Interlude with the Ice Man

When Anne Stone left for Germany, she had no idea she'd get to see the Ice Man's tattoos.

Stone, a graduate student in anthropology at Penn State, is a fledgling expert in a fledgling discipline: the study of ancient DNA. At a meeting in Europe in 1991, she met some of the field's leaders, including biologist Svante Pääbo, professor at the Institute of Zoology at the University of Munich. The following year she received a Fulbright grant, and left for a year in Pääbo's lab.

She went bearing samples from her own research, on a set of bones unearthed from a prehistoric cemetery, the remnant of a settlement of the Oneota people in the Central Illinois River Valley. In Pääbo's lab, she intended to see what his genetic techniques could teach her about ancient Oneota society.

Then the Ice Man came.

The mummified body of a 5,000-year-old man had been discovered in a glacier in the Tyrolean Alps in 1991, and had quickly become a media superstar: a nearly intact specimen of Stone Age man, complete with fur clothing and a copper axe.

Some people thought the Ice Man was a hoax. There was speculation that the mummy had been brought from somewhere else—maybe South America—and planted in the Alps by a prankster. The Ice Man's keepers at the University of Innsbruck asked Pääbo to look into the matter. DNA sequence data, if it could be obtained, should yield information about the true origin of their prize.

When Pääbo went to Innsbruck, Stone went along for the ride. The team was allowed to remove a tiny sample of bone and tissue, a total of about a gram, from the Ice Man's hip, which had been damaged during initial efforts to pry the body from the glacier. While Pääbo and Oliva Handt, the biologist who would do most of the sequencing, took their sample, Stone was "kind of standing in the doorway," she says.

"He has tattoos," she reports, of the Ice Man's appearance. "On his ankles and his lower back."

The first analysis on the precious sample was not promising. "When Oliva started doing the sequencing," Stone remembers, "she got lots of different sequences," a confusion akin to picking up dozens of fingerprints at the scene of a crime. "They were probably the sequences of the people who had handled him getting him out."

To remove this modern contamination, Handt cut away the outside layer of the tissue sample, and assayed only the core.

Once this was done, Stone says, things went better. "She only got one sequence." As a further test, Handt checked her results against those obtained by a group at Oxford University in England. Using another sample from the mummy's hip, the Oxford group came up with the identical sequence. "So we're pretty sure it's the real thing," Stone says: the Ice Man's DNA.

The recovered sequences were of mitochondrial DNA, genetic information found outside the cell nucleus in the organelles that produce a cell's energy. Mitochondrial DNA, Stone explains, is more likely than nuclear DNA to survive the ravages of time, simply because it is so much more plentiful. "There are hundreds of copies in each cell," she says, as opposed to a single copy of nuclear DNA.

To make their identification, Pääbo's group focused on a particular stretch of mtDNA that is known to vary, or mutate, along with human populations. "You can use these mutations to follow a population's history," Stone explains.

Their findings, as reported in the journal Science, are that Ice Man's DNA is indeed consistent with a European lineage—specifically, it is similar to that of people living in northern Europe today. "It removes all the suspicions that the body was a fraud—that a body was placed in the ice," Pääbo told Science.

Stone herself worked on trying to coax some nuclear DNA from the sample. In her Oneota research, she had developed a way to determine the sex of a skeleton using nuclear-DNA markers, and she hoped to test her method on a known male specimen. Her efforts didn't pan out—the Ice Man's nuclear DNA was too far gone to yield anything usable.

Now, while Pääbo and his group continue to work on the Ice Man project, hoping to learn more from better DNA samples, Stone is back at Penn State, finishing her dissertation on that Illinois cemetery. She has no regrets.

"Ice Man is a very exciting, one-of-a-kind find," she says, "but also a sample of one. There's a limit to the kinds of questions he can answer."

She muses a moment. "It was a fun aside."

Anne Stone is a Ph.D. student in anthropology. (See an earlier report on her work in R/PS, vol. 13 no. 4, Dec. 1992, p. 10.) Her advisers are George R. Milner, Ph.D., associate professor of anthropology, 321 Carpenter Building, University Park, PA 16802; 814-865-1268; and Mark Stoneking, Ph.D., associate professor of anthropology, 512 Carpenter Building, 863-1078. Svante Pääbo, of the Institute of Zoology at the University of Munich, is a member of Stone's graduate committee.

The paper by Pääbo's group on the Tyrolean "Ice Man," which lists Stone as a co-author, appeared in Science, vol.264, p.1775, 17 June 1994.

Last Updated March 01, 1995