Evolution, Demography and Inheritance

I have been reading some popular works on anthropology and evolutionary psychology and am getting increasingly fed-up with their frequent assumption that men instinctively want to sleep with as many women as possible so that they can have as many children as possible. Even excluding the modern Western world, in which many men do not want to have children (or at least not be held responsible for them), there doesn’t seem to me much historical evidence that men wanted to father as many children as possible.

Firstly, and most brutally, in many contemporary and historic societies, girls have been undervalued and sometimes even killed or abandoned by their fathers. For the survival of a man’s genes, a female child is valuable; in many patrilineal societies, she’s not valuable because she doesn’t preserve his “name”. But I don’t think the historic evidence is particularly strong even for the weakened hypothesis that men want to sleep with as many women as possible so that they can have as many sons as possible. In societies where elite men have large harems, for example, women are selected for these harems, based on their beauty (Gerda Lerner, The Creation of Patriarchy, pp. 70-71 cites letters about this from King Zimri-Lim of Mari in Syria from the eighteenth century BC). This implies that such successful men are less interested in sleeping with as many fertile women as possible and more concerned with sleeping with women they find sexually attractive.

Clay tablet recording activity of Zimri-Lim (from Wikimedia)

Most men, however, aren’t as prosperous as Zimri-Lim. One of the most basic constraints on how many children you choose to father is how many you can afford to support. This is so even in historical periods without effective contraception or abortion. Abandonment of the mother and/or child, adoption and even infanticide have always been possible options. But in most past societies, a child whose father didn’t support them was either not going to survive into adulthood, or was going to have its chances of marriage and reproduction severely limited. So in evolutionary terms, this is not likely to be a successful strategy.

But there’s also another issue in societies with private property: the question of what the children (especially the sons) inherit when their father dies. Whether it’s land or livestock, at some point there’s likely to be a sharing-out of resources, even if it’s postponed for a generation. And at that point, having too many sons can again be a problem, because it means splitting resources into smaller shares or excluding some sons from any inheritance. There’s been interesting work by Ruth Mace at UCL trying to model how African pastoralists decide whether or not to have more children and how many sons to give wealth to.

This concern to get the “right” number of heirs may also explain various family options which develop.  For example, the institution of concubinage, already visible in the Code of Hammurabi from around 1750 BC, may have developed precisely because concubine’s sons could be conditional heirs, who were normally excluded from inheritance, but could be made heirs if one was needed.

Ruth Mace states in another article (p.447):

It has long been recognized that maximizing reproductive success is not necessarily about maximizing fertility alone, going right back to the pioneering work of ornithologist David Lack [in 1954].

So why, sixty years on, are some authors still writing statements such as:

A man can have a nearly unlimited number of children – in theory he can beget several children every day – while a woman’s capacity is limited to one child per year under optimal conditions, and moreover in many societies many children die before they grow up. From the perspective of human reproduction, one may state that sperm is cheap while eggs are expensive.

(Quote from Thomas Hylland Eriksen, Small Places, Large Issues: An Introduction to Social and Cultural Anthropology. 2nd ed, 2001, p. 108)

Sperm may be “cheap”, but raising a child to adulthood is almost always expensive for fathers as well as mothers, if they’re going to ensure their line’s continuation. I’m currently trying to work out what kinds of evolutionary effects it’s worth considering when thinking about patriarchy in western Europe in the common era. The badly flawed evolutionary  accounts of male humans that still turn up frequently, and which ignore so much historical evidence, don’t seem to me a reliable basis for making further hypotheses about male behaviour.















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