The "drifty gene hypothesis" was proposed by the British biologist John Speakman as an alternative to the thrifty gene hypothesis originally proposed by James V Neel in 1962. Speakman's critique of the thrifty gene hypothesis is based on an analysis of the pattern and level of mortality during famines. Despite much anecdotal evidence used to suggest that famines cause substantial mortality, Speakman suggests that where real data are available famines actually involve rather low levels of mortality and there is no evidence that fat people survive famines better than lean people. In fact, mortality actually falls mostly on groups such as the very young and very old where differential mortality in relation to body composition is highly unlikely.