The conventional wisdom about the development of human societies primarily concerns the interrelationship of technology and economics. In the “socio-cultural evolution” model, the earliest human societies consisted of hunters and gatherers, whose tools consisted of sharp implements for hunting animals and cutting edible vegetation. These hunters and gatherers were nomadic because they had to be on the lookout for food. Depending on the environment, the hunters and gatherers gradually learned how to use simple tools to grow food or how to domesticate and herd the animals, resulting in horticultural and herding societies. As the former developed more advanced technologies for turning up the soil, such as plows, they created a greater surplus, leading to more social inequality, the need to protect surpluses (or to grab those of others), and therefore to political societies and warfare. These agricultural societies lasted until factory production made possible the production of even greater surpluses. The mystery has always been, though, why people would make the transition to agricultural societies, since these usually relied heavily on single crop production, so that most “civilized” people suffered greater malnutrition, in addition to more oppression by elites than their tribal ancestors.
The socio-cultural view has a great deal in common with Rousseau’s description of the development of society: complex societies derive from fencing off property and (early civilization at least) was a fall from a better and more egalitarian state. Chagnon, though, draws on genetic ideas of “inclusive fitness” to offer a modified Hobbesian view, with the Yanomamö as empirical evidence. Tribal societies are basically kinship groups. Human beings have evolved to support and trust their kin because when people who share genes (kin) cooperate with each other, the shared genes are more likely to be passed on. Now, comes probably the most politically incorrect part of Chagnon’s argument: the related individuals who cooperate are mainly men who are related to each other, and they are cooperating in obtaining the means to pass on their genes, i.e., women. Chagnon argues that warriors in a tribal society don’t fight over material resources. They fight to grab or keep women.
Tribal groups tend to form larger and more complex alliances, still based mainly on kinship, because larger sets of warriors have an advantage over the smaller sets in the constant warfare. Agriculture does not lead to population growth; population growth, for the sake of efficacy in fighting, leads to the development of agriculture as a means of supporting more fighters (and, presumably, more specialized fighters as differentiation increases). Chiefs and kings emerge because the larger societies can’t be governed by informal, kin-based tribal methods.
One of the reasons I find Chagnon’s views plausible, as well as interesting, is that when I look at human history, in the recent past as well as the distant past, I see that warfare has been a driving force in both technological development and social organization. I am not sure that bride capture was as exclusive a motivation for fighting as Chagnon suggests, even from Darwinian logic. People do need access to resources, and competition for available food supplies is one of the primary mechanisms of natural selection. Still, warfare usually does have sexual dimension, even in modern conflict.