Of course, nothing comes out of nothing. I'd been thinking about ‘what if’ scenarios almost all my life. I grew up among the scientists — ‘the boys at the lab’ mentioned in the Acknowledgements are the graduate students and post-docs who worked with my father in the late 1930s and early 1940s at his forest-insect research station in northern Quebec, where I spent my early childhood.

Several of my close relatives are scientists, and the main topic at the annual family Christmas dinner is likely to be intestinal parasites or sex hormones in mice, or, when that makes the non-scientists too queasy, the nature of the Universe. My recreational reading — books I read for fun, magazines I read in airplanes — is likely to be pop science of the Stephen Jay Gould or Scientific American type, partly so I'll be able to keep up with the family dialogue and maybe throw a curve or two. (‘Supercavitation?’) So I'd been clipping small items from the back pages of newspapers for years, and noting with alarm that trends derided ten years ago as paranoid fantasies had become possibilities, then actualities. The rules of biology are as inexorable as those of physics: run out of food and water and you die. No animal can exhaust its resource base and hope to survive. Human civilizations are subject to the same law.