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Archaeology From Reel to Reel - A Special Report
Photograph of hat and bullwhip
X Never, Ever Marks the Spot - Indiana Jones and the Last Crusade
A hominid skull with teeth in place.
Using Lasers to Check Ancient Teeth for Clues to Human Evolution
A hominin skull with teeth in place.

Credit: Reprinted with permission from AAAS

For Indiana Jones, his various allies and his rivals, the keys to the past lie in a variety of repositories, some more mundane than others.

Some are as commonplace as a compilation of clues kept in a handwritten diary that eventually lead to the resting place of the Holy Grail. Others are as exotic as the headpiece of a staff inscribed with instructions for building a decoder that, when used in just the right place at just the right time, allows you to find just the right place to dig for a lost treasure (provided, of course, you have the whole inscription).

Sometimes even a tiled floor is where "X", literally, marks the spot.

But never in the course of three—and soon to be four—feature films did scraping a tooth lead Jones to riches and rewards or even to solve scientific mysteries literally millions of years old.

While likely he couldn't vouch for the riches, Matt Sponheimer, an NSF-funded bioarchaeologist at the University of Colorado at Boulder, argues that the intellectual effort of analyzing the chemical make-up of the teeth of early human ancestors has struck scientific pay dirt.

Matt Sponheimer, an NSF-funded bioarchaeologist at the University of Colorado at Boulder, argues that the intellectual effort of analyzing the chemical make-up of the teeth of early human ancestors has struck scientific pay dirt.

"What is truly surprising is that we may be able to discover how creatures moved across African landscapes 1.8 million years ago using this technique," he said.

Of course Sponheimer, who seems quite familiar with the Indiana Jones saga, would be the first to concede that Jones would have been greatly hampered, even if he'd wanted to try this kind of thing because the laser, which is central to Sponheimer's work, was not yet even so much as a ruby-red gleam in scientists' eyes early in the 20th century, when the films are set.

"That, to me, is the story," he says. "It's not so much about the early results, but what they reveal about the potential of the technique. Indie would have been in this classroom saying that speculations about such ancient behaviors are not part of archaeology, because they're not based on fact."

Sponheimer, on the other hand, may help to change dramatically, science's view of how early humans spent their lives with information stored in fossilized teeth from the dawn of time. It is both a technological and archaeological challenge.

"Essentially what you're doing is analyzing the isotopic composition of these teeth," he says.

Upon reflection, he pauses and simplifies, "What we're doing is shooting the teeth with a laser beam that removes the tiniest bit of material, material that is more or less invisible to naked eye."

And that's what he studies.

Contained in the material that the laser pares away are strontium isotopes, or different forms of the element strontium, a chemical found in plants. The particular isotopes present in plants match up to the particular geographic location where the plants thrived and, most important, were also absorbed into the developing teeth of a young animal that ate the plants.

Because tooth formation takes place early in an animal's life, it is possible to compare where animals ranged when they were young to where the teeth were recovered when they died.

And because the new technique causes minimal damage to teeth and early hominin teeth are so rare ("They're a hell of a lot rarer than diamonds," Sponheimer notes), the laser sampling is an important advance over prior methods that caused significant damage to the fossilized rarities.

Comparing isotopic maps made in the field in Africa with the isotopic compositions of fossilized teeth in South Africa's Transvaal Museum has allowed Sponheimer and colleagues to investigate migration patterns and other behaviors of these important human evolutionary relatives for the first time.

Except for modern-day Homo sapiens, the hominins are extinct.

But, scientists believe that understanding hominin behavior is essential to understanding the path of human evolution. Land-use and movement patterns are essential to such studies, but have historically been almost impossible for anthropologists to track, millions of years after the fact.

The findings from the strontium isotope analysis suggest that most of the hominins spent their early lives in the same geological area on which they died, and probably did not move great distances.

They may also shed light on the long-debated question of whether or not these hominins followed a pattern similar to that of today's chimpanzees, where males stay with their social groups and females find homes elsewhere. The initial results are intriguing, he says, but he's not ready to reveal them quite yet.

"We'll be publishing these results soon, and we're all entitled to a bit of mystery, however short-lived," he says.

What makes this so important to the field, Sponheimer adds, is that it may ultimately provide physical evidence to support a previous conjecture, one way or another. "In the past, there was no window into this kind of behavior," he notes. The new technique "opens that window to behaviors that we simply could not investigate in the past."

Such great leaps forward in technology and in scientific techniques have changed the archaeological landscape forever so that we can now answer questions that early archaeologists, including the fictional Indiana Jones, would have considered insoluble, he says.

"Unlike Indiana, we don't have whips and guns," Sponheimer points out. "But we have an archaeological record out there. It's got a story, we have to learn to make it speak and we have this tool, which is science, to do that. We can now answer questions that would have been relegated to the fantasy bin years ago."
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