Polygamy and human evolution: maybe it's agriculture

By Razib Khan | October 1, 2010 12:11 pm

Eric Michael Johnson has a fascinating piece in Psychology Today, Sex, Evolution, and the Case of the Missing Polygamists. I want to spotlight a few paragraphs:

Keep in mind that in terms of interpreting such genetic evidence we are of necessity confined to a fairly recent time depth (and remember, by “recent” someone like me means the last 10,000 years or so). For this time period multiple lines of evidence do indeed suggest that humans were moderately to extremely polygynous and that women were moving between groups more than men were.

However, humans have been around for far longer than 10,000 years, with conservative estimates placing the emergence of modern Homo sapiens at about 200,000 years ago. A genetic record extending back 10,000 years is remarkable, but it’s essentially adding only three more novels to our existing timeline. There is also something very important to consider that dramatically influenced human behavior within the last 10,000 years: the invention of agriculture. Prior to about 12,000 years ago all humans were hunter-gatherers and lived a migratory existence. With the advent of farming some human societies began to remain sedentary for the first time in our history. This change had serious impacts on human life and behavior. Just as Alzheimer’s dramatically altered the content of Agatha Christie’s work, so agriculture radically transformed human society and, by consequence, sexual behavior.


Cultural norms can be protean, but we humans have short time horizons. One model of human history which I am convinced of is that many “traditional” social arrangements which we view as old-fashioned and timeless are actually innovations which arose during the shift to agriculture, which allowed for the birth of complex societies in many regions of the world. Not only did customary norms shift, but the nature of customary norms varied across the society as class stratification emerged. Solemnized marriage between elite lineages may seem normative through much of the history of civilization, but this was obviously going to be much less of a factor for most of the peasantry.

Both hunger-gatherers and farmers lived on the Malthusian margin. Excess population swallowed any gains in economic productivity. But obviously the change in population density and mode of production resulted in qualitative differences between the two classes of societies, especially for agriculture elites who could much more efficiently extract rents to sustain a more affluent lifestyle of leisure. Now much of the world is moving to the next stage: agricultural values combined with the reality of post-Malthusian consumer societies. Institutionalized marriage between a man and a woman in classic a bourgeois sense in the modern West is a hybrid of of values. No longer so much a bond between family lineages, as it was for pre-modern elites, nor is it an ephemeral and common law arrangement as it may have been for the masses (in part because of shorter life expectancies).

Finally we should look past the West, and see that changes are occurring all the across the world as cultures are generating values “mash-ups.” Over the 20th century in South Asia “Sanskritization” has taken hold and practices such as dowry which were normative among upper class groups have now spread throughout the culture. The decline of matrilineal social structures in parts of Southern India in favor of more conventional national implicit or explicit patrlineage is part of the horizontal homogenization through space which is concomitant with the vertical integration of values across class lines. Similarly, the rise of “Islamic Orthodoxy” and adherence to sharia can only exist in a regime of economic surplus, as punctilious attention to religious law is often not possible for families on the boundary between subsistence and starvation.

Our “software” is in many ways a compound of deep evolutionarily encoded instincts, along with more recently crystallized norms and values which “have always been.” But we’ve gotten a massive upgrade in the “hardware,” and the software is adjusting and expanding.

CATEGORIZED UNDER: Anthroplogy, History
MORE ABOUT: Anthropology, Sex
  • bioIgnoramus

    Razza, I invite you to award a Strange Comparison of the Year Prize to “Just as Alzheimer’s dramatically altered the content of Agatha Christie’s work,…”. Unless you’ve seen an odder one, of course.

  • Katharine

    Similarly, the rise of “Islamic Orthodoxy” and adherence to sharia can only exist in a regime of economic surplus, as punctilious attention to religious law is often not possible for families on the boundary between subsistence and starvation.

    But whither the rise of ‘Islamic Orthodoxy’ and other religious orthodoxies at all once the economic surplus occurred?

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  • Tom Bri

    Razib, several times recently you have remarked that pre-agriculture humans lived at the Malthusian Limit. I wonder if this is true. What I know of the bone analysis evidence shows very well-fed people, pre-agriculture (though with evidence of periods of scarcity).

    I suspect that other things besides food resources limited population.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    i think they probably killed each other more. so no, not quite as *tight* against the lid as agriculturalists. they “self limited” :-) but compared to developed societies, yes, they basically did.

  • omar

    After reading Razib for a couple of years I understand that statements are usually supported by evidence, so this is not to imply that the statement is wrong; I am just curious to know the references for “spread of dowry into the lower classes” being a recent phenomenon? What part of India is that from? And how recent is it?
    Anecdotal evidence is very poor evidence, but in our village in central Punjab, people of all classes seem to have been obsessed with dowries, though the amounts were small among the poor. Is that a recent phenomenon? Also, is it possible that actually giving a dowry was not that common for the really poor, but some notion of its desirability was still present?
    Just curious.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    brideprice used to be common for lower caste/less sanskritized groups circa 1900. by 2000 it basically disappeared. you can probably find it on a lit search, but that’s the time frame. the british funded anthropological surveys of “indian communities” so you can see the overall trends.

    obviously the practices spread from upper to lower castes, and from the center-north to the rest of the nation, more or less.

  • The Dude

    Polygamy and human evolution: maybe it’s agriculture? Perhaps it’s climate.

    It was the 5- to 10-fold reduction in climatic variability after the Younger Dryas which made agriculture viable in the first place. Skateholm (Sweden) shows evidence of sedentism and violence prior to the receipt of agriculture in Scandinavia.

  • Zora

    Marshall Sahlins, before his French structuralist phase, published some good essays on “primitive” economics, arguing that hunter-gatherers worked fewer hours than modern wage slaves. Also that in small-scale societies such as the Fijian island he studied. people worked just hard enough to meet ritual obligations and keep up with neighbors. Not any harder.

    What kept population numbers down, IMHO, wasn’t the average state of things, but periodic droughts, blights, hurricanes, etcetera. Liebig’s Law of the Minimum. It’s easy to forget that these days, when the Red Cross shows up to hand out relief supplies (as they did after a hurricane hit the small Tongan island on which I was living). My Tongan dictionary, compiled more than 100 years ago, is full of plant names followed by the observation, “eaten in times of famine”. Us Kauvai folk didn’t have to experiment with any of those. We had Red Cross flour.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    Marshall Sahlins, before his French structuralist phase, published some good essays on “primitive” economics, arguing that hunter-gatherers worked fewer hours than modern wage slaves. Also that in small-scale societies such as the Fijian island he studied. people worked just hard enough to meet ritual obligations and keep up with neighbors. Not any harder.

    the anthropology on this is a bit confused, but fwiw the same argument has made for peasants. judging by the number of saint’s days, etc. the main issue is that on the malthusian margin it isn’t as if people had enough to eat where you could expect them to put lots of strenuous labor input anyhow. basically they may have just put enormous inputs into particular times of the year.

    that being said, i do think that moderns tend to not realize that “leisure” in a pre-modern society may have been pretty difficult. the “starving times” when the larder is nearly done and there’s a temptation to go the seed corn.

  • Pat

    Absence of polygamy may be thought of as an advancement in human society to prevent accelerated evolution due to random genetic pairings that may tend to hasten variability, and the chaos that otherwise, genetics would tend to follow.

    When reproduction is predictable, it is manageable; when it isn’t, it amounts to chaos, genetically, and few pairings can result in families within the context of the long term commitments that humans rely upon to form the anchor of society, to aid, and to protect each other.

    In a polygamous world of the past, that impulse would not have been present, except to the extent when all were attacked as in wars. Predictable agriculture and predictable industry aids predictable human society, socially, cognitively, and biologically, and therefore, contributes more to progressive human society than not. It may also reduce the opportunity for harmful disease which would otherwise inflict rampantly promiscuous society.

    For technological societies to advance, some measure of safe, secure, and predictable routine is required in order to form the rudiments of government and industry to drive societies forward. That is a part of the latent struggle of developing societies which have no yet reached a predictable culture and continue to mine the pleasures of polygamy, and the downside risks and problems associated with it.

    While polygamy may seem harmless, it is actually quite harmful to society in that manner, not to mention the fact that by setting an example of polygamy in others, the norm can become one that there is no reason not to embrace by human society, thereby sacrificing the progress of all for the preferred deviance of some.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    just a note to readers. i agree with pat that polygamy is not optimal (mostly cuz of my own values and how i think humans should flourish). but that comment is really a blog post.if you’re going to go “long form” please increase the ratio of data/facts. an extended argument isn’t really appropriate.

  • manju

    Over the 20th century in South Asia “Sanskritization” has taken hold and practices such as dowry which were normative among upper class groups have now spread throughout the culture.

    Not sure dowry system was part of Brahmanical ritualism when MN Srinivas coined that word. That appears to be Feudalization than Sanskritization.

  • Mike Cope

    2 points

    We also have to remember that predation was a significant factor in keeping human populations down. Lions are a formidable foe, and compete with human males for the same prey, and humans don’t gain a technological advantage over them until the advent of metal weapons. The Bleek & Lloyd archive records numerous instances of /Xam people being killed in the nineteenth century.

    People wanting to study the difference between agricultural and nomadic societies could do well to look at the transition as it happens in Egypt, about which quite a lot is known. It happens very swiftly, and coincides quite precisely with the arrival of grain.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    is there a paper you’d point to as an entry into the literature on the second point?

  • Mike Cope

    A good place to start would be:
    Wengrow, David (2006). The Archaeology of Early Egypt:
    Social Transformations in North-East Africa, c. 10,000 to 2,650
    BC. New York: Cambridge University Press. ISBN 0521835860.

  • DavidB

    There’s an old but still useful book on ‘The Population Problem’ by A. Carr-Saunders. (Useful for facts about practices in various cultures, not for C-S’s theories.) Among traditional hunter-gatherers the average family size was small due to prolonged lactation and frequent infanticide. A family could not support more than one or two small children at a time, and during food shortages the children would be the first to go.

    As for polygamy, Carr-Saunders doesn’t say much about it, but other sources suggest that moderate polygamy (i.e. men with 2 or 3 wives) was not uncommon among hunter-gatherers. Among Australian tribes the older men tended to monopolise the fertile women, while younger men had to make do with pre-teen children.

  • Tom Bri

    ‘eaten in times of famine’

    I lived a couple of years in a small mountain village in Guatemala. The second summer there was a bean shortage, and corn was short, none in the market town or very expensive. People began extending their diets with various ‘weeds’, and eating things normally fed to animals. This lasted about a month, until the harvest started. Lucky for them it was a decent harvest so there was no actual starvation. But they were close.

    Malthusian limits apply on the margins. A single bad year will set the limit for an entire generation, so populations at the limit may not appear to be there most of the time. So, maybe I am wrong about prehistoric hunter-gatherers. A few drought years per generation may have set the Malthusian Limit, even if generally there was plenty of food, as reflected in the skeletons. I am looking forward to seeing more fine-grained bone analysis.

  • kirk

    Jeez Jared Diamond only scooped this headline by, like, 20 years with “The Third Chimpanzee”. Just sayin.

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  • Violet in Twilight

    I wonder about Bride Price being common among lower castes. From this (Kanya sulkam, http://en.wikipedia.org/wiki/Kanyasulkam), it is known to be common among Brahmins (priestly class in particular) in South India circa 1900.

    There was a lot of social reformation to get rid of Bride price and some of that literature used to be a part of compulsory readings during my schooling.

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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