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.