payment (bride wealth) needed at the end of their sons’ development and perhaps equal to the summed previous investment to establish sons on the marriage market. The flow of stock through families that are both bride wealth receivers and givers helps maintain the system at the same time that it creates problems for families with unfavorable ratios of sons to daughters (Borgerhoff Mulder, 1998).
Finally and most significantly, there is suggestive evidence that for the first time humans began to reproduce at levels that may not maximize the number of descendents with the appearance of extrasomatic wealth and its inheritance. Men appear to marry fewer wives than they could afford in the interests of providing each child with a greater endowment. In other words, male pastoralists may pit quality against quantity of children to preserve a lineage status and resource base rather than simply maximizing the number of descendents (Borgerhoff Mulder, 2000; Mace, 2000).
The rise of civilizations, beginning about 6,000 years ago in Mesopotamia and occurring at different times and places (e.g., Egypt in the Near East, the Aztec and Inca in the Americas, and India and China in Asia) marked a critical shift in how humans organized themselves in social systems and in relation to the environment (Betzig, 1993; Goody, 1976). These civilizations appear to have developed independently in response to local conditions without being the products of either conquest or diffusion. Despite this historical independence, they evidence significant similarities: (1) the presence of large stratified social groupings settled on particularly large and productive resource patches and (2) the appearance of social despots, men who use coercive political power to defend their wealth and reproduction and warfare to acquire more resource patches and slaves (Betzig, 1986). These two major effects flow from the nature of the resource patches.
The patches on which the first civilizations were settled had special qualities: (1) they were highly productive but set in environments where there was a rapid falloff to unproductive lands such as desert or forest and (2) these productive patches could not be intensively utilized without complex political organization as in regional irrigation systems. Political control and organization rested on the power of men. Although female nonhuman primates often form alliances with their female kin to protect and control access to the resources necessary for their reproduction (Isbell, 1991; Sterck et al., 1997), the reproductive benefits of resources are much greater for men than for women because of their impacts on polygyny. The