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A new paper in Nature, Stepwise evolution of stable sociality in primates, was written up in The New York Times with the provocative title, Genes Play Major Role in Primate Social Behavior, Study Finds. As noted in Joan Silk’s article on the paper it should really be phylogenetics play major role in primate social behavior. The model outlined in the paper indicates that phylogenetic relationships between major primate clades is a much better predictor of social organization and structure than simple adaptation to a specific environment, or a linear increase in social organization (group size) over time. Both of these latter dynamics would also be driven by genetic changes, and therefore tie “genes” to social behavior. In other words, genes always matter, it’s just how they matter that differs. Here’s the section of the abstract of the paper of major interest:

… Here we present a model of primate social evolution, whereby sociality progresses from solitary foraging individuals directly to large multi-male/multi-female aggregations (approximately 52 million years (Myr) ago), with pair-living (approximately 16 Myr ago) or single-male harem systems (approximately 16 Myr ago) derivative from this second stage. This model fits the data significantly better than the two widely accepted alternatives (an unstructured model implied by the socioecological hypothesis or a model that allows linear stepwise changes in social complexity through time). We also find strong support for the co-evolution of social living with a change from nocturnal to diurnal activity patterns, but not with sex-biased dispersal….

I read the “letter,” but the reality is that this is one of those papers where you have to read the supplements to get a real sense of what is going on. I haven’t as of this moment, though I invite readers to browse through them and get back with their own assessment of the model. Broadly, I don’t object to the inference generated here…but I do wonder if the transition between the human-chimp ancestor and later hominins is to some extent sui generis. I have suggested that modern humans were “inevitable” after ~2 million years before the present, but I don’t think there was anything inevitable before that period. The overall point of the paper is that history and contingency matter a great deal, which to me implies that we should be cautious about making specific judgments of positions along the phylogenetic tree derived from what we gather from the whole….

(Republished from Discover/GNXP by permission of author or representative)
 
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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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I approached Sheril Kirshenbaum’s The Science of Kissing: What Our Lips Are Telling Us with some trepidation and excitement. The former is a consequence of my hypochondria and its associated germophobia. I have no aversion to kissing in my own life (apologies for divulging personal information), but I did have some worries about having to read about other humans engaged in such an act of hygienic daring. And yet I was excited because I am interested in multidisciplinary explorations of human behavior. And of course I was familiar with the author’s oeuvre, and was expecting an engaging and wide-ranging exploration of the topic at hand.

I was not disappointed. The Science of Kissing is an intellectual full-court press; every conceivable discipline of relevance is brought into the mix. History, ethnography, ethology, neuroscience, evolutionary biology, physiology, and epidemiology, all receive attention, to name just a few of the more prominent lenses which the author fits over the course of the narrative. In other words you’re presented with an intellectual buffet. A well rounded meal will require you to sample widely, but if the lack of punctiliousness of Romans in matters of hygiene is not to your taste, you may find a discussion of the latest neuroimaging techniques and their application to matters of behavioral response more to your liking.


After the first chapter one immediately perceives that The Science of Kissing is not a tight and narrowly argued case for a positive hypothesis. Rather, it is more synoptic. Of broad scope, and yet rather tentative in its conclusions. The author makes clear in The Science of Kissing that this stance of humility of what we know is the position which is warranted by the science as it is now: the science of kissing is immature at best. In fact, this reality seems to have been one of the prods for the author’s project. Her own curiosity as to the lack of a general and accessible entry into the literature, provisional as it is, turned into the opportunity to transform her own journey of discovery into a book-length exposition.

Each chapter in The Science of Kissing is rather concise, but they are bracketed into three thematic portions. First, there is an exploration of the ultimate roots of kissing. That is, why? Naturally this entails a historical perspective, both human and natural. This is where the author immediately abdicates any pretense at making a forceful and tight argument which brooks no ambiguity or uncertainty. A book about the science of kissing might plausibly begin by asserting that the phenomenon is a human universal. No, not exactly. The author reviews a diverse range of contemporary and ancient ethnographic reports which indicate a wide variety of cultural attitudes toward kissing and its substitutes.They are often amusing, and it must be said, occasionally kinky. I have admit that the idea of foreplay not including kissing struck me as profoundly alien, but it was a reality check on the presuppositions that we bring to expectations of the plausible range of human behaviors. On the other hand, the deviations from kissing do seem to share general features with the behavior, whether it be an attention to the face or violation of norms of personal space. For example many substitutes for kissing seem to involve a sort of sniffing of the other, and it could be argued that kissing is one particular route to this general behavior of olfactory exchange. It is also notable that kissing can be found among other animals, for example the Bonobo chimpanzee.

As a social species there are a clear range of ultimate rationales for why kissing may emerge. A form of grooming, interpersonal communication, as well as ascertainment of genetic fitness. But as a complex behavior which is culturally modified and channelled the sum of human and natural historical evidence point to kissing as being a specific instantiation of a general phenomenon. Kissing seems to be on the way to becoming a human universal, but that may be a contingent fact of human history. In particular, the rise of European hegemony, and the acceptability of kissing in companionate relationships within this culture (though not exclusively within this culture, as evidenced by records of kissing in the Hebrew Bible and Hindu epics). But the contingency of the phenomenon of kissing does not entail that its emergence was arbitrary. Rather, the balance of evidence seems to suggest that kissing is a phenomenon which we humans are mildly disposed toward. Kissing exists in related taxa and has been independently practiced across disparate human societies. Ultimately kissing as a universal human phenomenon may not have been inevitable, but it was at least not improbable.

Next The Science of Kissing moves to the proximate: how the phenomenon expresses in a concrete sense. Here’s a chestnut of wisdom: men like sloppy kisses, while women do not. Another: men are much more likely to be willing to have sex with someone without kissing. The author was skeptical about the robustness of such results indicating strong sex differences, and so she decided to do a personal survey. To her surprise these sorts of sex differences were perfectly replicated in her own sample. This is where ultimate causes loom large: males and females have somewhat different sample spaces of possible reproductive strategies as a function of the number of offspring they may have. Women have about ~30 gestations available in their lives. Men on the other hand have a much higher upper bound on the number of offspring they can have via polygyny thanks to the surfeit of sperm. This tension is at the heart of much of evolutionary psychology, so the leveraging of this framework to explain sex differences in kissing seems to be on relatively solid ground.

But the differences between men and women are explored in more than just ultimate abstract causes. The Science of Kissing also delves into behavioral and cognitive neuroscience and genetics, exploring the possible links between chemistry and kissing. Earlier I noted that kissing may serve as a predictor of genetic fitness or compatibility. How? It may be an avenue by which potential mates can assess their long term compatibility, whether through pheromones, or modulation of hormones such as testosterone, oxytocin or epinephrine. Kissing in this telling may be one of the roads which leads to the Rome of pair bonding. This dovetails well with the model where kissing is one of a set of probable behavioral phenomena to facilitate necessary relations for reproductive fitness. The author is admittedly on tendentious ground in this section, but though many of the hypotheses may be falsified, it seems unlikely that all will be.

And then we move to “cooties.” Needless to say this was the chapter which discomfited me the most. And yet the lessons here are rather plain and straightforward. Follow your dentist’s advice. Those of you engaged in promiscuous polyamory may have to worry a bit more than those of us who are not so engaged. And that vampire fad? Don’t get too into biting fetishes unless you want to risk your mortality. Don’t French kiss wild animals. Seriously.

The final in depth section is perhaps one of the more peculiar, and praiseworthy, aspects of The Science of Kissing. Quite often popular science books are written by scientists who focus on their own research, scaffolded with extraneous “hooks” when necessary. If not, they are written by journalists who serve as tour guides to the world of science. Intellectual voyeurs. The author was not reviewing her own research, but she also deviated from the “outsider” viewer as well. She managed to obtain the collaboration of David Poeppel at NYU to perform a set of experiments utilizing magnetoencephalography (MEG). I won’t detail the experiments and their results, except to relay that the author had some “interesting” adventures with finding images of same sex kissing on Google Images. The Science of Kissing begins as a readable but rather conventional popular science book, if a touch on the cautious side. But through this survey of a real set of experiments inspired by the author’s curiosity in researching The Science of Kissing you get a taste of the excitement and possibilities of science as an enterprise and method, rather than a set of results and “facts.” To me this portion seems almost a challenge to the complacent preconceptions of the public as to what science is, as opposed to how science operates. Instead of an answer one is left with a series of questions.

The Science of Kissing tells its story with economy. The chapters are short and to the point. But quite often there is a density of fact which will satisfy. The qualified and nuanced take on many of the issues will appeal to the nerd, who yearns to dig between the layers of the scholarly strata. Quite often I found myself putting the book down to do further research on Wikipedia or Google Scholar. This is not a book which punches you in the face with a bold and explosive thesis. When it comes to human behavior and biology robust bold explosions are hard to come by, so I believe that this tack was the honest one. The author navigates deftly between the shoals of the “blank slate” model dominated by nearly arbitrary historical contingency and a naive genetic determinism which is hard to justify based on the empirical data.

In some ways kissing is something which has two faces. On the one hand most people would not deny its central integrity to our most personal relationships. It seems far more substantive a matter than whether you shake someone’s hand. And yet kissing may also seem a sliver of a window upon the broad expanse which is human nature. The Science of Kissing illustrates that this is not so; an exploration of the phenomenon of kissing allowed the author to shine a bright light on the gamut of the human sciences, from those which focus on the ultimate biological bases of behavior, to those which characterize its proximate manifestations. Perhaps it is the omnipresent and most personal of behaviors which may serve as the most representative windows upon how our biological inheritance interfaces with the environment in which we express our predispositions and needs. How about the science of laughing? Crying? Blinking? The possibilities are endless. But this was an excellent start.

Note: Also follow the author’s posts on the book.

(Republished from Discover/GNXP by permission of author or representative)
 
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This is fascinating. De novo establishment of wild-type song culture in the zebra finch. See ScienceDaily, Birds Raised In Complete Isolation Evolve ‘Normal’ Species Song Over Generations.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Ethology, Genetics 
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Razib Khan
About Razib Khan

"I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. If you want to know more, see the links at http://www.razib.com"