Archaeology and robotics don’t typically go hand in hand, but the team of researchers in Harold Dibble’s lab rely on one every day. It’s affectionately called Super Igor, a moniker earned from its status as the more powerful version of the first iteration, Igor, that joined the lab in the early 2000s.
Super Igor is a hydraulic-powered machine that can produce up to 20,000 pounds of force, and in the setting of Penn’s Laboratory for the Study of Ancient Technology (LSAT), it allows Dibble and his team to test with pinpoint precision how early humans might have made stone tools and flakes, from as far back as 2 million years ago to as recently as 10,000 years ago. They can examine in a completely controlled setting which variables affect how these implements were fashioned, as well as investigate how much influence factors such as source material—obsidian versus basalt, for instance—had on the process.
In the decade-plus since LSAT began, Dibble and colleagues have made some important contributions to the field. Most recently, a March 2018 Nature Ecology & Evolution paper set forth a methodological breakthrough in the way scholars think about stone tools, flipping on its head which pieces actually represent “finished” products. It also chronicled for the first time the evolution of these tools.
Specifically, Dibble’s latest work showed that at the inception of such tool-making, people started with a single method that resulted in just one kind of clunky tool. The techniques and end products improved until our ancestors arrived at more varied, effective implements. The findings paint a new story about how these artifacts helped people spread into novel environs.
“The world consists of a lot of different environments, many different situations, and this is a cog in understanding what allowed us to, in effect, inhabit a diversity of places.” Archaeologist Harold Dibble
“The variability reflects an increased flexibility on the part of humans to adapt to different circumstances,” Dibble says. “It’s not like there was a moment in the past where people said, ‘If I make tools this way, we’ll be able to colonize the world.’ The world consists of a lot of different environments, many different situations, and this is a cog in understanding what allowed us to, in effect, inhabit a diversity of places.”
George Leader, a postdoctoral fellow who has worked with Dibble for three years, describes the findings as a way to finally equate like with like.
“Early on our hominid ancestors were basically breaking rocks to get a sharp edge. They used that edge for cutting, scraping, whatever they needed. But 50,000 years ago, they’re making gorgeous points that are 20 centimeters long, perfectly symmetrical, retouched, attached to a spear,” he explains. “Comparing a broken rock to this beautiful spear point is impossible unless there are certain similarities, and you find those in how they’re made, the platform depth, the external platform angle, the angle of the blow, aspects we can see from beginning to end.”
That Dibble, Leader, and the others in the lab—postdoctoral fellow Tamara Dogandžić and graduate students Aylar Abdolahzahdeh and Li Li—can even offer such forward-thinking assertions shows a complete shift in thinking for the field.
Imagine for a moment a “stone tool.” Perhaps an arrowhead-shaped object comes to mind, paperweight-sized, large and heavy, with enough mass to make an impact when thrust or thrown. Archaeologists previously held that such implements were the goal, the tools early humans had intended to create through a process called flintknapping, which Dibble likens to sculpting. “You remove little pieces called flakes,” he says. “You make a hammer out of rock or bone or antler, and you strike the stone to remove a flake.” The sculptor chips off more and more flakes until the envisioned shape emerges.
The problem is, dig after dig has uncovered far fewer of this prize than scientists would have expected. Dibble himself has excavated 10 sites, amassing some 150,000 artifacts; more often than not only 1 percent of findings from a field site would resemble the completed stone tool described above. The rest would comprise fragments or flakes—always just thought of as waste. The phenomenon got the Penn archaeologist thinking, and he brought the question back to the nascent LSAT and its newest teammate, the custom-built Igor, which could mount and strike different source materials at varying angles and depths.
“We started at the basics. We knew going in that there were many variables that flintknappers could control, but we didn’t know how each actually affected the flakes,” Dibble says. “We found a lot of things people hadn’t realized were happening. It’s like any complex motor skill; you may think you know what you’re doing but it’s so internalized. You do it without thinking.”
Dibble’s lab is unique in that the researchers can actually control each element, rather than, say, dropping ball bearings on a piece of glass to see what happens. “Usually as archaeologists, we try to do things ourselves, like survivalists. We’ll try to make fire this way or stone tools that way. We recognize which variables and actions are important, but we’re never able to objectively evaluate what it is that actually makes a difference,” Dogandžić says. “This control setting offers the opportunity to see what it is exactly that is affecting the outcome.”
So far, the team has tested a wide range of actions that a flintknapper can vary when removing flakes with specific characteristics. They’ve proven that results generated from glass, which previously had been used almost exclusively to do most of their experiments, apply to many other materials used in the past, and they’re expanding what they plan to test, adding quartzite and andesite to a list that already included obsidian, basalt, and flint. In the future, they’d like to investigate what heating does to raw material and how early humans made very large objects.
Super Igor as lab mate opens up the universe of questions these scientists can ask.
“Archaeologists basically deal with people’s garbage,” Dibble says. “If you go down to Ben Franklin’s house, you’re not going to find his treasures. You find what he discarded. We’re not digging up treasures—but what you’re left with is something that has gone through a number of stages.”
And that progression, in and of itself, tells a fascinating story, Leader adds.
It might not be so obvious when you’re talking about broken rocks, but the bigger picture is that we see social traditions building over those millions of years. George Leader, postdoctoral fellow in Dibble’s lab
“If we understand how humans have transmitted knowledge for 2 million years, it’s relevant to how we transmit knowledge today. It might not be so obvious when you’re talking about broken rocks, but the bigger picture is that we see social traditions building over those millions of years,” he says. “How big a role did stones play in the life of early hominids? Were they using them every single day or once a month? It’s really tough to say, but stone lasts and where it’s left, it stays looking like the day it was broken or the day it was left. And that’s what we use.”
Harold Dibble is the Francis E. Johnston Term Professor of Anthropology in the Department of Anthropology in the School of Arts and Sciences.
George Leader is a visiting scholar in the Department of Anthropology.
Tamara Dogandžić is the Marie Skłodowska-Curie Research Fellow in the Department of Anthropology.
Photo at top: Postdoctoral fellows Tamara Dogandžić and George Leader prepare Super Igor, a hydraulic-powered machine that can produce up to 20,000 pounds of force, allowing the research team to test how early humans might have made stone tools and flakes.
Homepage photo: Harold Dibble and his team research how humans might have made stone tools and flakes, from as far back as 2 million years ago to as recently as 10,000 years ago.
