces of that landscape still lie buried in a layer of sediment about a meter above the rocky remains of the ancient pyroclastic flow; Paleoanthropologist Michael Petraglia, of the Max Planck Institute for the History of Human History, and his colleagues, along with ten stone tools, found petrified pollen and microscopic pieces of petrified plant tissue called phytoliths.
For hunter-gatherers like H. habilis, of which the fossilized remains were excavated just a few hundred meters from Ewass Oldupa, the fern basin would have been a fairly good place to make a living.
The river provides easy access to water, and the geology of the area has provided several stone resources for tools. Geochemical analyzes of the tools at Ewass Oldupa indicate that hominins here collected their quartzite locally and the rest ventured further up to 12 kilometers away. They seemed to have chosen different materials – in some cases as specific as the choice of slightly different types of quartzite from different angles – for specific tools. (A study last year also suggested that the earliest toolmakers in our family tree know enough to choose their materials wisely.)
But then, as always, everything changes.
New worlds in one place
Thousands of years later, the hominins that once roamed the riverbanks would not recognize the landscape around Ewass Oldupa. The meadow of brackish made way for a patchwork forest and grasslands around the shores of a lake. Microscopic fossils trapped in the sediment indicate that the plant species that make up the forests and grasslands have changed frequently, and charcoal deposits show that veld fires have swept through the area from time to time, helping the patchwork to be rearranged. .
At other points in the long prehistory of the area, the lake has expanded and the muddy sediments of the bank wall indicate a lush landscape of forests and palm trees. The shore later gave way to a dry steppe, mostly bare of trees and grass. Each of these environments offered many different foods, water, supplies, and challenges, but hominins still seem to have returned to Ewass Oldupa.
“Over time, these habitats sometimes changed slowly or rapidly,” Petraglia told Ars. “It is difficult to know how quickly hominins entered new ecosystems due to the resolution of the record, but it is clear that they could handle a wide range of environments.”
Petraglia and his colleagues found stone tools that hominins left behind on the site (probably) H. habilis) on and on during its 200,000 years of continuous change. The 565 stone tools, spread over millennia of layered sediment on the site, do not look like the demolition of a permanent settlement. Instead, hominins seem to have left the sink several times, perhaps due to sudden environmental change or volcanic eruptions, but they kept coming back.
“There were a number of volcanic events within the period of 235,000 years represented at Ewass Oldupa,” Petraglia told Ars. “It is interesting that hominins returned to these areas after each of the eruptions, that is, they never completely left the region.”
Jacks of all trades
And even if the earliest hunters and gatherers at Ewass Oldupa would later find versions of the place completely strange, they would still recognize the tools people used to survive it. For about 200,000 years, hominins relied on the same basic tools to tackle the cliff meadows along the river, the patches of forest and grassland, the lush shore, and the dry porch.
The chopping, scraping and bouncing tools of the Olduwan were relatively simple, but they were also incredibly versatile. According to Petraglia and his colleagues, Olduwan technology offered a basic, general set of tools that could work just as well in a palm grove as on a dry steppe. People have taken over the world because we are generalists, and generalists can adapt almost anything. Our early relatives clearly had the same benefit.
Nature communication, 2020 DOI: 10.1038 / s41467-020-20176 (About DOIs).