Finally, one of the most neglected causes of change has been
human fecundity...Human societies, however, are able to respond to population
pressures with cultural innovations. Ideological changes to customs
or in laws, for example, may cause people to delay the age at which they
marry, or legitimate such practices as abortion. Alternatively, technological
changes may provide the population with better methods of contraception,
or enable them to produce more food to keep a growing number of children
alive and well (1991, p. 54).