Jane Orient, MD

How long an animal can go without food tells you what it was built to eat, and you can go weeks. A rabbit that stops eating for a day is a vet emergency. Its gut stalls and its liver starts to fail. A pony off its food for a few days can flood its own blood with fat and die of it. A cow needs grass going in around the clock to keep the microbes in her rumen alive. A lion eats up to 40 kilos at a sitting, then nothing for days. A wolf can bolt a fifth of its body weight in one meal, then go a fortnight without. A crocodile can go a year between meals. A pregnant polar bear digs into the snow and goes up to eight months without eating, giving birth and suckling her cubs on the way. An emperor penguin father stands through the Antarctic winter with an egg on his feet and eats nothing for about four months. A human stomach stretches from about a litre to four. A lean human can go about two months without food, living off fat that every other primate barely carries. Hunters in every culture ate until they couldn't move after a kill, and went without until the next one. The body was built to feast and fast like a predator. The diet sheet feeds it like a rabbit, a little every few hours, in case it panics.

The year is 8500 BC. You are an aurochs, six feet at the shoulder, and very little alive frightens you. Some people on the upper Euphrates have built a pen. About 80 of your mothers and sisters walk into it, and every cow that will ever live walks out. The bargain is simple. They keep the wolves off. You let them near the calf. It seems, on the day, like a fair exchange, and you keep your side of it for ten thousand years. The year is 4000 BC. There is a beam across your neck and a pointed stick dragging behind. You lean into it because the man beside you is leaning too, and he talks to you the whole length of the furrow. He has given you a name. When you die his children will cry, and he will not eat that week. Every field on earth for the next six thousand years is opened this way, by the two of you. The year is 2500 BC. In a temple in Sumer they carve you into the wall in white limestone: the priests milking you, the churn rocking, the butter poured into jars. You are washed every morning and counted every night. You are the most valuable thing the city owns and you are treated like it. Nobody carves the barley. The year is 1200. You haul stone up the hill at Laon, a load at a time, for a cathedral you will never be let inside. When the towers are finished the masons carve sixteen of you, life-size, and set you at the very top, looking out over France. The bishop gets a slab in the floor. Somebody remembered who did the lifting. The year is 1750. You come down off the Alp in September with flowers woven round your horns and a bell the size of a bucket, and the whole village is standing in the street in its best clothes to watch you pass. The finest milker walks at the front. She knows it. The year is 1852. You are one of six in front of a wagon in Missouri, with a family's whole life behind you and two thousand miles ahead. The children ride on the tailboard, and by Nebraska the youngest has named all of you. When the grass fails you are fed last and you pull anyway. A country is walked into existence at two miles an hour, which is your pace. The year is 1922. In Toronto a boy of 14 is dying of diabetes. He weighs 65 pounds and has days left. They inject him with an extract of your pancreas and he gets up and goes home. For the next sixty years every diabetic alive is alive because of you. Not one of them ever learns which of you it was. The year is 1946. Britain has just weighed and measured its children for a war and seen what the ones without you looked like. A bottle of your milk goes on every school desk in the country, by Act of Parliament. That is where you stand in 1946. You are named, garlanded, carved on cathedrals and written into law. Hold that thought. The year is 2006. A report comes out of Rome with your shadow on the cover. It says that you, stood in a field, are doing more harm to the sky than every car, lorry, ship and aeroplane on earth. The sum counted everything about you from the fertiliser to the fridge, and only the exhaust pipe of the car. The authors admit as much. By then the sentence is on a billion screens. The year is 2019. Thirty-seven experts publish the diet that will save the planet. Your share is a quarter of an ounce a day, one small burger a fortnight. A child comes home from school and asks her grandfather, who has got up at five to milk you for fifty years, why he is hurting the world. The year is 2023. The Dutch government is paying farmers to be rid of you for good, on condition they never keep you again. A paper on a minister's desk in Dublin costs out the removal of 200,000 of you from Ireland, the island that counted its kings' wealth in your heads. The year is 2026. Denmark has passed a law to tax your breath. There is a powder in your feed to stop you belching. A carton of oat water in the fridge says it is like your milk but made for humans. In a steel tank in California they are growing the thing that is meant to finish you off, and they feed it on corn. You ploughed every field they ever sowed. You hauled their cathedrals and carried their children across a continent. You fed their orphans and kept their diabetics breathing. In return you asked for grass and somebody to watch for wolves. You are still giving all of it. This morning, in the rain, on ground no plough could use, you gave it to people who have been taught to be ashamed of taking it. You know none of this. You know the gate, the voice, and the hand on your flank at five in the morning. He has read the report. He came anyway.

A wild donkey in the Arizona desert will dig a well six feet deep with its front hooves, and for half a century the United States government has been shooting it as a threat to the desert. August on a dry wash in the Sonoran. The creek has been gone since May. The sand is hot enough to cook on and every animal for miles is standing in what shade it can find, waiting for a rain that is not coming. A burro walks down the wash, stops at a bend for no reason anyone else can see, puts its head down and smells. Then it starts digging. Front feet, one after the other, like a dog after a bone, until it is in up to its shoulders and the bottom of the hole goes dark and wet. It drinks and walks off. Within the hour there is a queue. Mule deer. Javelina. A bobcat. A scrub jay standing on the rim. In 2021 a biologist called Erick Lundgren published the count in Science: 59 species of vertebrate drinking at donkey wells, 64% more species than at the dry stretches of the same streams, and in the driest months the donkeys were raising the amount of open water in the desert by 300% on average and by up to 1,450%. When the wells were abandoned, cottonwood and willow seedlings came up in them. The donkey had been planting the riverbank. Asked about his methodology, the donkey had another drink and left. When a beaver builds a pond, a film crew is sent. When a donkey digs a well, the Park Service sends a marksman. The burros came up from Mexico with the Spanish and the prospectors, carried the ore out of every mine in the West, and were turned loose when the mines closed. Then they were reclassified. In 1979 the National Park Service planned to shoot all 577 in the Grand Canyon. A writer called Cleveland Amory raised more than $500,000 and lifted 582 of them out by helicopter, slung underneath, the most expensive taxi ride a donkey has ever taken. Death Valley shot 400 between 1987 and 1994. Lundgren said that when he started, people did not think a donkey digging a hole was worthy of scientific attention. The animal was listed as a threat to the desert's water. It was the one bringing the water up. Fifty-nine species knew. The ones with the rifles had never sat by the hole.