Explaining the Neolithic Demographic Transition

Three main questions are raised in this chapter. 1. The part of the signal of the NDT which is demographically identifiable, based on the proportion of the immature skeletons in cemeteries, shows that a baby-boom occurred and, beyond that, with the onset of the change in the economic system, a fertility transition towards high values also occurred. What was the biodemographic cause of this fertility explosion, beyond the proxy variable represented by sedentarism? The cause is a major shift in the maternal energetics of farming communities relative to mobile foragers. In the energy balance there was (i) on the intake side, an underlying trend towards a reduction in low-calorie food from hunting and fishing, and a correlative increase in high-calorie food from agriculture, (ii) on the expenditure side, a reduction in the physical energy devoted to mobility and the maternal stress of child transportation. 2. The NDT is detectable from a signal representing a fertility transition, but the transition relating to mortality is missing and must be inferred. If, during the fertility transition, mortality had remained the same as in the preceding forager period, then the population would have grown infinitely. The assumption of unchanged mortality during the entire fertility transition is therefore not realistic. Mortality, in its turn, must have begun to rise well before the end of the fertility transition. But when? Why? One of the answers consists of a model where, except at the start of the process, birth and mortality rates rise more or less simultaneously, bringing about a typical rate of increase for pre-industrial populations of slightly above zero. 3. According to the level and speed of the population growth, what should we expect in terms of population structure? What are the expected effects of this growth, not only on the population in numbers but also on age distribution, the distribution and structure of families, the distribution of households and on family systems?