An Ancient Woolly Mammoth Left a Diary in Her Tusk

Scientists have written the biography of a 14,000-year-old female woolly mammoth by analyzing the chemicals in her tusk.

The animal, nicknamed Elma, was born in what is now the Yukon and stayed close to her birthplace a decade before moving hundreds of miles west into central Alaska, the study found. There she remained until she reached about 20, when she was most likely taken down by hunters.

Scientists are beginning to tell such ancient stories by looking at the layers of minerals that once accumulated each day on the outside of the tusks of mammoths and mastodons. As researchers study more tusks, they hope to settle some of the biggest questions about how the hulking mammals thrived for hundreds of thousands of years. They are also gathering clues to how mammoths and mastodons became extinct at the end of the Ice Age — perhaps with some help from humans.

“There are answers out there,” said Joshua Miller, a University of Cincinnati paleoecologist who was not involved in the new study but who has cut open a mastodon tusk in Indiana. He said it would be necessary to look at many tusks that spanned thousands of years.

“We’re just starting to build it,” Dr. Miller said, “and that’s exciting.”

Woolly mammoths grew their tusks much like living elephants do. Each day, a thin, cone-shaped layer of minerals built up on the tip.

“I like to describe it as ice cream cones stacked on top of each other,” said Matthew Wooller, director of the stable isotope facility at the University of Alaska Fairbanks.

Much like tree rings, the cones remained fairly distinct even after the animal died. Researchers started analyzing this chemical record in the 1980s, gaining clues about how baby mammoths weaned from their mothers and how their diet changed with the seasons.

More recently, Dr. Wooller and his colleagues figured out how to use mammoth tusks to track where the animals lived over the course of their life. They did so by measuring strontium, an element found in trace amounts in the plants the animals ate. If a mammoth spent a day grazing somewhere with a lot of strontium in the soil, the cone of minerals it grew that day would have a high level of strontium.