Tuesday, Dec. 28, 1999

Chronology key to archaeology, scientist asserts

By Mike Lee Herald staff writer

BOULDER, Colo. - Tom Stafford's laboratory - stacked with mastodon teeth, saber-tooth cat legs and bat jaws - is the backbone of modern scientific attempts to understand the past.

"Archaeology is nothing without chronology," said Skye Sellars, a geochemist at Stafford Research Laboratories, one of the top radiocarbon-dating labs in the nation.

Despite repeated requests by the Department of the Interior, lab founder Stafford declined this fall to date Kennewick Man's bones. He feared government lawyers would bend his conclusions to fit their case ratherthan follow the dictates of science and publish his complete report.

"They would have selected out what they wanted to know," he said. "Their goal is to win an argument. My goal is to find truth by scientific experiments.

"Science would be at odds with the law."

Three other laboratories accepted Kennewick Man - Beta Analytical in Miami, the University of California at Riverside and the University of Arizona in Tucson. Three of the four samples dated took much longer than expected to process because pieces of Kennewick Man that were selected by the government turned out to be very low in protein, the requisite for carbon dating.

Carbon dating isn't simple even under the best circumstances.

"The dating of bones is an enormous hassle," Stafford said. "There's innumerable problems, innumerable errors."

Radiocarbon dating resulted from nuclear bomb development at the University of Chicago, where Willard Libby determined atomically unstable carbon 14 had a half-life of 5,568 years, long enough to be useful for archaeology. Half-life is the time it takes for half of an element to disappear.

Libby won the 1960 Nobel Prize in chemistry for his work. "When radiocarbon dating was developed, it revolutionized archaeology because it enabled (scientists) to ... build a more accurate picture of the human past," said Tom Higham, deputy director of the University of Waikato Radiocarbon Laboratory in New Zealand, who operates a radiocarbon Internet site.

Radiocarbon works because plants take in carbon dioxide through photosynthesis and animals consume carbon-carrying plants. Thus, carbon continues to increase in living things until death, when it starts to decay.

Another big radiocarbon-dating tool with roots in nuclear science is called "enrichment." It's a process of concentrating the element and is used because carbon 14 is a very tiny part of the overall carbon present in living things.

When the technique first was being developed, carbon 14 dates were tested against known-age materials such as Egyptian tomb relics.

Trees were another key to understanding the changing environment of the last several thousand years. By matching radiocarbon dates with tree rings, coral and other objects, many scientists now are fairly confident in radiocarbon's ability to take them back 30,000 years.

Radiocarbon dating isn't deemed useful beyond about 50,000 years because too little carbon 14 is left by then and because current chemistry can't weed out background contamination.

But there are other problems. For one thing, the creation of carbon 14 - which comes from nitrogen in the upper atmosphere - is not constant because the sun's nitrogen production fluctuates. And oceans, the other major reservoir of carbon dioxide, release different amounts of the gas depending on their temperature.

Those kinds of problems have fortified a group of creationists who discount carbon 14 dating almost entirely or give it only a few thousand years of accuracy. They essentially charge that scientists don't know the rate of carbon production and therefore the dating is unreliable.

Stafford, however, doesn't believe those questions invalidate carbon 14, especially since scientists are aware of some of the method's limits and account for them. He said it's like decreasing cooking time when using an oven that cooks at a hotter temperature than its gauge shows.

"Any kind of dating has some kind of difference from true reality," he said.

Stafford's goal is reduce the uncertainty. "There's all kinds of environmental contamination over geologic time," he said. "So you have to clean up the protein."

The first step in carbon dating is to remove calcium from bones by using acid - the equivalent of the old circus trick in which strongmen bent chicken bones after soaking them in vinegar to remove minerals.

Without calcium, the bones retain their shape but are a rubbery collection of protein called collagen.

Through numerous iterations of heating, cooling, freeze-drying, filtering, soaking and sterilizing, collagen is transformed over several days into a syrup, a gas and then graphite the size of a pencil tip. The material used in the testing is destroyed by the process.

The manipulations reduce impurities that throw off dates. Even then, tests of different proteins from the same bone can give different results.

That meant the bones were from two people - who lived 1,600 years apart.

Tests on individual amino acids by Stafford in 1998 confirmed the age difference between the skeletons.

With only one test, however, the Montana fragments would have appeared much younger than Stafford believes them to be. He's saving pieces to test in a decade when technology further advances the discipline.

"This experiment is strong support for ... why no single radiocarbon measurement is sufficient proof of a rare human skeleton's geologic age," he said.

That kind of uncertainty fueled Stafford's fears about Kennewick Man and the possibility government lawyers would select a date they wanted to support their case, quashing the scientific complexity and potential uncertainty.

Kennewick Man "is of such incredible complexity ... that one number is not going to do it," he said.

AMS, developed in Canada in the 1970s, was major step in dating remains because it can derive dates from tiny objects such as pollen grains, seeds and hair. "So many more kinds of archaeological and geological samples can be dated than ever before," said Higham, of the New Zealand laboratory.

For instance, AMS was used to authenticate the ancient Bible texts called the Dead Sea Scrolls. It also was used to determine the Shroud of Turin, the supposed burial cloth of Jesus, was roughly 700 years old.

Stafford often busies himself with much older remains, and he's achieved an international reputation for his quality work. A vacuum pump hums in his lab as he sits down to his computer, which holds two decades of charts, notes and numbers about ancient relics.

Each radiocarbon date costs roughly $800 - too much for scientists to use more than sparingly - and requires tedious attention to fill and filter test tubes.

"Nobody has that kind of money," said Stafford. "If I had to pay for them, I would be bankrupt."

The price tag reduces the number of dates archaeologists can afford to get to maybe just 10 percent of the number they should get for any given site, Stafford said. "What you need to do is massively increase the number of dates."

That's something he hopes to accomplish with his current project, the development of an automated system to replace tedious test tube work now done by hand.

By reducing the possibility of human error and increasing the amount of samples his two-person lab can process, Stafford appears close to offering archaeologists a new lower-cost option for radiocarbon dating and advancing science another step.