1. Early Stone Tools Were Developed About

Recreating Early Tools. Homo habilis Toth has made stone tools similar to those used by early man and used them to butcher an elephant that had died of natural causes. The flaked flint ax easily cut through the centimeter thick hide. The tools at this site are so well made, requiring such precision, that the anthropologists suspect that by 2.6 million years ago hominids had been making stone tools for thousands of years. Jan 12, 2018 - Hammerstones are some of the earliest and simplest stone tools. Prehistoric humans used hammerstones to chip other stones into.

Approximately 3.3 million years ago someone began chipping away at a rock by the side of a river. Eventually, this chipping formed the rock into a tool used, perhaps, to prepare meat or crack nuts. And this technological feat occurred before humans even showed up on the evolutionary scene.

That’s the conclusion of an analysis published today in Nature of the oldest stone tools yet discovered. Unearthed in a dried-up riverbed in Kenya, the shards of scarred rock, including what appear to be early hammers and cutting instruments, predate the previous record holder by around 700,000 years. Though it’s unclear who made the tools, the find is the latest and most convincing in a string of evidence that toolmaking began before any members of the Homo genus walked the Earth.

“This discovery challenges the idea that the main characters that make us human—making stone tools, eating more meat, maybe using language—all evolved at once in a punctuated way, near the origins of the genus Homo,” says Jason Lewis, a paleoanthropologist at Rutgers University and co-author of the study.

Up until now, the earliest clear evidence of stone tools came from a 2.6-million-year-old site in Ethiopia. An early human ancestor called Homo habilis likely made them. Similar “Oldowan style” tools, known for choppers with one refined edge, have been discovered at several other sites in East and Southern Africa.

The common assumption has been that as Africa’s climate changed and forest canopies gave way to savannas, early hominins diversified and the Homo genus—the line that would produce modern humans—emerged, around 2.8 million years ago. With new environments came new food sources and a need for tools to process those foods. Grassland may have provided ample sources of meat, plants and nuts, while the forest provided shade and cover to prepare them.

But scientists have started to poke holes in that line of thinking. In 2010, researchers found fossilized animal bones in Kenya dating to 3.4 million years ago with cut marks on them—possibly made from a stone tool, though still controversial. Australopithecus afarensis (Lucy’s species) was the only human ancestor or relative around at the same time and place. Another hominin, Australopithecus africanus, appears to have had a grip strong enough for tool use. Studies show chimpanzees use rocks as hammers or anvils on their own in the wild, and, with a little guidance, bonobos are capable of creating stone tools.

Back in July of 2011, Lewis teamed up with his wife and co-author Sonia Harmand, an archaeologist at Stony Brook University, to lead a field expedition in Kenya for the West Turkana Archaeological Project. They were looking for artifacts similar in age to a controversial 3.5 million-year-old species discovered by Meave Leakey’s group years earlier.

But, the survey team took a wrong turn and ended up at a site now called Lomekwi 3 in dried river ravine. “To us it was immediately a very interesting area,” notes Harmand, “with outcrops and erosive cuts, you could see what was normally hidden by the sediment.” So, they spread out and started looking.

Just after teatime, a radio call came in: Someone had spotted a series of strange stones sticking out of the sediment. Scars cut into the stones set them apart from run-of-the-mill rocks. “You can tell these scars are organized,” says Harmand. The rocks had been hit against one another to detach flakes, a process called knapping. Based on geological records for the area, the artifacts had to be at least 2.7 million years old. “We had no champagne that evening, but we were very happy,” Harmand recalls.

As it turned out, the 149 artifacts eventually excavated from the site were even older. Analyses of magnetic minerals and volcanic ash tufts imbedded in the local rocks put the age of the stones at 3.3 million years.

“I've seen the altered rocks, and there is definitely purposeful modification of the stones by the hominins at the Lomekwi site 3.3 million years ago,” says paleoanthropologist Rick Potts, director of the Smithsonian’s Human Origins Program, who was not affiliated with the study. Potts notes that while the study is exciting, it also raises a lot of big questions.

Among them, how are these new artifacts related to the Oldowan tools? The short answer is no one knows. “We've jumped so far ahead with this discovery, we need to try to connect the dots back to what we know is happening in the early Oldowan,” says Harmand.

What’s perhaps most intriguing about the Lomekwi tools is who made them, why and how.

Further analysis of the markings on the tools and attempts to replicate their production suggests two possible ways: The toolmaker might have set the stone on a flat rock and chipped away at it with a hammer rock. Or, the toolmaker could have held the stone with two hands and hit it against the flat base rock. “It’s very rudimentary,” says Harmand.

(The early humans who made the Oldowan tools used an entirely different method: putting a rock in each hand and striking them together with just the right force at just the right angle—which would have required more dexterity.)

As for who, the species identified by Meave Leakey’s group, Kenyanthropus platyops, is a prime suspect. If that’s true, or if the Lomekwi tools were made by another species outside the human genus, some of the same factors that drove our evolution might also have driven the evolution of other distant cousins.

But, Lewis and Harmand aren’t ruling out the possibility that an unknown member of the human genus once inhabited the area and made the tools. “That's a different but equally interesting story, in which our genus evolved half a million years before, and in response to completely different natural selective pressures, than we currently think,” says Lewis.

Whoever made these tools was somehow motivated to hit two rocks together. Why exactly remains a mystery.

A hammerstone (or hammer stone) is the archaeological term used for one of the oldest and simplest stone tools humans ever made: a rock used as a prehistoric hammer, to create percussion fractures on another rock. The end result is the creation of sharp-edged stone flakes from the second rock. Those flakes can then be used as ad hoc tools, or reworked into stone tools, depending on the technical skill and knowledge of the prehistoric flint knapper.

Using a Hammerstone

Hammerstones are typically made from a rounded cobble of medium-grained stone, such as quartzite or granite, weighing between 400 and 1000 grams (14-35 ounces or .8-2.2 pounds). The rock which is being fractured is typically of a finer-grained material, rocks such as flint, chert or obsidian. A right-handed flintknapper holds a hammerstone in her right (dominant) hand and bangs the stone on the flint core in her left, making thin flattish stone flakes come off the core. This process is sometimes called 'systematic flaking'. A related technique called 'bipolar' involves placing the flint core on a flat surface (called an anvil) and then using a hammerstone to smashing the top of the core into the anvil's surface.

Stones aren't the only tool used to turn stone flakes into tools: bone or antler hammers (called batons) were used to complete the fine details. Using a hammerstone is called 'hard hammer percussion'; using bone or antler batons is called 'soft hammer percussion'. And, microscopic evidence of residues on hammerstones indicates that hammerstones were also used to butcher animals, in particular, to break animal bones to get at the marrow.

Evidence of Hammerstone Use

Archaeologists recognize rocks as hammerstones by the evidence of battering damage, pits and dimples on the original surface. They aren't typically long-lived, either: an extensive study on hard hammer flake production (Moore et al. 2016) found that stone hammers used to strike flakes from large stone cobbles cause significant hammerstone attrition after a few blows and eventually they crack into several pieces.

Archaeological and paleontological evidence proves that we've been using hammerstones for a very long time. The oldest stone flakes were made by African hominins 3.3 million years ago, and by 2.7 mya (at least), we were using those flakes to butcher animal carcasses (and probably wood-working as well).

Technical Difficulty and Human Evolution

Hammerstones are tools made not just by humans and our ancestors. Stone hammers are used by wild chimpanzees to crack nuts. When chimps use the same hammerstone more than once, the stones show the same kind of shallow dimpled and pitted surfaces as on human hammerstones. However, the bipolar technique is not used by chimpanzees, and that appears to be restricted to the hominins (humans and their ancestors). Wild chimpanzees do not systematically produce sharp-edged flakes: they can be taught to make flakes but they do not make or use stone-cutting tools in the wild.

Hammerstones are part of the earliest identified human technology, called the Oldowan and found in hominin sites in the Ethiopian Rift valley. There, 2.5 million years ago, early hominins used hammerstones to butcher animals and extract marrow. Hammerstones used to deliberately produce flakes for other uses are also in the Oldowan technology, including evidence for the bipolar technique.

Research Trends

There has not been a lot of scholarly research specifically on hammerstones: most lithic studies are on the process and results of hard-hammer percussion, the flakes and tools made with the hammers. Faisal and colleagues (2010) asked people to make stone flakes using Lower Paleolithic methods (Oldowan and Acheulean) while wearing a data glove and electromagnetic position markers on their skulls. They found that the later Acheulean techniques use more diverse stable and dynamic left-hand grips on hammerstones and fire up different parts of the brain, including areas associated with language.

Faisal and colleagues suggest this is evidence of the process of evolution of motor control of the hand-arm system by the Early Stone Age, with additional demands for the cognitive control of action by the Late Acheulean.

Sources

This article is part of the About.com guide to Stone Tool Categories, and part of the Dictionary of Archaeology

Ambrose SH. 2001. Paleolithic Technology and Human Evolution. Science 291(5509):1748-1753.

Eren MI, Roos CI, Story BA, von Cramon-Taubadel N, and Lycett SJ. 2014. The role of raw material differences in stone tool shape variation: an experimental assessment.Journal of Archaeological Science 49:472-487.

Early Stone Tools Were Developed About

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