The dormitory of the pups’ compound was unchanged, with rows of sleeping niches down either side, dusty columns of reddish light slanting through the painted glass of the clerestory, the homely chatter of pups being prepared for sleep by their carers or visiting parents. After he had shown his collections of bird feathers and snail shells to his uncle, Amity settled in his sleeping niche and Pilgrim perched on a small stool beside him and they studied the bestiary. Here was a picture of a tiny tree rat from the Spice Islands which made its home in the hulls of a certain kind of nut. Here was the agile hopping rat from the hot dusty central grasslands, with its springy hind legs and the large naked shells of its ears, which it used to catch the warmth of the early-morning sunlight after the cold nights and radiate away excess body heat during the hottest part of the day. And here was a fierce lean mountain hob, and a tree glider from the cloud forests, with membranes of skin stretched between its fore and hind limbs, and a queen army rat and her attendant workers. Pilgrim asked Amity what they had in common, and explained, after the boy had made several guesses, that they shared a common ancestor which had looked something like the little spiny-tailed rats which had to be kept from the root stores, and lived in the long-ago time before the world had caught fire.

‘Two hundred thousand years ago, before there were people like us.’

‘Because there were ogres instead.’

‘That’s right. After the fire, the ogres were gone, or almost all of them, and so were most of the animals. But our little rat and her friends and relations survived, and her children and her children’s children found new places to live and new kinds of food to eat, because the animals which had once lived in those places and eaten that food were no longer around. And slowly, bit by bit, the rat’s children were changed by where they lived and how they made their living, and became different kinds of new animals.’

‘Is that a story, or is it true?’

‘It’s a true story. The best kind. My master discovered it by comparing the shapes of their bones and teeth.’