In 1991 eight people were sealed inside three acres of glass in the Arizona desert to prove that a carefully designed farm could feed humans without the outside world, and the design had almost no room in it for animals. Two years later the only thing inside that had reliably fed them was a handful of goats. Biosphere 2 cost a hundred and fifty million dollars. A rainforest, an ocean, a savannah and a farm under one roof, with the door welded shut for two years and nothing allowed in or out. The farm was the heart of it, and the farm was built on the modern idea: crops first, grown intensively, with livestock as an afterthought at the edges. A few African pygmy goats for milk, a flock of chickens, and four small feral pigs chosen because they could live on scraps. The pigs did not last the year. In a sealed box short of calories a pig is a competitor, and the crew killed and ate them. The chickens barely laid, because the glass cut the light and there was nothing to feed them that would make an egg. That left the goats, and for two years the goats were the only source of fat in a world designed around vegetables. The accounts the crew wrote afterwards return to them again and again. The half glass of milk a day was the thing people lived for. When a kid was born it was eaten and the meal was written up like a feast. The men lost nearly a fifth of their body weight, the women a tenth, and the food they dreamed of was never the sweet potatoes they had in abundance. It was the animal they had been given too few of. The plants were also taking the air. To make the crops grow the soil had been enriched with compost, and the microbes in that soil breathed oxygen faster than anyone had calculated. The level fell from twenty-one per cent to fourteen, the air of a high mountain, until the crew could not climb a staircase without resting and oxygen had to be trucked in from outside. The design that put plants first had removed the thing everyone needed most. Nobody has ever run the experiment the other way, with a herd at the centre and the crops at the edge. It would not have needed a doctor to explain the results. They were given three acres and told to feed themselves on plants. They ate the pigs, worshipped the goats, and suffocated.

The heart attack was first described in a medical journal in 1912, and the man who described it had trouble finding a second case. Doctors had been opening chests for 300 years. They had dissected kings, paupers, drunks and the obese, and the blocked coronary artery was a rarity you wrote up. A young Boston cardiologist started practising in 1911. He later said he did not see his first heart attack patient until 1921, and then they came in a flood. By 1950 it was the biggest killer in the United States. By 1960, in Britain. Victorian England ate butter, dripping, suet, bacon and cream, and smoked like a chimney, and the coronary ward did not exist. The Masai lived on milk, meat and blood, and the doctors who went looking in the 1960s could not find heart disease among them. So what arrived between the dissecting rooms of 1900 and the coronary care units of 1960? Crisco launched in 1911. Cottonseed oil hardened into a block that looked like lard. Margarine followed it into every kitchen. By 1960 a quarter of American fat came out of a seed press that had not existed in 1900. The seed oil goes into your blood on the LDL particle. It is the part of the particle that oxidises. The oxidised particle is what the artery wall takes in. The cholesterol was in the butter for a thousand years and the artery stayed open. Then the fat changed, and a disease nobody had heard of became the way most people die. The guideline blames the butter. The butter has an alibi going back to the Bronze Age.