Night falls. The herd moves on, but the mother lingers. Yellow moonlight throws her humpbacked shadow across the glistening mud. The moon sets, and stars glow in the chill heavens. Just before dawn, she takes a last look at the spot where the earth swallowed her baby, then turns and follows the herd north, toward summer pastures.

On a May morning in 2007, on the Yamal Peninsula in northwestern Siberia, a Nenets reindeer herder named Yuri Khudi stood with three of his sons on a sandbar on the Yuribey River, holding council over a diminutive corpse. Though they'd never seen such an animal before, they knew it well from stories their people sang on dark winter nights in their storytelling lodges. This was a baby mamont, the beast the Nenets say wanders the frozen blackness of the underworld, herded by infernal gods just as the Nenets herd their reindeer across the tundra. Khudi had seen many mammoth tusks, the honey-colored, corkscrew shafts as thick as tree limbs that his people found each summer. But he had never seen an entire animal, let alone one so eerily well preserved. Apart from its missing hair and toenails, it was perfectly intact.

Khudi was uneasy. He sensed this was an important discovery, one that others should know about. But he refused to touch the animal, because the Nenets believe that mammoths are dangerous omens. Some Nenets even say that people who find a mammoth are marked for early death. Khudi vowed to placate the infernal powers with the sacrifice of a baby reindeer and a libation of vodka. But first he traveled 150 miles south to the small town of Yar Sale to consult with an old friend named Kirill Serotetto, who was better acquainted with the ways of the outside world. Serotetto listened to his friend's story, then bustled him off to meet with the director of the local museum, who persuaded the local authorities to fly Khudi and Serotetto back to the Yuribey River in a helicopter.

When they arrived on the sandbar, however, the mammoth had vanished.

Mammoths are an extinct group of elephants of the genus Mammuthus, whose ancestors migrated out of Africa about 3.5 million years ago and spread across Eurasia, adapting to a range of woodland, savanna, and steppe environments. The best known of these proboscideans is the woolly mammoth, Mammuthus primigenius, a close cousin of living elephants and about the same size. It first appeared in the middle Pleistocene more than 400,000 years ago, probably in northeastern Siberia. The woolly mammoth was highly adapted to cold, with a dense undercoat, guard hairs up to three feet long, and small, fur-lined ears. Immense curving tusks, used primarily for fighting, may have also been handy for foraging beneath the snow. Because mammoths often died and were buried in sediment that has been frozen ever since, many of their remains have survived into modern times, particularly in the vast deep freeze of Siberian permafrost.