Ancient humans went the extra mile (literally) for quality stone tools

By Stephen Beech

Man's ancestors transported stones over long distances to craft tools 2.6 million years ago - 600,000 years earlier than previously thought.

Stone tools unearthed in Kenya reveal that hominins regularly moved raw materials up to eight miles, say American scientists.

Research shows that ancient humans used an array of stone tools - known collectively as the Oldowan toolkit - to pound plant material and carve up large prey, such as hippopotamuses, In southwestern Kenya more than 2.6 million years ago.

The "durable and versatile" tools were crafted from special stone materials collected up to eight miles away, according to the new study published in the journal Science Advances.

The international research team says their findings push back the earliest known evidence of ancient humans transporting resources over long distances by some 600,000 years.

Study senior author Dr. Rick Potts, of the Smithsonian Institution Museum of Natural History in Washington, DC, said: "People often focus on the tools themselves, but the real innovation of the Oldowan may actually be the transport of resources from one place to another.

“The knowledge and intent to bring stone material to rich food sources was apparently an integral part of toolmaking behavior at the outset of the Oldowan.”

The research team analyzed stone tools uncovered on Kenya’s Homa Peninsula, a fossil-rich region that juts out into the eastern margins of Lake Victoria.

Dr. Potts first surveyed the region’s fossil sites in 1985, and has worked closely since then with colleagues at the National Museums of Kenya to excavate the area’s gullies.

He explained that one of the peninsula’s most significant sites is known as Nyayanga and contains archaeological finds dating back some three million years.

A series of recent excavations yielded a trove of stone tools and hundreds of butchered hippopotamus bones.

In an earlier paper, the research team suggested that the bones represent the oldest known evidence of ancient hominins using stone tools to butcher large animals.

Co-author Professor Thomas Plummer, of Queens College, City University of New York, said: “Hominins were using stone tools for a variety of pounding and cutting tasks, including processing plant and animal foods and working wood.

“The diversity of activities that used stone tools suggests that even at this early stage of cultural development, stone tools enhanced the adaptability of the hominins using them.”

The researchers say the development of the Oldowan toolkit made it possible for early humans to consume large prey.

Around three million years ago, ancient hominins began refining their toolmaking, using hammerstones to strike stone cores and create sharp-edged flakes.

By pounding, slicing and scraping, the stone tools could process and refine a greater variety of plant and animal materials.

The researchers say that finding the right rocks was vital as Oldowan tools needed to be fashioned from stones that were strong yet brittle enough to easily flake.

But the local rocks at Nyayanga are relatively soft, and would produce cutting tools that would quickly dull and pounding tools that would be more likely to shatter.

Like using a flimsy plastic knife trying to cut through a well-done steak, the researchers say those stones would have been of little use for pounding tough plants or breaking animal bones.

As a result, hominins at Nyayanga appear to have brought in stronger stones from other areas.

The research team analyzed the geochemistry of hundreds of stone cores and flakes found at Nyayanga that date back at least 2.6 million years.

They discovered that these tools were crafted from volcanic rocks such as rhyolite and metamorphic rocks like quartzite.

The team surveyed local geology and discovered that those rock types were common in drainage basins several miles east of the Homa Peninsula.

The researchers say the Nyayanga stones are "significantly older" than other known examples of ancient stone transport.

Previously, the oldest evidence of hominins moving rocks over significant distances was a two-million-year-old site known as Kanjera South that is also located on the Homa Peninsula.

Study co-author Dr. Emma Finestone, of the Cleveland Museum of Natural History, said: "It’s surprising because the Nyayanga assemblage is early in the Oldowan and we previously thought that longer transport distances may have been related to changes that happened in our more recent evolutionary history."

Dr. Potts says the ability to transport resources is a "major milestone" in human evolution as it shows ancient hominins’ ability to plan ahead and assess the requirements for processing food.

He said it also illustrates an ability to mentally map their environment and remember locations with high-quality rocks.

Dr. Potts added: “The mental maps of the oldest known hominins to persistently make stone tools well surpassed their immediate surroundings, even surpassing a few miles."

At the oldest hippo butchery site, the team found a molar tooth from a hominin in the genus Paranthropus, a group that sported strong skulls and teeth to grind tough material.

Another Paranthropus tooth was found nearby on the surface of the same geological bed.

The existence of Paranthropus teeth alongside Oldowan stone tools suggests that those hominins may have used stone tools like their close evolutionary relatives in the genus Homo.

However, the case is far from closed.

Dr. Finestone said: “Unless you find a hominin fossil actually holding a tool, you won’t be able to say definitively which species are making which stone tool assemblages.

“But I think that the research at Nyayanga suggests that there is a greater diversity of hominins making early stone tools than previously thought.”

She says the artifacts at Nyayanga also underscore that ancient humans have transported raw materials to fuel technological innovations for millions of years.

Dr. Finestone added: “Humans have always relied on tools to solve adaptive challenges.

“By understanding how this relationship began, we can better see our connection to it today - especially as we face new challenges in a world shaped by technology."