We entertain the illusion that we have chosen our lives. Why, if this is the case, do our apparent choices differ so little from those of other people? Why do we live and work and travel and eat and dress and entertain ourselves in almost identical fashion? It’s no wonder, when we possess and use it so little, that we make a fetish out of freedom.

Perhaps we have forgotten the bitter complaint made by Benjamin Franklin in 1753: “When an Indian Child has been brought up among us, taught our language and habituated to our Customs, yet if he goes to see his relations and make one Indian Ramble with them, there is no perswading him ever to return.” But when European Americans “have been taken prisoners young by the Indians, and lived a while among them, tho’ ransomed by their Friends, and treated with all imaginable tenderness to prevail with them to stay among the English, yet in a Short time they become disgusted with our manner of life ... and take the first good Opportunity of escaping again into the Woods, from whence there is no reclaiming them.” In 1785 Hector de Crèvecoeur asked two European refuseniks why they wouldn’t come home. “The reasons they gave me would greatly surprise you: the most perfect freedom, the ease of living, the absence of those cares and corroding solicitudes which so often prevail with us.”

We arose in a thrilling, terrible world. The African savannas on which the first hominids evolved were dominated by saber-toothed and false saber-toothed cats, giant hyenas and bear dogs. When human beings arrived in the Americas, 14,000 years ago, they found ground sloths the weight of elephants; a beaver eight feet from nose to tail; armadillos like small cars; giant lions and sabertooths; short-faced bears whose shocking armory of teeth and claws suggests they drove giant lions and saber-tooths off their prey. A bird in Argentina had a wingspan of 26 feet. Fanged salmon nine feet long migrated inland from the Pacific coast.

We carry with us the psychological equipment, rich in instinct and emotion, required to navigate that world. But our survival in the modern economy requires the use of few of the mental and physical capacities we possess. Sometimes it feels like a small and shuffling life. Our humdrum, humiliating lives leave us, I believe, ecologically bored.

At times this sensation has overwhelmed me. It happened in a newly discovered bone cave in southern England. The walls and floor were encrusted with calcite crystals that glittered in the torchlight. One of the archaeologists with whom I was exploring it handed me the atlas vertebra of a Bronze Age cow. Then he picked up another bone, this time with both hands: another atlas vertebra, but monstrous. “It’s the same species as the first one. But this is the wild version. The aurochs.” As I turned it over in my hands, feeling its great weight, I experienced what seemed like an electric jolt of recognition. It felt raw, feral, pungent, thrilling. The color seemed to drain from modern life.