At 180 degrees, beef dripping sits in the pan and waits. At 180 degrees, sunflower oil has started to come apart. After 20 minutes, the dripping is unchanged. The sunflower oil is giving off aldehydes at 20 times the daily limit the World Health Organisation allows. After an hour, the dripping is unchanged. The sunflower oil is a soup of the compounds a laboratory buys to damage a cell on purpose. After a week, which is how long a takeaway fryer runs, the dripping has thickened. The sunflower oil has set into a brown varnish you need a chisel to shift. That varnish is paint drying. Sunflower, soybean and linseed oil react with air and go hard, which is why decorators use them and why your roasting tin is sticky. Saturated fat has nothing for the oxygen to grab. That is the whole of the chemistry, and it is why a tin of dripping keeps under the sink for a year. The chippy frying in dripping has a queue out the door. The chippy frying in vegetable oil has a sign saying it is the healthy option. One of those fats was in the fryer when Britain had almost no heart disease. The other went in around 1960. The cardiology ward opened shortly after.

People ask me why I'm so obsessed with ruminants. I've given it some thought, and my conclusion is that I'm not obsessed enough. A cow walks onto a wet hillside that grows nothing a human can eat, puts her head down, and comes back with steak, butter, cream and a pair of boots. She does it with a 150 litre fermentation tank she carries inside her, stocked with more bacteria than there have ever been people, which she feeds, waters and keeps at blood heat herself. Grass goes in. The bacteria take apart the one thing no animal can digest, and she lives on what they make. Then she digests the bacteria as well. Nothing is wasted. Even the fat comes out the far side rebuilt into something stable enough to fry in. Fuel: rain and sunlight. Emissions: next year's grass. She repairs herself, builds her own replacement every spring, and improves the ground she is standing on while she works. The finest engineers alive have spent billions trying to copy one chamber of her stomach in a steel shed, and so far they have made a paste. We have leaned on that machine for everything. The word capital comes from cattle, because a herd was the first bank. Domesday Book is written on sheep, and so was every deed in England for 500 years. Ruminants clothed our armies, lit our houses and carried our laws. Civilisation is a thing that happened to people who kept them. And they are such good company about it. A sheep remembers fifty faces for two years, which is forty-six more than I manage. A cow has a best friend, and her heart rate drops when that friend is beside her. A goat that cannot solve a problem will turn and look to you for help, as a dog does, and then ignore your advice. Let a herd out onto spring grass after a winter indoors and half a tonne of animal will skip. They ask for grass, rain, and to be left to get on with it. After ten thousand years of feeding, dressing and housing us, they will still walk over to the gate to see who you are. So no, I will not be calming down.

Settled science has a pattern, and it is the same man every time: a committee with the funding, and one awkward person they laughed at. It was settled that stomach ulcers came from stress. In 1984 an Australian registrar drank a flask of the bacteria, gave himself gastritis, and took the Nobel Prize in 2005. It was settled that the continents did not move. The weatherman who said they did was mocked for 20 years, froze to death on the Greenland ice in 1930, and was proved right in the 1960s. It was settled that cutting the front off a brain cured madness. It won the Nobel Prize in 1949. Forty thousand Americans were lobotomised before anyone was allowed to say it did not. It was settled that a heart attack meant six weeks flat on your back. Two Boston cardiologists sat their patients in an armchair in 1952, the clots stopped, and the deaths halved. It was settled that a gentleman's hands could not carry disease. The Hungarian doctor who made his students wash them cut deaths on his ward from 18% to 2%, was driven out, and died in an asylum. It was settled that cigarettes were fine. More doctors smoked Camels than any other brand, said the advert in 1949. Two British epidemiologists published the lung cancer numbers the next year and were ignored for a decade. It was settled that margarine was better than butter. The Illinois chemist who found the trans fats in it in 1957 was dismissed for 50 years, watched them banned in 2015, and died at 102. It was settled that eggs raised your cholesterol. Forty years of advice was removed from the guidelines in 2015 without a word of apology. It was settled that babies sleep on their fronts. The advice ran from 1956 to 1991, and the researchers who finally counted estimated 60,000 cot deaths that need not have happened. Nine settled positions. Each one held by the people with the committees, the journals and the word science. Each one broken by one person with the evidence and a bad reputation. Settled is the word a committee uses for the moment it would prefer you stopped checking.

The strongest man in the world in 1983 was a Lincolnshire policeman who ate a dozen eggs, 6 lb of red meat and 7 pints of milk a day. Geoff Capes was the seventh of nine children in Holbeach, a land worker's son. He left school at 14 and hauled potato sacks for a living. In 1970 he joined the Cambridgeshire police on £9.50 a week, and trained around the shifts. By 1980 he was 6 ft 5 and 23 stone and could run 200 metres in 23.7 seconds. That May at Cwmbran he put the shot 21.68 metres, a British record that stood for 23 years. Two Commonwealth golds. Seventeen British titles. Then he gave up the police to go to the Moscow Olympics against the government's wishes, and went into strongman. World's Strongest Man in 1983 and 1985. Six times world champion at the Highland Games. On television he tore phone directories in half, flipped a car three times in under 20 seconds and pulled a 7.5 tonne lorry 30 metres. He said he was burning 10,000 calories every four or five hours. A local butcher sponsored him in steak. Then eggs, bread, pilchards, and the milk. The gentle side went into budgerigars. He bred 300 of them, became world champion at that too in 1995, and was president of the Budgerigar Society. He died in October 2024 at 75. Every gym in Britain now has a man in it drinking a shake made from whey, which is the thing left over when you take Capes's dinner out of the milk.

Hector put his head on the ground on Sunday so that a donkey could groom his neck, and he has done it every afternoon since. Horses scratch each other. Two that are bonded stand nose to tail and work their teeth along the other's withers, the ridge at the base of the neck where a horse cannot reach himself, and it is not a small thing. A horse being groomed there drops his heart rate the way a man does when somebody he trusts puts a hand on his shoulder. It is how a herd says the thing it has no other way of saying. Hector had nobody to do it with for seventeen years. A horse on State and Ceremonial is groomed by a man with a brush, which is clean and thorough and nothing whatsoever like being groomed. So in Denbighshire he turned, one afternoon, and offered his withers to the only other animal in the field, the way a horse does, and the donkey's teeth landed on the middle of his back, because Nelson's head comes up to about the horse's chest and no amount of goodwill will change that. Nelson chewed at a patch of flank for a while, politely, and then went back to his hay. Hector stood there with his neck itching. On Sunday the farmer looked out at about three and the horse was lying down. Not asleep. Down on his chest in the grass with his legs folded under him, the way he has only lately learned to do, with his head stretched out along the ground, and the donkey was standing over him with his teeth in the horse's mane, working along the top of the neck from the ears to the withers, slowly, with great concentration, like a man trimming a hedge. Hector's eye was half shut. His lip was hanging. Seventeen hands of Cavalry Black lay in a Welsh field like a dropped coat and was groomed by an animal a third his size, and the donkey, who has never asked anybody for anything, moved a few inches along and carried on. Then Nelson stopped and turned, and stood, and presented his own withers, which are at about the height of a kitchen table. The horse lifted his head off the ground, took the donkey's mane in his teeth, and groomed it without getting up. They were at it for twenty minutes. The farmer's wife came out to see what he was looking at and the two of them stood at the window and did not speak, because there was nothing to add, and because in thirty years of horses neither of them had seen one go to the ground to be scratched. He lies down now at about three every day. The donkey walks over. The farmer has stopped looking out at three, because he says it feels like reading somebody's letters.

The most feared soldiers in medieval Europe were dairy farmers. Their enemies had a name for them, and it was meant as an insult. They called them the cow-Swiss. The cantons of the high Alps had almost no land that would grow grain. What they had was summer pasture. From the 1300s the people there turned over almost entirely to cattle. They lived on milk, butter, cheese and meat, drove their surplus animals over the passes to sell in Italy, and bought in what little bread they wanted. Their overlords were the Habsburgs. In 1315 a duke rode in with an army of armoured knights to bring them to heel. About 1,500 herdsmen caught the column in a narrow pass beside a lake and destroyed it. At Sempach in 1386 they did it again, on open ground, and killed the duke. In the 1470s they wiped out three armies of the richest prince in Europe, one after another, and left him dead in a frozen ditch. Contemporaries could not get over the size and stamina of these men. Every king in Europe wanted to hire them. In 1506 the Pope chose them as his bodyguard, and they are still at the gates of the Vatican in the same uniform. The Germans to the north mocked them as cowherds and milkers, and made cruder jokes than that. The Swiss went to war over the insult in 1499 and won that as well. Machiavelli, who had seen them fight, put it in a single phrase. The Swiss, he wrote, are the most armed and the most free. They had no king, no nobles and no wheat. Europe laughed at them for living on cows, and for 200 years could not beat them.

In the 1990s Canadian scientists put the traditional Inuit caribou-skin suit into a cold laboratory alongside the best modern expedition clothing and army Arctic gear. The caribou won. The design is thousands of years old. Two layers. The inner one is worn with the fur against the skin. The outer one has the fur facing out. Between them is a pocket of still air. The whole outfit weighs about the same as a modern down suit. The secret is in the hair. Each caribou hair is hollow, a tiny sealed tube of air, and there are thousands to the square inch. It is the best natural insulation known. Frost does not stick to it. A hunter can sit motionless over a seal hole for hours at 40 below. The polar explorers who lived learned this from the people who already knew. The ones who trusted what was sold in London shops had a harder time. And the suit was only half of it. The people inside it ate seal, caribou, fish and whale, and very little else. They burned fat for warmth from the inside and wore fur for warmth on the outside. For 4,000 years they lived, raised children and grew old in a place where nothing green grows for nine months. No plant fed them and no plant clothed them. Every single thing that kept a human being alive in the Arctic came off an animal. We now make jackets out of spun oil, fill them with plastic wadding, and sell them with a picture of the Arctic on the label. The test was run in a freezer by people with instruments. The reindeer came first, as it had every winter for forty centuries.

Your body keeps two months of fat in storage and less than one day of carbohydrate, which tells you what it was expecting to run on. Your entire bloodstream holds about one teaspoon of sugar. Any more and an alarm goes off. Your liver and muscles hold perhaps 2,000 calories of carbohydrate. A day, if you sit still. A lean adult carries around 100,000 calories of fat. Six weeks and more, with no further instructions. You store vitamin B12 for three to five years. You store vitamin A for months, in the liver, like every other hunter. You store vitamin D in your own fat, to see you through a winter. You store almost no vitamin C. Scurvy takes about a month. Look at what gets a warehouse. Fat, and the nutrients that come in an animal. Those arrive in gluts. A kill, a feast, then nothing for a week. So the body built somewhere to keep them. Carbohydrate gets a shelf. If none turns up, the liver simply makes its own, and has done every night of your life. There are essential fats. There are essential proteins. The textbook requirement for carbohydrate is zero, and it says so. No engineer builds a 100,000 calorie tank for the reserve fuel and a one day tank for the main one. The plate they drew for you is two thirds the fuel you were never built to store.

University debate. The motion: "There is no such thing as a safe tan." Dermatologist: "Ultraviolet light is a proven carcinogen. Every tan is damage. The only responsible advice is shade, clothing and factor 50, all year round." Anthropologist: "When did humans lose their fur?" Dermatologist: "I'm not sure that's relevant." Anthropologist: "At least 1.2 million years ago. In equatorial Africa. Naked, outdoors, all day, under the strongest sun on the planet. How did the species cope without a pharmacy?" Dermatologist: "Dark skin. Melanin." Anthropologist: "A built-in defence, then. And when people walked north into weak sunlight, what happened to it?" Dermatologist: "The skin got paler." Anthropologist: "Why?" Dermatologist: "...To let more ultraviolet in. For vitamin D." Anthropologist: "Most of that in the last 8,000 years. Evolution stripped the pigment out of an entire continent because the people who got more sun on their skin left more children. You've stood up tonight and called that a design fault." Dermatologist: "They didn't live long enough to get skin cancer." Anthropologist: "Who gets more melanoma today? The roofer or the accountant?" Dermatologist: "It's complicated." Anthropologist: "It's the accountant. The people outdoors all year get less of it than the people who see the sun for a fortnight in Spain. And melanoma in Britain has more than doubled since the early nineties, across the best-creamed decades in human history." Dermatologist: "That's better diagnosis." Anthropologist: "It's a remarkable defence of a product. The more we use, the more cancer we find, and the answer is a higher factor." Moderator: "We're out of time. It's a lovely evening, there's a terrace." [The dermatologist is already putting on a hat.]