Joint memory is defined as the property of a social group in actualizing its own past transformations. It may result from the coupling of individual memories or be inscribed in the external environment. The concept of joint memory becomes heuristic when it subsumes an ensemble of social processes that are sufficiently integrated to be treated as an entity belonging to the real world. In social insects, colonies can perform action-perception loops which give rise to collective outcomes based on past experience; selective pressures could favour individual behavioural algorithms the combination of which provides a historical record organizing activities both in space and time. In contrast, social groups do not appear sufficiently autonomous in most vertebrates for joint memory be more than a way of seeing collective performances. However, in human beings, the development of external representations has made possible the growth of a socially distributed cognition; the accumulation of epigenetic events through cultural processes produces a set of material and symbolic products that feed back upon the conditions of evolution of the species.