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A monkey picks up a potato-sized rock in his tiny hands, raises it above his head and smashes it down with all his might on another stone embedded in the ground. As the creature enthusiastically bashes away, over and over, flakes fly off the rock he is wielding. They are sharp enough to cut meat or plant material, but the monkey does not pay much attention to the flakes, save to place one on the embedded rock and attempt to smash it, too. Still, he has unintentionally produced artifacts that look for all the world like stone tools found at some human archaeological sites.

• Stone Tools Made By Early Man

1. Early man invented and created stone and bone weapons and tools. With these tools, early man could kill and trap those animals he needed for food.
2. Pointed Weapons of Wood, Bone, and Ivory: Survival Tools of Early. Early Man quite possibly arrived. And long before he learned to shape bone and chip stone tools.

The monkey is a wild capuchin in northeastern Brazil's Serra da Capivara National Park, where these animals have long been known to use rocks for a wide range of activities, from cracking open nuts and digging for roots to catching the attention of potential mates. Other nonhuman primates, including West African chimpanzees, also use rocks as tools in the wild. But the Serra da Capivara capuchins are the only ones that scientists have seen banging rocks together to break them—an activity previously thought to be exclusive to members of the human family. Humans do it to create sharp-edged tools for cutting things. The capuchins, in contrast, have never been seen using the flakes they make; they just lick the surface of the embedded stone, perhaps in pursuit of mineral dust.

Now a new study has examined the capuchin-produced stone flakes, and it turns out that the chips meet criteria used to distinguish human tools from naturally broken rocks. The findings, published in fall 2016 in Nature, could fuel debate over controversial archaeological sites. The discovery also raises questions about what differentiates humans from other primates and how our lineage started fashioning implements from stone.

The Early Stone Age began with the most basic stone implements made by early humans. These Oldowan toolkits include hammerstones, stone cores, and sharp stone flakes. By about 1.76 million years ago, early humans began to make Acheulean handaxes and other large cutting tools. Explore some examples of Early Stone Age.

Tomos Proffitt of the University of Oxford and a group of his colleagues watched the capuchins select rocks to use as hammers and subsequently strike them against cobbles. The researchers retrieved the fragmented stones and also collected other such artifacts found in excavations within the surrounding area—just as they would if they were excavating a human archaeological site. They then analyzed this collection of 111 capuchin artifacts, examining their shapes and sizes, as well as the nature of the scars left on the rocks by all the bashing. Download adventureworks 2012 db.

Stone Tools Made By Early Man

Remarkably, the team found that the capuchin artifacts exhibit distinctive scoop-shaped, or “conchoidal,” flaking and sharp edges and that the monkeys often removed multiple flakes from a single rock—all hallmarks of man-made stone tools. (The authors note that stone fragments produced during chimpanzee nut cracking, in contrast, lack most of the diagnostic criteria, as do flakes produced by captive bonobos that have been taught to knap.)

Experts have previously linked such characteristics to the emergence of humanlike hands and coordination and to shifts in human cognition. But the fact that monkeys produced rocks with these same traits demands a different evolutionary explanation. And if modern-day monkeys modify rocks in this way, it is possible that extinct monkeys and apes did, too, leaving behind archaeological assemblages of their own. Archaeologists thus need to refine the criteria they use to identify stone tools intentionally produced by members of the human family, Proffitt and his colleagues argue.

“Many people are going to be disturbed that these tools can be made by capuchins,” says archaeologist Sonia Harmand of Stony Brook University, who was not involved in the new research. According to Harmand, the monkey artifacts would not look out of place at East African sites containing tools made by human ancestors in one of the earliest technological traditions: the Oldowan, which dates back to 2.6 million years ago at the site of Gona in Ethiopia. The capuchin flakes resemble the simplest examples of Oldowan technology. But other Oldowan stone tools exhibit considerably more sophistication and planning, she says. The monkey artifacts also diverge from the oldest known stone tools in the world: 3.3-million-year-old implements that Harmand and her team excavated from the site of Lomekwi in Kenya. The Lomekwi tools are far larger and are made of basalt and phonolite—rocks that are denser than the quartz and quartzite rocks the capuchins use.

Some experts wonder whether the capuchins' flakes could spark doubts that members of the human lineage made the oldest stone tools. Although researchers have attributed the tools to human ancestors, the sites lack diagnostic fossils to establish the connection. “We have no clue” who created the material at Lomekwi and Gona, says archaeologist Wil Roebroeks of Leiden University in the Netherlands. Hélène Roche of Paris West University Nanterre La Défense disagrees, writing in a commentary accompanying the Nature paper that the capuchin findings should not raise suspicions about who produced the early stone tools found in Africa. Archaeologists have studied hundreds of those sites, she notes—and many of them contain contextual clues, including cut-marked bones that show how tools were used, as well as fossils that indicate human ancestors made them.

Although the capuchin discovery demonstrates that nonhuman species can accidentally produce fragments of rock that look just like human-crafted cutting tools, that does not mean the man-made tools are not special, Harmand cautions. Even if human ancestors started creating flakes unintentionally like the capuchins do, there was something that made them realize they could put them to use and even make new tools to suit their purposes. Moreover, human technology evolved from the comparatively simple tools seen at Lomekwi and at Oldowan sites to hand axes with carefully shaped cutting edges a million years later and eventually to the elaborate machinery we have today. Why did technology fail to evolve to the same degree in chimps and monkeys? Harmand asks. Why did humans alone take it to such an extreme?

Proffitt is eager to determine how long capuchins have been using rocks this way. Other evidence demonstrates that they have been using the cobbles to crack open nuts for at least 600 years. And chimpanzee stone tools from the Ivory Coast in West Africa date back to 4,300 years ago. Beyond that, “we have no evidence of what ancient monkeys or great apes were doing,” Harmand observes—which leaves plenty of room for more surprises in the future.

reader comments

For at least 2.6 million years, humans and our ancestors have been making stone tools by chipping off flakes of material to produce sharp edges. We think of stone tools as very rudimentary technology, but producing a usable tool without wasting a lot of stone takes skill and knowledge. That's why archaeologists tend to use the complexity of stone tools as a way to measure the cognitive skills of early humans and the complexity of their cultures and social interactions.

But because the same tool-making techniques didn’t show up everywhere early humans lived, it’s hard to really compare how stone tool technology developed across the whole 2.6 million-year history of stone tool-making or across the broad geographic spread of early humans. To do that, you’ve got to find a common factor.

So a team led by anthropologist Željko Režek of the Max Planck Institute for Evolutionary Anthropology decided to study whether the length of the sharp, working edge of stone flakes changed over time relative to the size of the flakes. A longer, sharp edge is more efficient and takes more control and skill to create, so Režek and his colleagues reasoned that it would be a good proxy for how well early humans understood the process of working stone and how well they shared that knowledge with each other.

A quick lesson in stone knapping

When you’re trying to knock a sharp flake off a chunk of stone, the size of the flake and the length of its edge depend on how and where you strike the stone core.

“Stone artifacts vary greatly in complexity, but the physics of stone knapping mean that the most fundamental part of the process of their creation—flake detachment—is similar whether one is producing a single large sharp flake to help butcher an animal or putting the finishing touches to a microlithic weapon component,” wrote University of Bordeaux archaeologist Natasha Reynolds in a comment on Režek’s study.

One of the most important factors is the thickness of the flake at the spot where it starts (called the platform depth). Another is the angle between the surface being hit to create the flake and the surface of the stone core that the flake breaks off from (called the exterior platform angle). A larger exterior platform angle will create a flake with a long edge relative to its size. But getting it right takes planning, skill, and knowledge.

“Controlling these two variables when making a flake requires an ability to direct force at a precise location for a given platform angle,” wrote Režek and his team. “This is a skill that is uniquely human.” And that, they say, means that the length of a flake’s working edge can reveal something about the skill of its makers. That, in turn, can offer clues about how hominin cultures advanced and passed along new skills over the last 2.5 million years.

So Režek and his colleagues measured the edges of more than 19,000 stone flakes from 81 groups of artifacts from sites in Africa, southwest Asia, and Western Europe, spanning a stretch of human history from Homo habilis 2.6 million years ago to modern humans 12,000 years ago. Those sites contain artifacts from at least five hominin species: H. habilis, H. erectus, H. heidelbergensis, Neanderthals, and modern humans.

Edges get longer, but also more diverse

Throughout the Pleistocene, the average length of working edges increased relative to flake size. Early Pleistocene stone flakes, made by H. habilis and H. erectus before about 1 million years ago, had the shortest working edges in the study. After about 1 million years ago, though, flake edges started getting longer, and it appears that H. erectus, followed by H. heidelbergensis and Neanderthals, learned how to control platform depth and exterior platform angle in order to get more sharp edges relative to the size of their flakes.

That trend continued with modern humans, but at the same time, edge length also started to vary more from site to site. Modern humans living after about 50,000 years ago produced the flakes with both the longest and the shortest sharp edges for their size. It looked as if humans had learned how to make more efficient flakes, but they didn’t always put that knowledge to work.

But that variation may actually be a sign of technological progress for early humans.

Being able to get a longer-edged flake out of a single strike is a really efficient use of stone, which gives you an advantage when you’re short on resources or when you have to carry a stone a long distance to work or use it. But there are other ways to make sharp edges—for instance, the small, sharp bladelets from the Upper Paleolithic at Abri Pataud cave shelter in France have very short edges but clearly demonstrate sophisticated, efficient craftsmanship.

Meanwhile, the same precision and skill that allowed production of longer edges also allowed toolmakers to vary their edge length for techniques like Levallois or for making short bladelets. Comparing the length of sharp flake edges still offers a good window into the development of the control and skill necessary to do it.

And sometimes a sharper edge wasn’t the answer. “The production and use of projectile tools was critical in some contexts, while in others, simple thick flakes may have represented a selective advantage,” Režek and his colleagues wrote.

The ability to adapt technique to context is actually pretty sophisticated, and that may be what’s behind the increase in variation among flake edges over time. Looking broadly at all these sites, it appears that human culture got better at producing sharp stone flakes over time, even as hominins apparently learned to vary the results as needed.

More questions to answer

Režek’s findings generally support what archaeologists have understood for years about the general trend toward skill and complexity in early human technology, but it’s one of the first studies comparing large numbers of artifacts across so much time and distance. Edge length gives archaeologists a standardized, concrete way to look at the big picture of human cultural evolution, which has been one of the biggest challenges for Paleolithic archaeologists so far.

If archaeologists can find ways to apply that method to other aspects of stone tool making or in other geographic areas, that could help them tackle some big-picture questions about the development of human culture and cognition.

Full album youtube. “It would be interesting to know how these trends hold up when more data are included, for example from early Neanderthals with systematic blade production or more of the varied assemblages associated with anatomically modern humans in North Africa,” wrote Reynolds. “It would also be interesting to consider Holocene knapped lithic assemblages, including those from Australia and the Americas.”

Nature, 2017. DOI: 10.1038/s41559-018-0488-4 (About DOIs).