The continuum concept is an idea, coined by Jean Liedloff in her 1975 book The Continuum Concept, that human beings have an innate set of expectations (which Liedloff calls the continuum) that our evolution as a species has designed us to meet in order to achieve optimal physical, mental, and emotional development and adaptability. According to Liedloff, in order to achieve this level of development, young humans—especially babies—require the kind of experience to which our species adapted during the long process of our evolution by natural selection. For infants, these include, for example, that they experience:
Liedloff suggests that when certain evolutionary expectations are not met as infants and toddlers, compensation for these needs will be sought, by alternate means, throughout life—resulting in many forms of mental and social disorders. She also argues that these expectations are largely distorted, neglected, and/or not properly met in civilized cultures which have removed themselves from the natural evolutionary process, resulting in the aforementioned abnormal psychological and social conditions. Liedloff's recommendations fit in more generally with evolutionary psychology, attachment theory, and the philosophy known as the Paleolithic lifestyle: optimizing well-being by living more like our hunter-gatherer ancestors, who Liedloff refers to as "evolved" humans, since their lifeways developed through natural selection by living in the wild.