This is a book about a rapidly developing idea that has very important implications both for evolutionary biology and for medicine and public health. It offers clues to a better understanding of the origins of many diseases and their prevention and also provides additional insights into important biological processes relevant to evolutionary and life-history theory.

Ideas in science do not often develop in a manner that Fleet Street would have us believe. Science is not normally about ‘breakthroughs’ and brilliant scientific insights springing from nowhere. It is a most unusual event for scientific understanding to arise in the ‘Eureka!’ mode, where a single scientist has a flash of inspiration, jumps out of his bath and runs down the street screaming with excitement. Imagine the streets of Boston or Oxford if science was really like that!

Most science is in fact rather boring, in that each advance in understanding is made by the painstaking and careful work of scientific teams operating in collaboration and competition (often simultaneously!) with each other. Their observations gradually provide greater insights into a particular field. Therefore scientific progress must be measured by a series of small steps – some experimental and some conceptual. It is most unfortunate that the media-driven perception of science on one hand, and the competitive nature of restricted research funding on the other, force scientists to hype and to present scientific progress as isolated ‘Eureka moments’.