In a research yard at the University of Arizona in Tucson, Dan Jeffery can be found studying the reactions occurring inside a 1-meter-tall replica of an ancient iron smelting furnace. The materials science and engineering graduate student is hoping to decipher how these furnaces worked. Since the beginning of the Iron Age, groups such as the Renaissance Europeans, Africans and ancient Romans have used the furnaces to produce iron and steel weapons, tools and armor.
Dan Jeffery of the University of Arizona attempts to recreate the metal mixes that people used long ago, to better understand past people and their cultures. Photo by Lara Lang.
As iron has been an important part of people’s lives for several millennia, understanding how people long ago produced the metal is significant, Jeffery says. But even with today’s technology and a wealth of archaeological excavations and modern engineering data to work with, understanding the operation of these furnaces is far more difficult than it might seem.
“We’re dealing with dead technologies” — tools and toolmaking skills that are no longer in use, says Jim Skibo, an archaeologist at Illinois State University in Normal. Thus, archaeologists have long experimented via trial and error to try to reinvent the tools and technologies, and determine the relationship between ancient people and their objects.
“It’s not easy,” Skibo says. “We’re always trying to make connections between people and the artifacts they left behind,” hoping to figure out not only the basic information — who used a particular site or tool at what time and where — but also how and why those tools came to be.
With his obsolete bloomery furnace, Jeffery is using analytical techniques that take into account physics, kinetics, thermodynamics and geochemistry to determine what combination of temperatures, air flows, types of ore and fuel might create a blend of iron and slag similar to those seen in archaeological evidence. Relatively few well-preserved furnace sites with working debris have been found in the world, Jeffery says, and though written historical accounts mention use of the furnaces for centuries, they do not give many of the important details on the furnaces’ operation.
So he and colleagues combine scientific models with archaeological evidence, such as what resources were known to have existed in a particular area at a specific time period, as well as what remnants archaeologists might have found at a site. Despite several experiments based on the modeling, Jeffery says that he is still a ways away from “successfully” reproducing the process using ancient materials. But the more he experiments, the more he can learn about the technical choices that people made — why they chose a particular raw material or a particular methodology (for example, why African cultures built larger bloomery furnaces than Europeans did, and what that might say about the exploitation of local resources and the social aspects of this technology).
Getting close to understanding what technical choices people made in the past helps to understand their cultures, says Skibo, who teaches a course on prehistoric technologies. “It would be best to have a time machine, but absent that, we’re constantly struggling for answers — squeezing the archaeological record as much as possible for every little drop of knowledge.”
Skibo and several other researchers, for example, have been applying new technologies to learn about ancient pottery-making. “I’ve spent a lot of time thinking about temper,” he says. Temper is what goes into a pot in addition to clay to change the heating properties, and can include anything from sand and shells to blood and hair. Temper, he says, can tell archaeologists a lot about cultures, including settlement patterns, trading partners, and whether the people were citydwellers or hunter-gatherers.
For example, the earliest pottery found in North America dates to about 2000 B.C., and has an organic temper, such as grass or straw. Archaeologists previously thought the organic temper was simply decorative, but, through experiments, have learned that “the best way to make a pot in a day was to add grassy temper,” Skibo says.
Hunter-gatherers such as the early North Americans, he says, would have wanted a quick and easy cooking pot for that evening’s meal. A pot would take longer than a day to make if using a dry temper such as sand. “When we begin to see more sedentary societies, more cities, we begin to see more pots made with dry inorganic tempers,” he says. This is a classic example of how experimental archaeology can make or break theories that may have taken years to develop.
Helen Loney of the University of Glasgow in Crichton, Scotland, says that many analytical techniques can also help determine how pots were used. Researchers have found 2,000-year-old dairy or wine residues in pots, including chemical signatures that may show how ancient people made their wine, or what was in their diets. Xeroradiography, an X-ray process, helps determine how the pots were made. Chemical tests on pottery can show how hot a kiln fire was, and “thus say something of the ability of the potter to control the outcome,” she says. And mineralogical analyses can indicate how the clay was manipulated for specific tasks, such as how the pot may have been used (for cooking versus storage, for example).
“Much of archaeology is based on physical appearance rather than production techniques,” Loney says. But how something is made and used is critical to understanding an individual’s actions so many years ago, she says.
Archaeologists can learn much about a tool’s creation and usage by comparing it to other tools in the record. “Where experiments come in, though, is when we come upon technologies that we don’t know very well,” such as the “flintknapping” process for making stone tools, says George Odell, an archaeologist at the University of Tulsa in Oklahoma, and editor of the journal Lithic Technology.
Flintknapping, a method of knocking one rock against a more brittle one to create a sharp edge, is the oldest documented toolmaking process going back 2 million years, but was almost obsolete by the 19th century. There were anecdotal accounts of the technique, but “sometimes the only way to figure out what people did is for archaeologists to try it themselves,” he says.
For example, archaeologists had been trying to figure out how to flintknap 10,000-year-old stone spearheads found in North America that had a unique design element called fluting, says Robert Dawe, an archaeologist at the Royal Alberta Museum in Edmonton. Many failed attempts by archaeologists to reproduce this shape, he says, resulted in a variety of fanciful interpretations, often using elaborate, complicated lever devices.
The machines did produce the fluting observed on the prehistoric specimens, but were unlike anything described by historical accounts of flintknapping, and therefore unlikely to have been used by early people, Dawe says. Then one day, he says, a strong-handed archaeologist who had mastered the process of flintknapping came along and demonstrated that the fluting could indeed be made by hand. It’s a good example, he says, of how combining experimentation with historical accounts and archaeological evidence provides researchers with better solutions to understand these practices.
“You’re really trying to figure out what’s most probable or most possible,” Odell says. “You’ll never figure out exactly” how the ancients created or used a tool, “but you can get close.” New scientific technologies and partnerships among engineers, materials scientists, geologists, biologists and archaeologists are certainly helping, Jeffery says. Ultimately, he says, learning about the past through tools and technologies helps us to understand how we got to where we are today.
Megan Sever
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