Once warm and full of trees and animals, Antarctica grew cold, and its creatures left or died, except emperor penguins. In a desert of ice, bound by an ocean, the stately penguins grow plump and sleek on summer fish, then by the thousands, in a line stretching for miles, march single file to their inland breeding ground. Even penguins going for the first time know the way. Once there, they carefully pick mates.

Their commitment is profound. The female delivers a single egg, which the male tucks on top of his feet, in a fold in his belly; then he stands still for two months in total darkness, freezing cold, and howling wind, without food or water, and only the huddle of other fathers to warm him. The mothers go back to sea, now even farther, for forage to take back in the spring. When they next see the massed males, each finds her mate without error, and knows the cries of a chick she's never seen.

The astonishing documentary of their yearly ritual, by French director Jacquet and cinematographers Laurent Chalet and Jerome Maison, was shot on the coldest, driest, darkest continent. In otherworldly beauty, only snow, ice, and penguins are seen. Even the penguins' predators, leopard seals, ignore them in the long winter.

Evolution created the penguins' habits. The ice shelf melts inward in spring, so the birds must go far inland, where the ice stays thick enough to hold them, if they and their offspring are to survive. Penguins who stop too soon during the in-bound trek risk losing eggs to the sea; penguins who walk farther raise more offspring. Eventually, every penguin descends from birds who walk farther in. But their lives are so strange that early Antarctic explorers, who saw them, had no idea where they came from, where they went, or if they were birds.

Apsley Cherry-Garrard's remarkable book, The Worst Journey in the World (1922), tells how he and two other members of Scott's 1910-12 South Pole expedition went to the mating grounds and returned with an egg. Cherry-Garrard retired to England, where he died in 1959. His friends said the trek, and later finding the frozen bodies of Scott and two other men, depressed him for life.

For Jacquet, who had transportation, warmth, food, and outside communication, the experience was easier. Still, it wasn't easy to make this documentary of penguins surviving by heroic determination. We watch in empathy.