Hairy clues to the Iceman's diet.

The neolithic man discovered in an Italian glacier in 1991 carried a bow and a quiver of arrows, leading archaeologists to label him a hunter. Chemical analysis of his hair now indicates that the Iceman was a strict vegetarian, at least just before his death.

"Hair is a really powerful tool as a record for human diet, and it is apparently intensely well-preserved," says Stephen Macko of the University of Virginia in Charlottesville. "The hair that's 5,000 years old [on the Iceman] was identical to the hair on my own head," showing no chemical deterioration, he says.

Macko measured the ratios of forms of carbon and nitrogen atoms preserved within the Iceman's hair. Both carbon and nitrogen come in light and heavy forms, or isotopes. Plants contain relatively little of the heavy isotopes, so the hair of herbivores has lighter isotopic ratios than does the hair of carnivores.

Researchers have previously studied ancient diets by analyzing the isotopic ratios in the bones and teeth of mammoths and other extinct species. This technique, however, requires large samples, and the molecules can degrade quickly, says Macko. With only a few millimeters of the Iceman's coarse hair, however, he found very low isotopic ratios, indicating no meat consumption as these strands were growing.

Macko has also studied other ancient hair samples. The isotopic ratios found in eight Egyptian mummies suggest that they had a relatively restricted carnivorous diet, whereas Egyptian Coptics had a much more varied one. "They [Coptics] had a huge variation in foodstuffs, equivalent to the modern grocery-store population," he says.