Born in Britain in 1919, independent scientist and environmentalist James Lovelock has worked for NASA and MI5. Before taking up a Medical Research Council post at the Institute for Medical Research in London, Lovelock studied chemistry at the University of Manchester. In 1948, he obtained a PhD in medicine at the London School of Hygiene and Tropical Medicine, and also conducted research at Yale and Harvard University in the USA. Lovelock invented the electron capture detector, but is perhaps most widely known for proposing the Gaia hypothesis. This ecological theory postulates that the biosphere and the physical components of the Earth form a complex, self-regulating entity that maintains the climatic and biogeochemical conditions on Earth and keep it healthy.