The age of the sword

By Razib Khan | October 17, 2013 2:35 am

assyria

Credit: Aviok

“Think not that I am come to send peace on earth: I came not to send peace, but a sword.” -Matthew 10:34

“There were giants in the earth in those days…when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.” -Genesis 6:4

Seven years ago I wrote a short post, Why patriarchy?, which attempted to present a concise explanation for the ubiquity of what we might term patriarchy in complex societies (i.e., not “small-scale societies”). Broadly speaking my conjecture is that social and political dominance of small groups of males (proportionally) over the past several thousand years is an example of “evoked culture”. The higher population densities in agricultural societies produced a relative surfeit of accessible marginal surplus, which could be given over to supporting non-peasant classes who specialized in trade, religion, and war, all of which were connected. This new economic  and cultural context served to trigger a reorganization the typical distribution of power relations of human societies because of the responses of the basic cognitive architecture of our species inherited from Paleolithic humans. Agon, or intra-specific competition, has always been part of the game on human socialization. The scaling up and channeling of this instinct in bands of males totally transformed human societies (another dynamic is elaboration of cooperative structures, though this often manifests as agonistic competition between coalitions of humans).

To get a sense of what I mean when I say transforming, consider this section of an article in The Wall Street Journal which profiles the wife of one of the 2012 New Delhi gang rape:

Some people blame the December gang rape and similar attacks in part on a collision of traditional social expectations—commonplace in rural areas—and the modernity of India’s cities, where rural migrant workers encounter the values of urbanites living by a different set of rules. During the brutal Delhi assault, for instance, the attackers accosted the woman and the young man she was with, asking why they were out together in the evening, the young man told the court.

Speaking about the events of that night, Ms. Devi says she doesn’t understand how a woman could be out for the evening with a man who wasn’t her husband.

The normalcy of this sort of ‘mate guarding’ is taken for granted in many ‘traditional’ societies. You see it reflected in the 1995 film First Knight, where King Arthur tries Lancelot and Guinevere for treason based on a kiss (dishonor to the realm). I won’t go into excessive psychoanalysis, but end by saying that the emergence of radical inequality and stratification with complex societies transformed instincts shaped in small-scale bands where petty conflicts were no doubt the norm. To my knowledge the literature from small-scale societies tends to imply a relatively more relaxed, even modern, attitude toward sexuality than one can see in world of the Eurasian Ecumene.

At this point you might be curious as to the point of reviewing this conjecture. Perhaps I will bring to the fore historical and archaeological evidence which might support this model? No. Rather, I contend that the evidence of this radical reshaping of human power structures, which led to the emergence of patriarchy as we understand it, is reflected in the phlyogenetic history of our species. Two papers illustrate the differing patterns which one sees in the maternal lineage, mtDNA, and the paternal lineage, Y chromosomes.

First, Y Chromosomes of 40% Chinese Are Descendants of Three Neolithic Super-grandfathers:

Demographic change of human populations is one of the central questions for delving into the past of human beings. To identify major population expansions related to male lineages, we sequenced 78 East Asian Y chromosomes at 3.9 Mbp of the non-recombining region (NRY), discovered >4,000 new SNPs, and identified many new clades. The relative divergence dates can be estimated much more precisely using molecular clock. We found that all the Paleolithic divergences were binary; however, three strong star-like Neolithic expansions at ~6 kya (thousand years ago) (assuming a constant substitution rate of 1e-9/bp/year) indicates that ~40% of modern Chinese are patrilineal descendants of only three super-grandfathers at that time. This observation suggests that the main patrilineal expansion in China occurred in the Neolithic Era and might be related to the development of agriculture.

Second, Analysis of mitochondrial genome diversity identifies new and ancient maternal lineages in Cambodian aborigines:

Cambodia harbours a variety of aboriginal (and presumably ancient) populations that have largely been ignored in studies of genetic diversity. Here we investigate the matrilineal gene pool of 1,054 Cambodians from 14 geographic populations. Using mitochondrial whole-genome sequencing, we identify eight new mitochondrial DNA haplogroups, all of which are either newly defined basal haplogroups or basal sub-branches. Most of the new basal haplogroups have very old coalescence ages, ranging from ~55,000 to ~68,000 years, suggesting that present-day Cambodian aborigines still carry ancient genetic polymorphisms in their maternal lineages, and most of the common Cambodian haplogroups probably originated locally before expanding to the surrounding areas during prehistory. Moreover, we observe a relatively close relationship between Cambodians and populations from the Indian subcontinent, supporting the earliest costal route of migration of modern humans from Africa into mainland Southeast Asia by way of the Indian subcontinent some 60,000 years ago.

The scientific methods here are straightforward, or at least tried and tested. The main gains here are in terms of raw numbers and sequencing. Basically this is the extension of phylogeographic work which goes back 20 years, but on steroids. As such one should be cautious. The old phylogeography literature has turned out to be wrong on many of the details. But that’s OK, there’s still gold there, you just have to look.

The broad scale implication of the paper on Chinese Y chromosomal diversity is obvious. Like the Genghis Khan modal haplotype these are lineages which exhibit a ‘star-like phylogeny.’ They explode out of a common ancestor in short order, with few mutational steps. This explosion is simply a reflection of very rapid population growth. The skewed distribution of Y lineages here (i.e., three lineages representing nearly half the population) indicates to me a pattern where elite males tend to be much more fit in reproductive terms than the average male. Rapid population growth may have been correlated with a high rate of extinction of Y lineages due to “elite turnover“.

mtDNA

Citation: Zhang, Xiaoming, et al. “Analysis of mitochondrial genome diversity identifies new and ancient maternal lineages in Cambodian aborigines.” Nature Communications 4 (2013).

The second paper looks at mtDNA, the maternal line. There are some specific results which are interesting. In line with Joe Pickrell’s TreeMix results it does look like Cambodians and Indians share deep ancestry dating to the Paleolithic. The PCA to the left shows the relationships of populations in relation to their haplogroups, and one clear finding is that Cambodians tend to cluster with Indians, and not Northeast Asians. This result is not unsurprising. As I’ve noted before on mtDNA lineages South Asians are closer to East Eurasians than they are to West Eurasians. The result for the Y chromosomes is inverted, while autosomes are somewhere in the middle. In addition the results above show that South Chinese Han mtDNA tend to occupy the same part of the plot as the Dai, who are related to the Thai people of Southeast Asia. In contrast the few North Chinese Han tend to cluster with Tibetans and Altaics. Could Sinicization have been male mediated? There’s been circumstantial ethnographic evidence which points to this (e.g., some Cantonese marriage practices may reflect assimilation of Dai women).

The big picture result to me is that it illustrates the discordance between migration patterns of males and females over the past 10,000 years due to the rise of agriculture and its offspring, patriarchy. I hold that there was no hunter-gatherer Genghis Khan. Such a reproductively prolific male, worthy of an elephant seal, is only feasible with the cultural and technological accoutrements of civilization. ~20,000 years ago Temujin may have had to be satisfied with being the big man in a small clan. Thanks to various ideological and military advancements by the year 1200 AD you saw the rise to power of a man who could realistically assert that he was a ‘world conqueror.’

Male_gorilla_in_SF_zoo

Credit: Brocken Inaglory

Of course I do not believe that the world before agriculture was static. On the contrary the Chinese Y chromosomal paper reports an inferred pattern of lineage extinction which is regular and consistent. But civilization escalated the magnitude of genocide, and in particular androcide of the losers in the games of power. The relative continuity of mtDNA across vast swaths of southern Eurasia is a testament to the fact that the lineages of the ‘first women’ still persists down among the settled agricultural peoples, whose genomes have been reshaped by untold sequences of conquests and assimilations. While female mediated gene flow can be imagined to be constant, continuous, and localized, I believe that male mediated gene flow has a more punctuated pattern. It explodes due to cultural and social innovations, such as the horse or Islam, and long standing Y chromosomal variation which has emerged since the last wave of conquerors is wiped away in a single fell swoop. Obviously this has an effect on the total genome, and I suspect that in some cases repeated male mediated expansions have resulted in striking discordances between the autosomal and mtDNA lineages. You see this in Argentina, where Native American mtDNA seems to persist to a higher degree than autosomal ancestry because of male skew of European migration. And it looks to be the case in Cambodia, where non-North East Asian autosomal ancestry seems to be present a lower fraction than the equivalent mtDNA.

With the rise of ubiquitous genomic typing and sequencing the geographical coverage will be fine grained enough the broad patterns, and specific details, will become clear. Then we will finally be able to understand if the societies fueled by grain truly ushered in the age of the domination of the many by the few. How easily does a scythe become a sword?

  • Juan

    I’ll give you this example about an ancestor of mine, Diego de Rojas, governor of Charcas. He came to the Americas en 1522 and married a local woman. His daughter (1/2 amerind) María married the spanish captain Álvaro Vélez de Alcócer. They had a daughter (1/4 am), Elizabeth, who married the spanish conqueror Lope Bravo de Zamora. They had a daughter (1/8) named Catalina who married the spaniard Francisco de Alba, a governmet officer. On February 13, 1682, their daughter Juana Juliana (1/16), married the italian merchant Giuseppe Isole. Their daughter Lucía (1/32) married the spanish general Juan Alonso Gonzalez de Aragón. Their daughter Gregoria Gonzalez de Islas (1/64) married the galician merchant Francisco Villarino Varela.
    Their daughter Josefa Villarino Islas (1/128), married the italian merchant Angelo Castelli Salomone, and their son Juan José Castelli (1/256), was a hero of the Argentine Independence.
    He was over 99,5% European, but he had an american maternal haplogroup.

  • Dmitry Pruss

    Scythes-to-swords may not be the best metaphor when one of the examples is Genghis and his descendants who didn’t plow. And the phenomena of androcyde and female-hoarding are relative common across species anyway, and it’s been practiced in some habitats of our own species where the societies were very granular and not very dense (like in New Guinea). What might have changed their scale in the human species might not be an evolution of the trait per se, but rather increases in the density / accessibility of females.

    So I suspect that three star-like haplotype clusters of China AND the Genghiside cluster just attest to a habitat peculiarity in this corner of the world. The heartland of Genghis suffered through periodic overpopulation episodes, and unleashed waves of conquerors on its neighbor, with an astounding regularity, every few hundred years (before Genghis and even after). The earliest of these radiating conquests are attested in history in the middle of first millennium BC, but it’s reasonable to hypothesize that the natural cycle of large-scale conquests has been going on for much longer. If some of these episodes happened to be more severe than the others, then it may not be surprising that we ended up with these start-like clusters of Y chromosomes today.

    • razibkhan

      were very granular and not very dense (like in New Guinea)

      PNG highlands were/are quite dense last i checked. do you know something about ethnography that i don’t?

      The heartland of Genghis suffered through periodic overpopulation episodes, and unleashed waves of conquerors on its neighbor, with an astounding regularity, every few hundred years (before Genghis and even after).

      malthusian conditions are a particularity of that part of the world and that time? what do you think accounts for r1a or r1b?

      • Dmitry Pruss

        Yes, I anticipated your comment on relatively high population per sq km in the New Guinea Highlands (not island-wide but it is still unusually dense for their location and technology). “Granularity” means that the society is split between thousands of unfriendly tribes and villages, and the terrain is crisscrossed by mountain ridges, gorges, and jungle lands. What matters for a female-hoarder is not how many victims are per square mile, but how many of them are within a week’s march. When normalized by the size of the area accessible within one season of a military campaign, New Guinea islands aren’t female-rich at all.

        Re: Mathusian conditions and “something you might not now”… I’m not sure how familiar you’re with this phenomenon of periodic conquests radiating from today’s North China and Mongolia for thousands of years. I wouldn’t wager that simple old-fashioned Malthusianism provides a complete explanation, but the repetitive, stereotypical nature of these outbursts is truly remarkable. Let me know if you need a primer on this phenomenon, and references – as I said, the core explanations will be open to speculation; all I wanted to show was that grain-producing hierarchies aren’t the only possible explanation of Y-haplotype stardom, and that in fact different mechanisms have been well attested.

        • razibkhan

          i know more chinese and central asian history than most people have forgotten. so what references are you talking about? i know a lot of roman history too. the differences are not as stark as people make them out to be from what i can tell (e.g., collapse of population in the balkan hinterlands and in the wake of the hunnic depredations of the 5th century vs. what happened in the north china plain after the collapse of the latter han).

          your verbal argument about PNG sounds persuasive. i wish i have time to run some simulations.

          • Dmitry Pruss

            Then your C Asia sources may be more systematic than mine :) My haphazard knowledge of migrations of warlike nomads in the region mostly comes from L. Gumilev who at the beginning of his career wrote a groundbreaking tome on VIth c. AD Göktürks, but who later published a whole slew of increasingly fringe books on ethnogenesis in general, and cultural and genetic role of the Turkic peoples in the Middle East and Eastern Europe in particular. I couldn’t care less about some of Gumilev’s grand theories, but I remember some of the facts well. I.a. it appeared that conquests of the Steppe people of very different epochs always included the same stereotyped military and tribal dualism of Right and Left Wings, one ravaging China, another spreading far West. He was a very intriguing personality BTW, having suffered much oppression and war, and having received a good deal of his education behind the barbed wire. Check him out, you might be interested. Of course I had personal reasons to peruse his work, because I took part in expeditions to the land of Telengits (speakers of very archaic Turkic in the mountain refugia of Altai), because I liked poems of Gumilev’s father who was shot by the Reds when his son was still a toddler, and perhaps also because, doh, I have some Genghisids in my own extended family :)

            Post-Hunnu population collapse in SE Europe is interesting to compare; I suspect that Huns were too far from their bases to make that much demographic difference, and that plentiful local mountain refugia played a role, but yes, there’s something about it.

        • MrJones

          “”grain-producing hierarchies aren’t the only possible explanation of Y-haplotype stardom”

          Doesn’t the Genghis Khan example require a grain-producing hierarchy – just not the one that did the conquering?

  • razibkhan

    not male. but males manifest more violence (probably due to strength differences). re: bands, the issue is scale. i think male band-forming dynamics scale more easily than female coalition-forming (females relying more on inter-personal social intelligence, males on dumb-but-easy heuristics).

    • http://entitledtoanopinion.wordpress.com TGGP

      Surprised you didn’t mention the big biological difference that sperm is cheap, eggs are expensive. Variance for male reproductive success is much higher (no female Genghis Khan), so it’s in their interest to take bigger risks.

  • omarali50

    Interesting line: “cultural and social innovations such as the horse AND ISLAM”. What innovative features of Islam were you thinking of when writing this line?

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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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