My choice for the most important invention? The contraceptive pill.
Why? Well, there are, of course, the well-rehearsed answers to that question. The pill did indeed fertilize the sexual liberation of the sixties, did stimulate feminism and the consequent erosion of conventional family structure in Western society — perhaps the most significant modification in human behaviour since the invention of shamanism. It did help to change our concept of the division of labour, to foster the beginnings of an utterly different attitude to the social role of women. But, arguably the important sequel of the pill is the growing conception that our bodies are servants of our minds, rather than vice versa. This relatively low-tech invention has triggered a cultural and cognitive revolution in our self-perception. It has contributed to our ability to accept organ transplantation, the notion of machine intelligence, gene therapy and even, eventually, germ-line genetic manipulation. It has shifted the quest of human beings from controlling their physical environment to controlling themselves — their own bodies and hence their physical destinies.