"When I saw her," Fisher says, "my first thought was, Oh my goodness, she's perfect—even her eyelashes are there! It looked like she'd just drifted off to sleep. Suddenly, what I'd been struggling to visualize for so long was lying right there for me to touch." Other than the missing hair and toenails, and the damage she'd sustained after her discovery, the only flaw in her pristine appearance was a curious dent in her face, just above the trunk. But her general appearance and the healthy hump of fat on the back of her neck suggested the baby had been in excellent condition at the time of her death. A deeper examination into her teeth, internal organs, stomach contents, and other features promised to reveal a wealth of new information on normal mammoth biology and lifeways.

Fisher was particularly excited about one specific part of Lyuba's anatomy: her milk tusks. Tusks are modified incisors that grow continuously in layers throughout an animal's life. Over 30 years of studying mammoth tusks, Fisher had figured out that these deposits were laid down in yearly, weekly, and even daily increments, and that, like the rings of a tree, they contained a detailed record of the animal's life history. Thick layers represented rich summer grazing, while thin ones indicated sparse winter fare. From a sudden narrowing of the strata around the 12th year, Fisher could discern when a young male became sexually mature and was driven away by its mother from the matriarchal herd; some years later came signs of the ferocious musth battles that adult males waged to determine who would win the opportunity to mate. Finally, in the layers at the root of the tusk that are the last to form, Fisher found clues to how an animal died—a slow dwindling caused by injury, illness, or environmental stress, or the sharp break of sudden death. He also found that the levels of certain chemical elements and isotopes in the tusks provided data on the animal's diet, climatic situation, even major changes in location such as migration.

Through his career Fisher has taken hundreds of tusk samples, and he believes they suggest an answer to the vexing question of the great extinction in the late Pleistocene. At least in the Great Lakes region of North America, where the bulk of his samples were unearthed, mammoth and mastodon tusks show that these animals continued to thrive, despite late Pleistocene climate change. On the other hand, to Fisher, the tusks often revealed telltale evidence of human hunting. His samples from late in the mammoth's reign frequently came from animals that had died in the autumn, when they should have been at their physical peak after summer grazing and less likely to die of natural causes—but also when human hunters would have been most eager to stockpile food for the coming winter. These tusks often came from males, who, like living elephants, probably lived alone and would have made easier targets for hunters than females traveling in matriarchal herds. Many remains were found in peat bogs and bodies of water, where according to Fisher early hunters may have submerged them to preserve the meat. The North American specimens also appeared to show a decline through time in the average age of maturation, which Fisher believes might also be caused by hunting pressure. He had done limited work in Siberia, but his measurements of tusks from Wrangel Island, off the coast of northeastern Siberia, where the last mammoths died out 3,900 years ago, suggest similar conclusions.

One problem with interpreting mammoth tusks, however, was that they almost never came with mammoths attached, making it hard for Fisher to test his inferences about health and age. Lyuba's superb state of preservation promised to change that. By giving direct evidence of her diet and state of health, her stomach and intestinal contents and the amount of fat on her body could provide an independent corroboration of the brief dietary "journal" recorded in her still unerupted milk tusks. "In this case we don't need a time machine to see how accurate our work is," Fisher says. Moreover, since the milk tusks grow from early in gestation to around the time of birth, Lyuba could shed new light on a critical period in a mammoth's life: the time in the womb (estimated to be 22 months, based on an elephant's gestation length), followed by birth. A traumatic event for any mam­mal, the moment of birth is recorded in tooth microstructure by a distinct neonatal line. By comparing her milk tusk development with that of elephants, the scientists initially estimated her age at death to be four months. Counting the increments of ivory laid down after the neonatal line would provide a much more accurate age.