Razib Khan One-stop-shopping for all of my content

December 21, 2011

The arc of primate social evolution

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….

June 14, 2011

Band of brothers at war

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 ...

February 8, 2011

The Imitation Factor: Evolution Beyond The Gene

Link to review: The wisdom of Seinfeld.

The Imitation Factor: Evolution Beyond The Gene

Link to review: The wisdom of Seinfeld.

January 5, 2011

Kissing & the science of humanity

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.

March 17, 2010

Monkeys are more complicated than you’d think

Filed under: anthropology,Behavior,Ethology — Razib @ 10:39 pm

Generous Leaders and Selfish Underdogs: Pro-Sociality in Despotic Macaques:

Actively granting food to a companion is called pro-social behavior and is considered to be part of altruism. Recent findings show that some non-human primates behave pro-socially. However, pro-social behavior is not expected in despotic species, since the steep dominance hierarchy will hamper pro-sociality. We show that some despotic long-tailed macaques do grant others access to food. Moreover, their dominance hierarchy determines pro-social behavior in an unexpected way: high-ranking individuals grant, while low-ranking individuals withhold their partner access to food. Surprisingly, pro-social behavior is not used by subordinates to obtain benefits from dominants, but by dominants to emphasize their dominance position. Hence, Machiavellian macaques rule not through “fear above love”, but through “be feared when needed and loved when possible”.

Probably would be nicer to have more dots on the scatterplot…but that would involve tracking more troops. Someone needs to pay for more ethologists!

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