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Cultural Evolution

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51sdHZvYfTL._SX334_BO1,204,203,200_ Evolutionary theory famously predated the emergence of genetics by decades. Initially there was some conflict between the heirs of Charles Darwin and the first geneticists in terms of their mechanistic understanding of how evolutionary process occurs. Within a few decades though genetics and evolutionary biology were synthesized so that the former came to be integral toward understanding the processes and parameters which shape the character of the latter (see The Genetical Theory of Natural Selection). E.g., imagine attempting to understand the origins and maintenance of sexual reproduction without any genetic understanding of the determination of sex and its implications for transmission.

But obviously genes are not everything when it comes to phenotypes. In particular with humans, there are complex behaviors and social interactions which seem to be persistent, and perhaps adaptive, which may not be directly contingent upon any simple genotype-phenotype map. 41YXHblIQEL This is not to say that cultural and behavioral traits have no genetic basis. To give an example, religion is a complex phenomenon which is both universal and does not seem directly encoded in one’s genes. The search for a “god gene” is futile, because religion as a phenotype is mediated by innumerable other phenotypes, which themselves have complex genetic bases.

Though culture is contingent upon genes, exhibits a character which is separable from genetic evolution. In particular, dual inheritance theory explicitly acknowledged that human cultural variation over time and space is a function of the interaction between both cultural and genetic evolution. Though there are similarities between the two, and in fact the field of cultural evolution consciously utilizes much of the same formalism as population and quantitative genetics, the modes of inheritance and nature of the origination and perpetuation of variation of the two differ a great deal.

As a rule of thumb you can posit that genetic evolution is relatively slow and torpid in relation to cultural evolution, which is protean and quicksilver. Consider that lactase persistence or high altitude adaptations are the two fastest we know for human genetics, and they occur on 1,000 year time scales. Over a 1,000 year time scale takes you from Julius Caesar to Otto the Great. It takes you from first of the Mycenaean, to Athens of Pericles.

The differences between culture and genes are important to keep in mind when one is making predictions. I’m a big fan of the Eric Kaufmann book, Shall the Religious Inherit the Earth?: Demography and Politics in the Twenty-First Century. The model outlined within the book, higher fertility for religious people, ergo, the reemergence of religion, is logically plausible. But I always must remind me people that the same concerns were prevalent in France before 1850, with the arrival of more traditional Roman Catholics into a milieu which had notably secularized and undergone early demographic transition. Why is France today not a uniformly Catholic republic? First, there is history. The migration of Muslims from North Africa. But even more important, cultural evolution, as the descendants of Spaniards, Poles, and Italians, secularized.

9780226558271 There is though a difference between description, and formal modeling. The field of cultural evolution attempts to do the latter. There are several lay and specialist introductions to the field (just click some of the book links and you’ve find them all). It’s worth attempting to grapple with the domain in a more systematic way, because that’s the only way you can make predictions which make sense of the diversity we see around us.

A new preprint is an interesting addition to the literature, Gene-culture co-inheritance of a behavioral trait:

Human behavioral traits are complex phenotypes that result from both genetic and cultural transmission. But different inheritance systems need not favor the same phenotypic outcome. What happens when there are conflicting selection forces in the two domains? To address this question, we derive a Price equation that incorporates both cultural and genetic inheritance of a phenotype where the effects of genes and culture are additive. We then use this equation to investigate whether a genetically maladaptive phenotype can evolve under dual transmission. We examine the special case of altruism using an illustrative model, and show that cultural selection can overcome genetic selection when the variance in culture is sufficiently high with respect to genes. Finally, we show how our basic result can be extended to nonadditive effects models. We discuss the implications of our results for understanding the evolution of maladaptive behaviors.

The most relevant section is probably 3.2 Model 2: Cultural prisoner’s dilemma. If you don’t know what the Price Equation is, read the original paper. It will induce some clarity.

The fact that more variance in culture in relation to genes allows for selection to act more powerfully on culture, and arguably in a maladaptive manner from the gene-centric perspective, is no surprise. This preprint adds more precision and clarity. For adaptation to occur there needs to be heritable variation. One reason that cultural group selection is more plausible than genetic group selection is that genetic variation across demes is often very low. The Fst between racial groups may be 0.10 to 0.30, but it is not very common for such Fst values to be realized between two groups genuinely in competition. More often neighboring populations have much lower Fst values, though ancient DNA is suggesting that 0.05 to 0.10 values were maintained in some areas 5 to 10 thousand years ago. A simple population genetic rule of thumb is that one needs to have less than one migrant between two populations per generation for their genetic variation to increase, rather than decrease. In other words, minimal gene flow on a general scale quickly reduces between group genetic variance.

In contrast, cultural variation can be maintained because migrants can switch cultures, or, their genetic progeny can adopt the culture of one the parents in totality. In this way the later Ottoman Sultans and Umayyad rulers of Al-Andalus had been genetically transformed by generations of mixing with concubines derived from Europeans or Caucasians (i.e., those from the Caucasus), while remaining culturally very Turk and Arab respectively.

As noted in the preprint, this formal/theoretical avenue of research will allow for the development of a robust empirical research program. The data is out there.

• Category: Science • Tags: Cultural Evolution, Genetics 
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Though we often think of evolutionary processes as either matters of bones (i.e., paleontology) and genes (i.e., evolutionary genetics), that is not strictly true. There are other domains of study where evolutionary thinking and frameworks have been applied. In particular I’m thinking of evolutionary thought in the context of culture. This has a long history, and evolutionary models as metaphors are commonly bandied about, from Herbert Spencer to Richard Dawkins. But the reality is that there is little systematic and formal investigation of the topic. In the late 1970s to the middle 1980s six scholars attempted to change this. First, E. O. Wilson and Charles Lumsden in Genes, Mind, And Culture: The Coevolutionary Process. Arguably the most ambitious of the projects, Wilson and Lumsden have moved onto other things. Next you have L. L. Cavalli-Sforza and Marcus Feldman with Cultural Transmission and Evolution. By and large both authors have moved onto other things, though Feldman at least still produces some research in the area of cultural evolution. I asked Cavalli-Sforza about cultural anthropology’s reaction to this book in 2006. He responded:

I entirely agree that the average quality of anthropological research, especially of the cultural type, is kept extremely low by lack of statistical knowledge and of hypothetical deductive methodology. At the moment there is no indication that the majority of cultural anthropologists accept science – the most vocal of them still choose to deny that anthropology is science. They are certainly correct for what regards most of their work.

His pessimism about cultural anthropology was warranted in my opinion.

0226712842 Finally, you have Peter Richerson and Robert Boyd’s Culture and the Evolutionary Process. Both these authors were explicitly influenced by Cavalli-Sforza and Feldman’s ideas (I believe they also took courses where Feldman was an instructor at Stanford to get up to speed on formal evolutionary modelling). But they’ve continued to extend the ideas they outlined in Culture and the Evolutionary Process, and given rise to a whole school of thought (e.g., Joe Henrich, author of The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter, and now a professor at Harvard, was Robert Boyd’s Ph.D. student at UCLA). A popularized version of their ideas can be found in Not by Genes Alone: How Culture Transformed Human Evolution . The fact of the vitality of this research program is evidenced in part by how cheap copies of Culture and the Evolutionary Process are in comparison to the other two works. I have all three, but the first two I grabbed at used book stores where I stumbled upon them and immediately realized that they were listed far cheaper than they’d be online, because copies are so much rarer.

41CAhu6biSL._SX331_BO1,204,203,200_ If you are interested in the above topic, you should get a hold of at least one of the above books. For those with some background in evolutionary genetics modeling, you’ll feel very comfortable (I recommend Mathematical Models of Social Evolution: A Guide for the Perplexed for an up-to-date take). But today I bring this all up because Peter Turchin has just announced the birth of a new organization, Cultural Evolution Society. In describing the backstory of how this society came about Peter references a visit to Davis in 2014. I happen to have been there, and had good fun with with both Peters (Turchin and Richerson) dining on Korean barbecue and downing red wine. The precis for Ultrasociety was already present in Peter’s mind at that point, but I don’t recall talk about a society for the study of cultural evolution. That may be due to the fact I wasn’t privy to all the conversations, or, that I was rather inebriated soon enough as there was no way I could keep up with Peter Turchin!

I sincerely hope more students interested in evolution will begin to look to cultural processes as well. If you are a human evolutionary geneticist it strikes me as not just something that would be a bonus in terms of insight, but a necessary aspect of the field. For the past generation there has been a emphasis on culture alone, as the co-evolutionary ambitions of Wilson and Lumsden in their original groundbreaking work have been somewhat set to the side. I think that will change in the near future, as many of the thinkers who are pushing the field forward know that at some point cultural evolution and evolutionary genetics will fuse again….

• Category: Science • Tags: Cultural Evolution, Science 
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9780226520438 A very fertile area of evolutionary science is the understanding and modeling of human culture. But it’s hard, which is why my aspiration is to be an evolutionary geneticist in a more classical sense. Not only is it hard, but people don’t appreciate it, because they think they understand “culture.” Robert Boyd and Peter Richerson’s The Origin and Evolution of Cultures is an excellent introduction (with Not by Genes Alone for a more popular audience), but Alex Mesoudi’s Cultural Evolution: How Darwinian Theory Can Explain Human Culture and Synthesize the Social Sciences is a more recent survey which I think is very worthwhile. 0226712842 Complementary to the modelers, who draw from classical genetic frameworks (going back to Cultural Transmission and Evolution by Cavalli-Sforza and Feldman), are the cognitive anthropologists, represented by Dan Sperber and his colleagues (Explaining Culture: A Naturalistic Approach). Another way to look at this is that it is cultural anthropology without the Post-Modern Voodoo. In other words, it strives for disciplinary relevance through a fidelity to reality, rather than political and social impact.

This is all to highly recommend you read an excellent post on cultural evolution, Why Cultural Evolution Is Real (And What It Is). I don’t link to blogs much because it is usually more useful to read the paper, or the book, but in this case I think the writer really reduced the essentials of the field down to a manageable extent. Hopefully it will encourage readers to pursue their own avenues of inquiry.

• Category: Science • Tags: Cultural Evolution 
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9780226520438 There’s a new paper in Science, A network framework of cultural history, which is interesting, and naturally a media splash (it is in Science). The paper illustrates the power of “Big Data” in a domain where most people have not thought to utilize big data. The authors state that “we have reconstructed aggregate intellectual mobility over two millennia through the birth and death locations of more than 150,000 notable individuals.” In the past historical judgments, especially those in the domain of culture, had to be conceded to those with a thick and dense personal database gained through a lifetime of erudition. I’m thinking for example the reduction of a lifetime of scholarship that you can literally feel as you work your way through Jacques Barzun’s magisterial From Dawn to Decadence. But there are serious shortcomings with this sort of intellectual endeavor when it comes to gaining a better grasp of reality. A personal example should suffice. I’ve been thinking of purchasing Alan Cameron’s The Last Pagans of Rome. We don’t need to get into the details, but Cameron basically argues for a major revision for our understanding of the Late Antique transition from paganism to Christianity. This argument is buttressed by the fact that Cameron is one of the world experts, a master of the literature without parallel. The problem is that how exactly do you judge the quality of argument from someone who has a better grasp of the topic than you, perhaps by orders of magnitude? Who are you to disagree if Peter Brown is impressed?

Origin_and_Evolution_dust_jacket_small Some of the same issues outlined by Noam Chomsky in his famous critique of fashionable “deconstructionism” actually applies to elements of humanistic scholarship in practice if not the ideal. In actuality I could learn Latin and Greek and wend my way through the scholarship which Cameron draws upon (I suspect that I would do so more slowly because I lack a strong natural adult fluency with languages, but it is feasible). But in reality very few people have the time to reproduce to the same magnitude the knowledge database of a specialist in a particular area. With the diversity within academia it may even be that a given topic has only a few individuals of parity in terms of expertise. Obviously this causes a problem, because at the end of the day many arguments have to be resolved by appeals to authority. There are some workarounds. For example, one may not have specialized knowledge about a particular area, but in many cases specific instances are likely part of a broader pattern. I’m more liable to give credence to a particular argument if I can check analogous cases in other contexts where I do have thick knowledge, and see that it checks out. If, on the other hand, the argument flies in the face of the general trend I am more skeptical.

downloadBut a better ultimate solution is to quantitize and formalize. This is why the above paper is exciting. The only schematic that I can recall from The Origin of Species is a tree of life, the precursor to the phylogenetic trees which are common today. But it was the cladistic revolution, and later the emergence of computational statistical methods, which have revolutioned phylogenetics and turned it into a reproducible science which does not rely upon specialized domain knowledge. Before World War II if you wanted to know about the systematic relationship of ant genera you would have to consult an expert or a work written by experts. Today you can actually pull some sequence data and construct the tree yourself! That is where we need to be when it comes to a scientific understanding of human culture and history.

Nevertheless there are downsides to this process. In National Geographic Peter Turchin says of this work: “This is a terrific data set, but they are not testing a scientific question here….” If you read the paper, and the press coverage, you see lots of neat visualizations which are representations of the patterns extracted from the data, but to a great extent they are representations of what we already know. Very few non-quantitative scholars would be surprised that eminent individuals tend to move from rural areas to urban ones. Or that Rome and Athens were prominent magnets in 300 AD while London was in 1800 AD. There is value to be gained in formalizing this, to establish an algebra of history if you will. But this is not revolutionary; the field of cliometrics has been around for two generations. What is different is that computational methods can be brought to analyze data far more effectively. But a major temptation of this sort of cutting edge analysis is data dredging, as well as the issues that come with ascertainment bias. For example in National Geographic the first author states:

The distance that people moved over their lifetimes has also changed “very little,” the study says, over the past eight centuries. It grew from a typical distance of 133 miles (214 kilometers) in the 14th century to 237 miles (382 kilometers) today, despite the advent of automobiles and airplanes. Schich expected that the opening of the 3,000-mile (4,828-kilometer) trip to the New World after 1492 would stretch the distance much farther.

“People in the past were not so different from us,” Schich says, noting the records include accounts of Jesuit priests who traveled to China in the 17th century. “It’s very strange to think my odds of moving a long distance are similar,” he says, with a laugh.

This is certainly a result that would surprise many, but please remember that the database is a selection of notable individuals. I would bet that the change would be far greater if you had a sampling of most of the world’s population, rather than ~150,000 extremely notable ones from the last few thousand years. Immanuel Kant aside, those people in the past who became famous often did so by migrating and getting involved in the events of the world, which entailed travel. They were atypical (consider also that every single Roman Emperor was probably functionally literate in a world where this was a minority capacity [the idea that Justin was illiterate is probably a slander]).

To make the best use of the data we need to be clear about our thinking. I do think it goes beyond just asserting that we need hypotheses, though that’s part of it. Genomics is the product of the age of big(ger) data, and it has had to deal with problems of false positives being confused for real signals because old statistical thresholds became out of date. Culturomics has a lot it could learn from the experience of biologists before 2010. With all that said, there is a body of formal theory which can move in and start to operate upon the data set. Boyd and Richersen’s The Origin and Evolution of Cultures and Cavalli-Sforza and Feldman’s Cultural Transmission and Evolution are good places to start. Recently I read Alex Mesoudi’s Cultural Evolution: How Darwinian Theory Can Explain Human Culture and Synthesize the Social Sciences, which is newer, and probably aimed at an audience that is a touch less specialist. I highly recommend it for those interested in this topic (if you have an evolutionary genetics background much of it goes fast because it is review of basic theory).

Let me finish with a quote from The Genetic Basis of Evolutionary Change by Richard Lewontin:

For many years population genetics was an immensely rich and powerful theory with virtually no suitable facts on which to operate. It was like a complex and exquisite machine, designed to process a raw material that one had succeeded in mining. Occasionally some unusually clever or lucky prospecter would come upon a natural outcrop of high-grade ore, and part of the machinery would be started up to prove to its backers that it really would work. But for the most part the machine was left to the engineers, forever tinkering, forever making improvements, in anticipation of the day when it would be called upon to carry out full production….

Apply your regular expression substitution where appropriate.

• Category: History, Science • Tags: Cultural Evolution 
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My daughter has four grandparents. Genetically she is a little over 25 percent her paternal grandfather and maternal grandmother, and a little under 25 percent her maternal grandfather and paternal grandmother.* Why? Because she is 50 percent genetically identical by descent with her mother and likewise with her father. This is all rather straightforward. But what about culturally?

With biological heredity we can speak of genes, the substrate by which inheritance occurs. With culture memes have been far less fruitful as anything more than an illustration, as opposed to the basis of a formal system of logic and analysis. Nevertheless, we can describe with relative clarity many aspects of culture as a trait or phenotype. And this is important. Recall that evolutionary process was characterized by Charles Darwin despite lacking a satisfying theory of inheritance.

One of the more fascinating aspects of surveying human phenotypic variation is that one can consider the differing dynamics which those which are genetically controlled, at least in part, are subject to in contrast to those which are entirely “memetic” in character. Variation in skin color, for example, is mostly genetically controlled. In other words, skin color is a heritable trait in a genetic sense. In contrast the language one speaks is a function of milieu. One’s hair form, blood type, and nose shape, are matters contingent upon one’s biological parents in a necessary and determinative sense. Language, religion, and culinary preferences are accidents contingent upon one’s parents’ preferences.

But it doesn’t end here. In sexual organisms genetic inheritance is symmetric (the autosomal genome has equal contributions from both parents), and exclusively vertical (parents to offspring). In contrast cultural inheritance can be asymmetric (i.e., one inherits by and large the culture of one parent) and horizontal (one inherits the culture of one’s peers). In The Nurture Assumption Judith Rich Harris relates the story of cultural continuity in elite British boarding schools. For generations norms and folkways were transmitted from older students to younger ones, with no parental input. This regular and systematic inter-quasi-generational horizontal transmission illustrates flexibility of cultural transmission which has few parallels in biological genetics. One reason that the logic of biological genetics is powerful is that the system is straight-jacketed by is own constraints, reducing the space of inferences and narrowing one’s extrapolations. Often complexity breeds intractability (see: economics). This is why a formal and systematic study of cultural evolutionary process analogous to that in biology has been a quixotic quest (promoted periodically by individuals of note such as E. O. Wilson and L. L. Cavalli-Sforza, and pushed forward by Peter Richerson and Robert Boyd and their students for several decades).

And yet all this is the broader purview of a paper in Proceedings of the Royal Society B. It is not online as of yet, so I will point you to the report in Nature, Genes mix faster than stories. Here is the top line result:

If folk tales simply spread by diffusion, like ink blots in paper, one would expect to see smooth gradients in these variations as a function of distance. Instead, researchers found that language differences between cultures create significant barriers to that diffusion.

These barriers are stronger than those for the exchange of genes — a message that might be crudely expressed as: “I’ll sleep with you, but I prefer my stories to yours.”

The irony here is that despite the powerful flexibility of cultural transmission, quite often it is cultural variation which exhibits sharp inter-group differences. Both common sense and population genetic theory support this finding. Without inquiring further into the matter I will assert, and be willing to take a $100 bet, that the genetic distance between the Flemish and Walloons of Beligum is smaller than that between the Walloons and Catalans. The language of the Walloons is clearly more closely related to other Romance dialects than that of their Flemish neighbors (go to Google Translate and listen to various Germanic and Romance languages with the same phrase, and it is obvious). But it does not follow that this cultural resemblance must entail a genetic resemblance.

As far as population genetics goes, gene flow is a very powerful force in equilibrating allele frequencies. Only 1 migrant per generation is needed between two populations to prevent them form diverging. Even a 1 percent admixture between two populations will quickly equilibrate allele frequency differences, especially considering that on most loci those differences are not of the disjoint character (frequency 0 vs. 1). Continuous gene flow defined by isolation by distance is a constant homogenizing force across adjacent populations.

But the genetic homogenization on a genome-wide inter-population scale mediated by migration does necessarily hold for culture. It may in some cases, but by and large it does not. This is most easy to illustrate with language, and that is why I focus on that example. The case of the “rape of the Sabine women” by the early Romans is a legendary illustration of the distinction between cultural and genetic inheritance. The Romans assimilated many groups early in their history. In fact, the elite patrician gens Claudia even had paternal Sabine ancestry. But no matter the biological nature of their genealogy the Latin Roman cultural matrix persisted, and propagated. The children of the Sabine women were culturally Roman, not a hybrid between the Sabine and the Roman.

One can illustrate this reality with other cultural characters. Modern Mexicans are a genetically hybrid population between Europeans and Amerindians. But their religion is a European sect (even if their Roman Catholicism has an indigenous flavor, no one would confuse it with the Aztec or Maya religion). Their language is also a European language (even if there are indigenous loan words, regional Mexican Spanish is intelligible with Castilian). But, their cuisine arguably has a predominantly Amerindian basis, albeit inflected with Iberian influences.

The focus on regional, ethnic, and national constructs here is not coincidental. Cultural variation as noted above exhibits high levels of inter-group variation. When comparing the genes of the Yoruba and Tuscans, most of the variation is within each group. But when comparing the language of the Yoruba and Tuscans, most of the variation is across the two groups. The organismic analogy for groups or cohorts of individuals applies much more appropriately to cultural entities than it does to biological genetic abstractions (e.g., the Body of Christ). The origin of the term shibboleth illustrates the functional relevance of this reality of inter-group variation: even though culture is highly plastic across generations and populations, it is not always facultative in the lives of individuals. The way you speak marks your origins and your class. It constraints your norms, and shapes with whom you identify.

And with that, back to my daughter. She will speak English, and she will be irreligious. Her norms and views will not be atypical for the average American. She will eat bacon (OK, she has), and when of age, drink beer. In all ways culturally that matter she resembles her maternal grandparents, and not her paternal grandparents. There was never a great question about this. In choosing to bring up their children to an American milieu my parents risked severing us from the culture in which they were embedded, and which nurtured them. So it is, and so it will always be. The dreams of generations past may die, but their genes live on.

* Her whole recent pedigree has been genotyped, so these proportions are known with precision.

(Republished from Discover/GNXP by permission of author or representative)
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Fascinating paper, Evolution of music by public choice, in PNAS.* The paper is open access, but ScienceNow has a serviceable summary. One somewhat obvious implication from this sort of research, which utilizes human preference to shape a cultural form, is that the topography of human artistic expression is non-arbitrary. In other words, aesthetics is not just historically contingent fiction, but draws upon a deep well of our sense of beauty and pleasure, whether for adaptive or non-adaptive reasons (i.e., culture as byproduct, later subject to functional selection).

But I’m struck by the last section:

The DarwinTunes system can, similarly, be extended to accommodate these additional selective forces by allowing individual consumers to select among variants (i.e., compose) before releasing them into the population or by allowing consumers to see each other’s preferences. The relative importance of selection at these different levels—producer, consumer, and consumer-group—in shaping the evolution of the world’s music is unknown and may vary among societies. Western societies have long had specialist guilds of composers and performers; however, in other cultures, participation is more widespread [e.g., early 20th century Andaman Islanders]. The ability to download, manipulate, and distribute music via social-networking sites has democratized the production of music and may change the balance of these forces again. In partitioning these selective forces, our analysis points the way to the future evolutionary dynamics of digital culture

One of my pet theses is that in many ways modern society is actually a throwback to a more primal condition of human action and interaction. That the thousands of years of agricultural civilization were characterized by cultural kludges which exerted constraint, restraint, and channeled our evolved urges and impulses in a manner which allowed for social stability. With the society of economic surplus individual preference now looms far larger than it did in the near past, and resembles perhaps reconstructs the state of affairs of the far past, though for different reasons. Ancient hunter-gatherers were not adherents of Jeremy Bentham or John Stuart Mill. Rather, in small bands the weight of any given individual opinion naturally would be far larger than in the villages which followed.

Perhaps the baroque and highly textured music of the early modern period was the last great florescence of hierarchical societies which reigned supreme in the great interregnum between Paleolithic antiquity and post-industrial modernity? A world of nearly free music and amateur dispersed production may return to the roots of our species, from the vaulted arches of aristocrats back down the earthier tastes of the commons. Those more culturally aware could comment on the possible democratization of music even before digital technology, as mass consumer culture swept aside classical forms of artistic production and consumption.

Citation: Robert M. MacCallum, Matthias Mauch, Austin Burt, and Armand M. Leroi, Evolution of music by public choice, PNAS 2012, doi:10.1073/pnas.1203182109

* Disclosure: long-time readers will be aware that Armand Leroi, one of the authors listed, is a friendly acquaintance of mine.

(Republished from Discover/GNXP by permission of author or representative)
• Category: Science • Tags: Cultural Evolution, Culture, Music 
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John Winthrop, ~1600. Mitt Romney, 2008 – image credit, Jessica Rinaldi

Recently Megan Mcardle had a post up where she expressed curiosity as to why “futurists” circa 1900 had a tendency not to imagine revolutions in clothing style which might have been anticipated to occur over the next few decades. You also see see this in Star Trek in the 1960s, where faux-future fashion was clearly based on the trends of the day, from the beehive hair to miniskirts. So I thought this comment was of interest:

I don’t know the answer, but I don’t know that they were wrong to do it. Keeping fashions exactly the same as the present generally winds up with more in common with the actual future than deliberate “future” fashions. A fair number of men still wear ties, and on rare occasions a few even wear tailcoats; rather fewer wear silver jumpsuits.

There have been a few counters to extreme fashions in media SF: “Blade Runner”‘s lead wore the same trenchcoat as his noir forebears; “Babylon 5″ went for modified business suits and moderate variations on military uniforms; the “Battlestar Galactica” reimagining was pretty much straight conservative turn-of-the-millennium wear despite being in a far different time. How have those worn versus the approach taken by “Star Trek” or the 2015 segment of the “Back to the Future” movies?

I’m not sure that I accept this case as airtight, but this is certainly true in the specifics. Though I just saw some clips of Running Man for the first time on Youtube, I viewed Blade Runner a few years back for the second time and was struck by how undated it was in regards to fashion sense. At least in a very noticeable manner. It got me to thinking of the nature of cultural evolution even then.

If you read this weblog with any closeness you know that I have a pretty orthodox skepticism of supra-individual level natural selection biologically. By this, I mean that the unit of selection above the level of the individual is often difficult to maintain because of the technical obstacles. To be concrete, consider that the vast majority of genetic variation between two adjacent human demes is to be found within them, not across them. As the power of selection is proportional to the genetic variance which it has to work with that means that lower level selective forces are far more powerful all things equal. All things are not always equal, so that doesn’t render higher level selection impossible, but it does load our die in terms of expectations.

But I think it is somewhat different when it comes to culture. As I said above most of the genetic variation between two spatially adjacent demes is partitioned within them, not across them. So it might be reasonable for allele A to have frequency of 45% in deme 1 and 55% in deme 2. There’s a difference, but you would probably not want to make inferences of a person’s identity in a particular deme by their allelic state.

Now move the toy model to culture. One can easily imagine language A having frequency of 95% in deme 1 and 5% in deme 2. Even accepting that most populations are at a dialect continuum so that this doesn’t mean that much, there will be cases when populations are verging upon another group which speaks a totally unintelligible language. The dialect of Ionia was different from that of Aeolia, but there was a clear and distinct difference between these Greek dialects and the languages of the Thracians. The term “barbarian” derives from the confused incomprehensible babbling of foreigners to Hellenes.

A real life example of the salience of culture and the relative triviality of genetics in selection would be what occurred in Southeastern Europe in the 1990s. The Serbs, Croats, and Bosniaks (Bosnian Muslims) emerged out of the same milieu of South Slavic tribes which pushed into the Balkans in the wake of the collapse of the Byzantine frontier in the 6th century. Their languages are mutually intelligible. But, because of religious differences these three groups have radically different cultural orientations. The Croats are Roman Catholics who face West. The Serbs are Orthodox Christians who turn to Russia. And the Bonsiak identity is a product of the Ottoman period, when a substantial fraction of South Slavs and Albanians converted to Islam but did not assimilate to a Turkish identity.

Massacres all across the former Yugoslavia were perpetrated based on cultural cohesion predicated on these tribal markers and civilizational affinities. The biological difference between these groups was marginal at best. The stark substantive religious difference between Serbs and Croats is far more recent than the original conversion to Christianity by the Western and Eastern Roman churches, because the chasm between what became Roman Catholicism and Eastern Orthodoxy really escalated in the medieval period and later the Ottoman years. As for the Bosniaks, they seem to have emerged out of an environment of marginal South Slavic highlanders within the last five centuries.

The power of culture to be buffeted by natural selection is contingent upon the ability of memes to rapidly homogenize and differentiate through conformity toward alternative norms. Differences once non-existent can quickly harden and seem eternal and inflexible. Biological evolution constrained by the parameters of Mendelian genetic inheritance is by nature somewhat more gradual and less protean.

I’ve been focusing on space, but why restrict it to that? The chart to the left shows what I have in mind: a change in the parameter of space or time when comparing two populations is only relevant if you’re talking about inter-demic competition. In purely descriptive terms they’re probably somewhat interchangeable. Imagine two groups which are basically disjoint on a quantitative cultural trait. I mean that they don’t overlap at all. To give an example, how about the number of times you have to pray per day. Population 1 could hold to a religion which suggests that 10 short prayers has the most merit, while population 2 adheres to a religion which asserts that 3 short prayers has the most merit. If you assume that religion is enforced top-down so that everyone in the population conforms, not anthropologically unrealistic, then one can conceive of a scenario where there are a few deviants, but the distributions don’t really overlap. The two populations occupy different locations, so there’s perfect correlation between cultural form and position in space. But the same can occur with time, as cultural forms evolve.

This is where punctuated equilibrium comes to mind. I’ve gone on the record as thinking this model is overrated. It’s a fine enough descriptor of the fossil record and change on the scale of eons, but I don’t see much mechanistic interest because I believe evolution is mostly scale independent. And yet I wonder if it might be a much more useful description for what happens to cultural forms. There are long periods of stasis and change on the margins, followed by radical breaks from the past. I have read that the standard business attire of elite males in the modern world derives from the suits preferred by Calvinist Northern Europeans. For various reasons I think this is an over simplification, but it seems obvious that phenotypically the modern man of power resembles a Roundhead more than a Cavalier in public. In fact the modern man resembles the 5th century Frank in trousers far more than the 3rd century Gallo-Roman in toga. The substantive distance in a trait value can be far greater over small notionally time periods because of the wild swings in the rate of cultural change.

The observation that the fossil record manifests discontinuities and shifts due to the coarseness of its measure of evolutionary change is interesting, but ultimately I don’t know how actionable it is in follow up projects. It’s a scaffold, not a pathway. But I do think that a better quantitative measure of the nature of cultural change can be very useful, because it can spotlight the “hinges of history.” In the past three generations it seems that the years from 1965-1970 were particularly important in all manner of ways. But is that so? And if it is so, why?

(Republished from Discover/GNXP by permission of author or representative)
• Category: Science • Tags: Cultural Evolution, Culture 
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The fruits of human cooperation

ResearchBlogging.orgThe Pith: Human societies can solve the free rider problem, and generate social structure and complexity at a higher level than that of the band. That implies that much of human prehistory may have been characterized by supra-brand structures.

Why cooperation? Why social complexity? Why the ‘problem’ of altruism? These are issues which bubble up at the intersection of ethology and evolution. They also preoccupy thinkers in the social sciences who address fundamental questions. There are perhaps two major dimensions of the parameter space which are useful to consider here: the nature of the relationship between the cooperators, and the scale of the cooperation. An inclusive fitness framework tracks the relation between altruism and genetic relatedness. Reciprocal altruism and tit-for-tat don’t necessarily focus on the genetic relationship between the agents who exchange in mutually beneficial actions. But, in classical models they do tend to focus on dyadic relationships at a small scale.* That is, they’re methodologically individualistic at heart. So all complexity can be reduced to lower orders of organization. In economics a rational choice model of behavior is individualistic, as are the critiques out of behavioral economics.

There are other models which break out of this individualistic box, insofar as they make analogies between organisms at the individual scale to social entities which are aggregations of individuals (e.g., a colony or ethnic group). The society as an organism has an old intellectual pedigree, and was elaborated in great detail by Émile Durkheim. More recently David Sloan Wilson has attempted to resurrect this framework in an explicitly evolutionary sense. Wilson has also been the most vocal proponent of multi-level selection, which posits that the unit of selection can be above the level of the gene or individual. For example, selection operating upon distinctive ‘demes.’ Roughly, a breeding social unit.

There are major theoretical and practical issues with evaluating social units as ‘organisms.’ I will set those aside for now, and shift the focus to humans. I do so because some of those theoretical and practical issues abate when you put the spotlight on higher order cultural structure and variation. In a more technical sense it seems rather obvious that humans have the ability to throw up a large amount of between group ‘memetic’ variance, and maintain that variance, long enough that selection may be able to operate across the two different phenotypes which are homogeneous within group and utterly disjoint across group.

But even if such ‘cultural group selection’ is possible, that does not negate the power of kin, as well as other ‘lower level’ dynamics which may operate at cross-purposes with organismic social units. The biggest problem which comes to mind is the ‘free rider,’ the individual who takes from the benefits accrued to group harmony, but does not put anything into the system and so incur a cost. Over the long term evaluated on the individual scale the free rider is the fit, and therefore the group will become far less effective as its phenotype and genotype wax. This powerful logic is why individualist dynamics are so much more attractive. By simply optimizing fitness through invariant individual behavior you don’t have to confront the specter of the long term futility of the group strategy in the face of self-interested personal tactics.

Yet if you think about it the same problem confronts conventional biological organisms at the scale of the individual. We’re a coalition of disparate cells, some of which even retain their own distinctive genetic lineage (mitochondria). How is the problem of cooperation at this scale solved? If you want a book-length treatment, get Mark Ridely’s The Cooperative Gene: How Mendel’s Demon Explains the Evolution of Complex Beings. But we do have a variety of tactics to stall the ourselves from self-destructing via intra-organismic competition, though in many cases those tactics are futile by the end of your life. I’m referring here to the high probability that you’ll develop cancers, which are basically individual cells whose selfish replicative propensities destroy the useful equilibrium of tissues which help to maintain the integrity of the individual. Over the short to medium term cancerous lines of cells are highly fit, as they spread throughout your body. But over the long term they are self-defeating, insofar as the organism which they parasitize as free riders eventually comes crashing down due to the weight of the stresses which the selfish cells impose on the complex cooperative edifice that is the individual.

Many of these same dynamics have social applicability. In fact the metaphors at the level of cell and tissue derive from older social concepts. So let’s move back to humans. One extreme model of social complexity posits that all the baroque richness of human societies we see today are ad hoc extrapolations and reconfigurations of impulses and instincts which were shaped in an environment of evolutionary adaptedness (EEA) of the hunter-gatherer band. As an example, the idea of meta-ethnic spiritual brotherhood which is common to many ‘higher religions’ is simply an elaboration on our cognitive disposition to think in terms of kinship due to the evolutionary effect of inclusive fitness. Many individual selectionists, most radically George C. Williams, but also Richard Dawkins, seem to posit that human nature is at base positively evil in its selfish intent. Despite Dawkins’ atheism and anti-Christianity I have wondered on occasion if he didn’t have some similarities to a particular sort of reactionary Roman Catholic who took St. Augustine’s theories of original sin too much to heart. Be as that may be, these sorts of individual models generally either imply that social order and complexity are incidental, if valuable, byproducts of proximate instincts, or, social constructions emerge out of phenomena operating at cross-purposes with the stream of evolution (e.g., a complex ideological system constructed from our general intelligence).

This is of course one end of the spectrum. At the other end are a range of broad families of ideas which are group selectionist, or posit a more complex and nested array of dynamics and forces. Williams and his admirers were certainly right to point out the inchoate and woolly nature of much of the ‘survival of the species’ talk which was in the air in the mid-20th century. And, I think talking of taxon level biological selection is something we should do very cautiously if at all. In other words, I accept the general scale independence of evolution. But I do not believe that the 50,000 year experiment of human beings with social complexity is one long extended spandrel. Assuming infinite time for the human experiment to work itself out I can accept that social complexity is due to collapse because of its internal contradictions, but I am but a man alloted a mere few score years, and tend to assent to the proposition that phenomena which span millennia have some right to be accorded the due respect given to the ‘permanent things.’

A new paper in PNAS looks at a society of people who operate in the gray land between ‘small-scale hunter-gatherer bands’ and national entities with all the institutional accoutrements which that entails. The focus of the study are he Turkana. They are a group of Nilotic pastoralists who number between 500,000 and 1 million. They are subdivided into smaller patrilineal units, as well as territorial sections. But the major organizing force among the Turkana in terms of collective action seems to be ‘age group’ cohorts. Basically these are groups of men who come up together as peers. It seems that the Turkana lack institutional religion or formal hereditary leadership. So no kings or warlords of the Turkana who pass their charisma on to the next generation. And the Turkana fight. Or more precisely they raid. As pastoralists they raid for cattle, and they raid for vengeance. Finally, it seems that they do not as a rule raid each other, but rather direct their martial energies outward upon other ethnic groups.

Here’s the abstract, Punishment sustains large-scale cooperation in prestate warfare:

Understanding cooperation and punishment in small-scale societies is crucial for explaining the origins of human cooperation. We studied warfare among the Turkana, a politically uncentralized, egalitarian, nomadic pastoral society in East Africa. Based on a representative sample of 88 recent raids, we show that the Turkana sustain costly cooperation in combat at a remarkably large scale, at least in part, through punishment of free-riders. Raiding parties comprised several hundred warriors and participants are not kin or day-to-day interactants. Warriors incur substantial risk of death and produce collective benefits. Cowardice and desertions occur, and are punished by community-imposed sanctions, including collective corporal punishment and fines. Furthermore, Turkana norms governing warfare benefit the ethnolinguistic group, a population of a half-million people, at the expense of smaller social groupings. These results challenge current views that punishment is unimportant in small-scale societies and that human cooperation evolved in small groups of kin and familiar individuals. Instead, these results suggest that cooperation at the larger scale of ethnolinguistic units enforced by third-party sanctions could have a deep evolutionary history in the human species.

The raw numbers killed proportionally are rather high, but not atypical for many pre-state societies. There are two types of raids. Offensive mass attacks, which seem to be the closest the Turkana and their rivals come to “pitched battle,” and stealth raids with smaller complements of men. I couldn’t but help think of the Cattle Raid of Cooley. Material benefits are real and tangible in many cases, 3 cows per man if victory is theirs. But the costs are real too, the mortality rate is on the order of ~1% per raid. This explains how nearly ~20% of men are dying in their prime years due to violence. Assuming independent probabilities of death you only need 20 raids to have an expected outcome of survival of 0.80. Also, it must be noted that some raids are purely retaliatory and don’t entail any loot, or benefit, to the fighter. These raids of vengeance maintain the honor of the Turkana, and serve as deterrents to future attacks from their enemies. Mass action “tit-for-tat” if you will.

With all the costs and benefits as they are there is naturally free riding. Men beg off on fighting because they can’t find someone to watch their herds, or they’re ill. This might be especially tempting on vengeance raids, where the benefit is a public good which isn’t privately dispersed. Some men avoid being at the tip of the offensive spear during the conflict, and let others take risks so they might live another day. And of course there are stragglers who deviously catch the fleeing cattle first, and secure the best or only portions. If you’ve tread epic myths you know all the varieties of cowardly trickster behavior which might manifest when you are faced with temptations. These raiding parties are numerous, on the order of 250-300 men. They don’t consist of men who are closely related and from the same kin group, but rather a heterogeneous local lot of Turkana, albeit clustered by age group. It seems that the median number of age groups, settlements, and territorial sections, represented in these war parties are around 5 for all of these variables. These war parties are above Dunbar’s number, are not part of some unified group aside from ethnicity and local proximity.

Theory predicts that when you have a diverse lot that diverse interests are going to result in temptation to cheat and let those with whom you’re not close take the fall. How is the problem solved? I’ll quote:

Informally enforced norms allow the Turkana to partially solve the collective action problem in warfare. In 47% of the force raids in which desertions were reported, at least one of the deserters was sanctioned, and in 67% of the force raids in which cowardice was reported, at least one of the cowards was sanctioned (Fig. 7). There are two levels of sanctions. When a warrior’s behavior in a raid deviates from that of his comrades, he is subjected to informal verbal sanctions by his age-mates, women, and seniors. If there is consensus in the community that the act merits more serious sanctions, corporal punishment is initiated. Corporal punishment is severe: the coward or deserter is tied to a tree and beaten by his age-mates. One participant had scars on his torso from being whipped by his age group more than a decade earlier.

This is rather straightforward. In early modern European armies which were involved in set-piece battles there were dragoons stationed at the rear whose role was discourage desertion and retreat through intimidation and force. Obviously the incentive structure here was somewhat different, as defeat in war for a nation-state can have drastic consequences and punishment after the fact may be rendered moot. In the case of these raids documented in this paper it does not seem that the Turkana were involved in existential genocidal conflicts. This may be a function in part of modern norms and the constraining effect of African nation-states in which they’re embedded. Battles between regional warlords in late medieval Europe still occurred, and the monopoly of force accrued to the central government and the monarchy only over time. I would not be surprised if Turkana norms have shifted concomitantly, and non-capital punishment after the raid is an adjustment to the lack of existential urgency in this conflicts.

We know all of the results in this paper in the general verbal sense. How do you fix a free rider problem? You punish them! But the devil is in the details. Here the authors show quantitatively and descriptively that group level dynamics can manifest in a pre-state society above the level of the family band. In fact the unit of organization, the ethno-tribal group, scales up to 500,000 individuals or more! So the social norms were enforced across and beyond kinship groups. Rather it seems that among the Turkana the age groups have a particular power below the level of ethnicity. Presumably what in other contexts might be termed ‘fictive brothers.’ Interestingly these raiding parties were organized and led in an ad hoc and “crowd-sourced” fashion. They illustrate the power of spontaneous dynamics of structured order coming out of a less elaborated and simple social context. And importantly, the violence was directed outward. The rates of murder amongst the Turkana is rather low. Rather, the high risk of death is due to inter-group conflict.

But it seems that the authors are not presenting a simple inter-demic group selection argument. Much of the “action” here operates underneath the level of the group, insofar as group action and cohesiveness is mediated through the regulation of norms of collections of individuals and sub-group entities. This is why I personally find the “group” vs. “individual” dichotomy less than useful. Where do we draw the line from highly elaborated cultural structures built upon atomic units of individual human action to quasi-organismic societies? To a greater extent it seems a matter of taste and convenience, not substance.

One study on the Turkana proves nothing. It may just be part of the bigger puzzle though. For a generation evolutionary psychologists have focused on the model of the hunter-gatherer band during the Pleistocene. Anthropologists working within this tradition have attempted to show that successful hunters and warriors are fecund hunters and warriors. Individual level dynamics then would be validated, as social status is converted into biological currency. From what I have read in the literature (and mind you, I began one theoretically high committed to this hypothesis) the results have been somewhat mixed. This tells us perhaps that one dynamic to explain it all is not going to do the job.

Most of the world’s societies were and are not patrilineal pastoralists. But the Turkana are human, and so they give us a window into the intersection of human psychology and social context, and what that may produce. The intersection is multi-layered, and the product is difficult to distill down to a few broad characterizations. Human social complexity’s raw variety defies broadness of characterization with any economy. But it exists, and it needs explaining, bit by bit.

Citation: Sarah Mathew, & Robert Boyd (2011). Punishment sustains large-scale cooperation in prestate warfare PNAS : 10.1073/pnas.1105604108

* In theory inclusive fitness can obviously be generalized very broadly

Image credit: Wikimedia

(Republished from Discover/GNXP by permission of author or representative)
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Fascinating post by Bayes, Phylogenetics, cultural evolution and horizontal transmission:

For some time now, evolutionary biologists have used phylogenetics. It is a well-established, powerful set of tools that allow us to test evolutionary hypotheses. More recently, however, these methods are being imported to analyse linguistic and cultural phenomena. For instance, the use of phylogenetics has led to observations that languages evolve in punctuational bursts, explored the role of population movements, and investigated the descent of Acheulean handaxes. I’ve followed the developments in linguistics with particular interest; after all, tracing the ephemeral nature of language is a daunting task. The first obvious road block is that prior to the invention of writing, the uptake of which is limited in geography and history, language leaves no archaeological record for linguists to examine. One particular note I’d like to make is that when Charles Darwin first formulated his theory of natural selection, he took inspiration from linguistic family trees as the basis for his sketch on the evolutionary tree of life. So it seems rather appropriate that phylogenetic approaches are now being used to inform our knowledge regarding linguistic evolution.

Like many other attempts applying evolutionary thinking in culture, phylogenetic approaches are, at times, met with contempt. This stems from assertions that cultural evolution and biological evolution differ greatly in regards to the relative importance of horizontal transmission….

I guess the general points to take away from this post are: 1) Do not necessarily assume horizontal transmission is dominant in shaping culture; and, 2) Even with certain levels of reticulation, it does not necessarily invalidate a phylogenetic approach in investigating cultural and linguistic evolution.

I think the point that horizontal transmission may be less important relative to vertical transmission than we’d previously thought in regards to the spread and diffusion of cultures may explain some of the recent findings from DNA extractions which suggest that hunter-gatherers were replaced in Europe by farmers. The standard model before the recent wave of extractions was that farming spread through cultural diffusion, with a minority view championed by L. L. Cavalli-Sforza of “demic diffusion” whereby demographic growth from the point of origination spread a culture, though the initial distinctive genetic signal became progressively weaker through dilution via admixture. But if cultural practices such as agriculture were much more vertically transmitted, from parent to child, rather than horizontally across societies, the genetic pattern of replacement becomes more comprehensible.

Of course, the main caveat is that intermarriage has been very common between neighboring groups. The rape of the Sabine women may reflect a common practice on the part of migratory males; the Greek colonization of the western Mediterranean was almost all male, so the subsequent generations were biologically the products of Greek men and native women (though culturally they were fully Greek, as evidenced by the term “Magna Graecia” to refer to Sicily and southern Italy). It is not atypical for vertical transmission of culture to occur from one parent, and in particular one sex. More recently the descendants of the pairings of Iberian men and indigenous women in Latin America tend to speak Spanish and avow the Christian faith. Though aspects of local identity, such as cuisine and clothing, may retain an indigenous stamp it is no coincidence that these populations are labelled “Latin American” despite their mixed genetic provenance.

Note: In the United States children have traditionally been more often raised in the denomination of their mother than father, so there isn’t always a male-bias in vertical transmission when the parents are not concordant for a cultural trait.

(Republished from Discover/GNXP by permission of author or representative)
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