On a recent night at the Argonne National Laboratory in DuPage County, a piece of the world’s newest technology was brought to bear on some of its oldest.
Inside a lead-lined room lay a metal figurine–11 inches tall and 5,000 years old–that represents the dawning of a new age in ancient technology. Learning more about the making of the oldest tin bronze object ever found will help tell the story of some of the earliest human discovery.
Nearby, scientists huddled around a computer screen in a lab attached to Argonne’s billion-dollar, 2-year-old X-ray machine, the Advanced Photon Source. By remote control, the scientists bombarded the figurine with electrons traveling at 99.97 percent the speed of light.
In scanning the figurine, the beam unlocked secrets about the object’s composition and genesis–lessons that could be invaluable in helping the modern world learn about man’s early use of metals.
And by the time the night was over, the scientists present were convinced they had just used the greatest new tool in archeology since the 1949 invention of radiocarbon dating. Within hours, it gave some new insights into the methods of the artisans who made the figurine, people from an advanced but unknown prewriting culture.
Though there are two other photon source rings of similar power in the world, in Japan and France, this was the first time one had been used on archeological material. Until now, the only way to find out more about how the figurine had been made would have been to cut it up and melt it down, something that nobody was willing to do.
As the beam scanned the figurine, an astonished Aslihan Yener said, “Look at that.” Yener, professor at the Oriental Institute at the University of Chicago, insured the figurine for $500,000 to carry it to Argonne for this night of experiments.
The scanning revealed something never known before about the object: In ancient times, its legs had been broken off. Some skilled prehistoric craftsman, obviously knowledgeable about metallurgy, repaired it so perfectly that the break remains hidden to the naked eye 50 centuries later.
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Not only was the break revealed, but the data streaming across the computer screen gave Yener an analysis of the chemical content of the material in each portion of the figurine that it scanned.
“Look at the arsenic,” Yener said in wonderment as the beam crossed the area of the break. “We get arsenic content as we cross the joint. Whatever they used for repairing it was different from the (tin bronze) it is made from.
“Maybe they were using a compound of arsenic, or old (arsenical bronze) scrap metal as a glue, because it had a lower melting point and wouldn’t damage the figurine.
“This is pretty exciting. They were very good metallurgists. This is a new discovery.”
The figurine is tantalizing to scientists because it was made at the same time that humans were discovering a host of new metals.
“When tin started getting mixed with copper, everything else came along with it,” Yener said. “Gold, silver and lead. They all appear about the same date, and we don’t know why, or if it’s all connected.”
The object is called the “naughty figurine” by curators because of its prominent, highly detailed depiction of his manliness. It was one of a group of six figurines, three males and three females, dug up in 1936 by the Oriental Institute’s famed husband-and-wife archeological team, Robert and Linda Braidwood. They were at the bottom of an ancient tell in the Amuq Valley near Antioch (now Antakya), the city of biblical fame in south central Turkey.
The statuettes probably had some sort of ceremonial function, the Turkish-born Yener said. They were elaborately colored, with silver helmets and holding golden spears, and they had sashes of gold around their waists.
Yener will take the figurine back to Argonne this summer to explore its interior structure more thoroughly to find out how it was made.
“We know this figurine was cast but have no idea how it was cast, if it was done in a heated mold, how it was manipulated in the casting to create different colors and so on,” she said. “This new technique should tell us.”
Later this year, Yener will lead a team to Turkey to reopen the excavations where the figurines were found, looking for even earlier artifacts.
“I want to find the formative period of metals and how these guys got to this sophisticated stage,” she said. “Something special was going on at the Amuq Valley at that time.”
Copper was the first metal humans used, and bronze, made by mixing copper with any number of other metals, was the first alloy ever developed. The earliest bronzes were made with copper and arsenic.
The naughty figurine is the first known instance when ancient metallurgists began to use tin instead of arsenic, making bronze stronger and more malleable than before. The tin bronze recipe became useful in art, architecture and weaponry, resonating through human history as the material of choice for church bells and the Liberty Bell. It remains today as the most commonly used bronze alloy.
When Argonne finished the Advanced Photon Source ring two years ago, archeologists saw in it an opportunity to do chemical and physical analysis of highly valued objects without having to take samples from them or damage them.
On the night when scientists analyzed the figurine, electrons traveled through the Photon Source accelerator ring, two-thirds of a mile across, until they raced along at 300,000 laps a second. By creating X-ray beams a million times more powerful than medical X-rays, Argonne physicists were able to aim beams across the surface of the irreplaceable object.
The highly prized time on the ring’s 34 operating beams normally are taken up by all manner of academic and commercial scientists doing bimolecular, chemical, environmental and materials research. Through the University of Chicago, two archeologists negotiated using one beam for two days.
They were Yener and Ben Bronson, Field Museum curator of Asian archeology and ethnology.
Bronson brought in a Japanese samurai sword made in 1760. Scientists are stumped as to how, as early as 600 years ago, Japanese sword makers using primitive technology made a steel harder and tougher than anything modern technology can produce. Bronson said he hoped the Argonne X-rays might offer some answers.
Two Argonne physicists, Dean Haeffner and Esen Ercan Alp, set up the experiments on the archeological objects, starting with the bronze figurine. The payoff was almost immediate.
Bronson was as enthusiastic about the experiment as Yener was, though the Argonne scientists had less time to work on his Japanese sword than they did on her figurine.
“Metallurgists are fascinated by these things,” Bronson said of the sword. “No modern steel can match it for hardness and toughness. We think the secret is the way in which it was constructed, not additives to the steel.”
Bronson brought a sword that he said was of “medium” value for the initial experiments, wanting to be assured that the Argonne machine would not harm the Field Museum’s best swords, worth millions of dollars each.
“I didn’t know if it was worth running the risk, but having seen what these guys can do, we hope to extend this to some very precious objects,” Bronson said. “We have some more important swords we want to do this with now.”
The limited initial experiments went so well, in fact, that scientists from Argonne, the Oriental Institute, the Field and a number of other institutions are going ahead with plans to push for a permanent archeological center at Argonne. They have begun raising $25 million to create the Center for the Study of Ancient Technology and Environment, getting an X-ray beam at Argonne dedicated for that purpose.
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“We’re only beginning to see the tremendous range of possibilities of things we can do with this,” Bronson said.
“This is going to let us see how earliest scientific discovery began. We’re going to learn a lot about pre-modern, non-Western technology.”