The biggest review ever done of what humans ate for two million years was published in 2021, and it has not made it onto a single plate graphic. Three researchers, two at Tel Aviv University and one in Portugal, went through about 400 studies and pulled out 25 separate lines of evidence, from our genes to our guts to the bones in the ground. The stomach says hunter, with an acid at a pH of 1.5, stronger than most predators' and close to a scavenger's, strong enough to kill the bacteria in meat that was eaten over days and weeks. The fat says hunter, stored in tens of billions of small cells the way a carnivore stores it, unlike the fewer, larger cells of a fruit-eating ape. The genome says hunter, with stretches of DNA shut down in humans to suit a fat-rich diet where the same stretches in the chimpanzee were opened up for sugar. The gut says hunter, with most of its length given to the small intestine that absorbs meat and fat, and a colon a fraction of the size of an ape's. The children say hunter, weaned at 2 to 3 years where a chimpanzee suckles for 5, because a mother with meat to hand can feed a toddler something other than milk. The tools say hunter, with spear points and butchering blades for nearly two million years, and the grinding stones for seeds turning up only near the very end. The rubbish says hunter, with camp sites full of elephant, hippo and mammoth bone, and the prey getting smaller over time as the giants were eaten out. The bones say hunter, with nitrogen readings in Neanderthals and early modern humans that sit above the wolf and the hyena, at the very top of the food chain. Put together, every line points the same way: from Homo erectus, about two million years ago, humans lived as hypercarnivores, and only turned to plants in numbers when the big animals ran out, in the last stretch before farming. Two million years on meat and fat, and about 12,000 on grain, which is under 1% of the time we have been human. The plate graphic puts the grain at the base and the meat at the tip, which is the whole history of the species printed upside down.

My most controversial nutritional opinions, in no particular order, so the replies can pick a fight efficiently. - Chicken tastes of nothing because it is nothing. - Salt is a farming invention and I haven't added it in years. - You do not need to eat liver. The animal was using it as a filter. - Vegetables are very healthy, once a cow has eaten them. - Fruit is bait with a stone in it. - Fibre is a word for the part you cannot digest, sold as the point. - Seed oils caused the diabetes. Sugar just turned up to help. - Carbs are not poison. They are a hobby. - Grass-fed is a label for the default. Every British cow is standing on the label. - 30% fat mince was the normal mince. The lean stuff is the deviation. - Butter lives on the counter. The fridge is for people who ration it. - Raw milk is the only food on earth designed to be food. - Olive oil is a seasoning the Mediterranean cooked in lard beside. - Mutton beats lamb. The lamb was two years short of flavour. - A bacon cheeseburger without the bun is as healthy as it gets. - Sunburn is a seed oil problem wearing a sun costume. - The only animal we cannot do without is the one that eats grass. Every one of those is checkable, which is the part the replies find hardest.

A Nobel Prize-winning chemist fed cows no protein at all for years, and they gave milk, and the milk was full of protein. Artturi Virtanen won his Nobel for chemistry in 1945. In the 1960s he took dairy cows off every protein in their diet and fed them urea and ammonium salts, which are nitrogen and nothing else, with cellulose and starch for energy. The cows made milk. Full milk, with every essential amino acid in it, for years, through several lactations. The microbes in the rumen took the nitrogen and built the protein from scratch, and the cow digested the microbes. They built every B vitamin as well, including B12, which no plant and no animal can make and which comes, in the end, from a microbe or nowhere. A cow is the only farm animal that manufactures protein. A pig and a chicken can only move protein from one place to another, and the place is usually a soy field. Feed a pig a kilo of soy protein and you get less than a kilo of pork. Feed a cow grass with no protein worth the name and you get a kilo of beef and milk anyway. Grazing cattle produce more protein a human can eat than they consume. A cow is a protein factory with a grass intake and a chemist-proof design, and she can run it on nitrogen and sunlight. Every plant-based plan to replace her begins with growing the protein first.

The scan that finds cancer works by injecting radioactive sugar, because a tumour takes up more of it than the tissue around it. Most cancer cells burn sugar the wasteful way, like yeast, so they need far more of it than healthy cells to keep growing. The tracer is a fake sugar the cell swallows and cannot finish, so it gets trapped inside and glows. On the screen, the cancer lights up from eating it. The day before the scan, the patient is put on a low-carb, no-sugar diet. If their blood sugar is still too high on the morning, the scan can be cancelled, because the sugar already in the blood would hide the tumour. The hospital knows exactly what the tumour wants, and keeps it off the menu for one day. Then Britain's biggest cancer support charity raises its money with coffee mornings full of cake. Channel 4 raises money for Stand Up To Cancer with a celebrity Bake Off. America's biggest breast cancer charity once sold pink buckets of fried chicken with KFC. The tea trolley on the chemo ward comes round with biscuits. Medicine finds the tumour with sugar, then holds a bake sale to fight it.

University debate: "Fruit and honey were the staples of the human evolutionary diet." Nutritionist: "We're primates. Primates eat fruit. Our colour vision evolved to spot it, our sweet tooth evolved to want it, and the Hadza in Tanzania still get a sixth of their calories from honey. Sugar is ancestral." Anthropologist: "What month is it in your ancestral forest?" Nutritionist: "Sorry?" Anthropologist: "Wild fruit comes in a window. A few weeks, then it's over. What's the fruit-eater doing in the other forty-five?" Nutritionist: "Finding other fruit." Anthropologist: "At latitude fifty, in January, forty thousand years ago, with the glacier a day's walk north. Name the orchard." Nutritionist: "Humans evolved in Africa." Anthropologist: "And left it. We've been in Europe and Siberia for forty-five thousand years, through an Ice Age, on nothing you'd recognise as a banana. The mammoth was the fruit." Nutritionist: "The Hadza prove honey is a staple." Anthropologist: "The Hadza climb thirty feet up a baobab, smoke out a hive, get stung half to death and come down with a comb full of grubs. They eat the grubs. Bee larvae are fat and protein. The honey is the wrapping, and it's a few weeks a year, on the equator." Nutritionist: "It's still sugar, and they thrive on it." Anthropologist: "So does a bear. He eats every berry on the mountain in September and sleeps till April. Fruit is how an animal gets fat on purpose before the food runs out. Our liver still does exactly that with fructose. You've taken a seasonal fattening switch and left it pressed down for twelve months." Nutritionist: "Our sweet tooth is proof we were built for it." Anthropologist: "Your sweet tooth is one receptor. You've got twenty-five for bitter, because most of what grows wants to poison you. A tongue built for fruit would be a tongue that could taste more than one of them." Nutritionist: "What about the apple? The grape?" Anthropologist: "The wild apple is a crab the size of a marble and tastes of battery. The wild banana is seeds held together by spite. Everything on your fruit bowl was bred in the last few thousand years to be a sweet nobody's ancestor ever met." Moderator: "Closing statements." Nutritionist: "Sugar from fruit is natural, ancient, and the body was designed to enjoy it." Anthropologist: "The body was designed to enjoy it for three weeks and then go hunting. You've skipped the hunting and kept the three weeks going since 1980." [The nutritionist had brought a banana. It stayed in the bag.]

A healthy cholesterol has been redefined six times in my parents' lifetime, and every single redefinition went the same direction. 1960s: anything under 300 is normal. Most of the country is fine. 1984: a government conference declares 200 the line. Overnight, half of American adults are abnormal. 1988: the target moves from total to LDL, and LDL under 160 is the goal. 2001: LDL under 130. Then under 100 is announced as optimal. Eleven million more Americans become patients in one afternoon. 2004: under 70 for the high-risk, and the panel that chose the number has eight members with drug company money out of nine. 2013: the targets are scrapped for a calculator, and the calculator qualifies most people over sixty on their birthday. 2019: Europe sets the goal below 55 for the very high risk, a number almost no unmedicated adult alive has ever recorded. 2026: the conversation has moved to a new particle, with a new test, and a new threshold to miss. Heart disease was the number one killer when normal was 300. It is the number one killer now. The line has fallen by two thirds. The deaths have not followed it anywhere. A target that only ever moves toward the drug is a sales figure with a lab coat on.

Seed oils were sold as paint for a century before they were sold as food, and they do in you what they do on a window frame. Linseed oil hardens on a fence post in a few days. Chemists call it a drying oil. Soybean oil hardens too. So does sunflower, so does safflower. They were sold to the paint trade before they were sold to the kitchen. Linoleum was invented in 1860 and it is named after linseed oil, because that is what it is, oxidised and pressed into a floor. The oil does not dry by evaporating. It dries by oxygen attacking the double bonds in its fats and welding them into a hard skin. The oil in your chip pan and the oil in your body carry the same double bonds, so the same attack runs there, with aldehydes thrown off as it goes. A painter calls that curing. A biochemist calls it lipid peroxidation. A doctor calls it inflammation and prescribes something for it. Once the oil is in your fat, it stays about two years, drying from the inside, every time it meets oxygen or sunlight. Butter never dried a fence post. Tallow never varnished a boat. Saturated fat has no double bond for oxygen to attack, which is why it sits in the pan for a week and why it sat in your great-grandmother's cells for a lifetime. A fat that sets hard in the air was never a candidate for the inside of an artery. The flooring industry understood the chemistry in 1860. The heart charity recommended it in April.

A cow cannot add a single atom of carbon to the sky, and the people who say she can have never followed one atom round. Grass is made out of air. The plant pulls carbon dioxide down and builds a leaf from it. The cow eats the leaf. The carbon is now in the cow. Some of it comes back out of her as methane. One carbon atom, four hydrogens, belched. Methane lasts about 12 years up there. Then it breaks back down into carbon dioxide. The grass pulls it down again. The cow eats the grass again. The same atom, round the same loop, since the first grazing animal walked onto the first grassland 50 million years ago. Nothing is added. The cow is a carbon atom's way of getting from one blade of grass to the next. A car works differently. The petrol was carbon that spent 300 million years locked under rock. Burn it and that carbon is in the sky, new, for a thousand years, and no cow on earth can bring it back down. A herd that stays the same size adds no warming at all. The methane going up equals the methane breaking down. Her grandmother's belch is already in this year's hay. The whole case against the cow rests on counting a loop as a leak. It is an error you can only make with the answer already decided.

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.