Testing adaptiveness of culturally determined behaviour: do Bushman women maximize their reproductive success by spacing births widely and foraging seldom?

Abstract

The proposition that adaptive success for Bushman women lies in having as many babies as they can successfully raise is explored by examining possible disadvantages of a shorter birth interval than the nearly 4 years currently experienced by nomadic Bushman women. The basic model considers the interaction of birth spacing food requirements and back loads since foraging women carry children up to 2 or sometimes 4 years old on their expeditions and must also carry heavy loads of mongongo nuts over considerable distances in adverse climatic conditions. Results of preliminary calculations indicate that the back load of food plus babies increases sharply with a birth interval of less than 4 years but that it is remarkably level through a womans reproductive career with birth intervals around 4 years. Potential limits on how much a woman can carry and how often she can make foraging trips are discussed. The optimal strategy would be to have the largest family that could be fed adequately during the dry season within the limits of safe backloads. A framework for determining whether the optimal strategy would be represented by a 4-year birth interval is outlined but data limitations preclude a definitive test.