Why we still wear pants

Peter Turchin recently published a series of blogs (part 1 and part 2) addressing the question of why westerners wear pants.  It's a story I'd heard before years ago in a comparative Indo-European studies course, but not from an expressly evolutionary perspective and not with Peter's flare.  It's a good story, particularly for introducing cultural evolution, and I don't want to spoil it for those who haven't heard it before.  Nevertheless, not much about this post will make sense if I don't at least mention that wearing pants came about whenever riding horses became an important part of warfare.

As much as I like the story, I made what I thought was a somewhat innocuous comment saying that I would like to see a follow up series of blogs that explored why we still wear pants.  After all, very few people ride horses and, aside from some special exceptions, horse cavalry became obsolete in World War 1.  However, not only has the wearing of pants continued, it has spread, both to societies we've come into contact with and to women within our own society.  This spread has happened without any obvious adaptive advantage.  Moreover, this persistence and spread has occurred despite available alternatives and social movements, such as the androgynous movement of the 1980s, that attempted, and failed, to change these established practices.

Peter's response to this question, while not exactly surprising, was surprisingly dismissive.  His position is that there is no need to explain when cultural traits fail to change.  For him, the lack of change is the null hypothesis.  In his own words:

The null model is dp/dt = 0, where p is the frequency of the trait, and dp/dt it’s (sic) rate of change. If there is change, then dp/dt = c, or dp/dt = cp, depending on the details of how the trait changes. In any case, the greater the rate parameter, c, the faster the trait will change. So if c is high enough you will have yearly changes of fashion, if c is small enough, then it will take decades or even centuries.

The failure of something to change, in Peter's view as I understand it, can simply be dismissed as normal inheritance.  In the absence of variation and/or in the absence of selection pressure to change, we simply go on as we've always done.

I object to this position on a number of fronts.  To begin, it appears to be an assumption, not an empirically established fact.  Moreover, all these equations really establish is that some traits change faster than others, hardly a startling revelation.  What they fail utterly to do is account for why some traits change faster than others.  The salient question, for me, is why dp/dt should ever be zero, or even near zero. 

It is, of course, entirely plausible that Peter is right, that the failure of this particular trait to change might be due to simple inertial processes.  However, this is far from the only possibility.  We need only look to biological systems to see why this is so.  Robustness, the propensity of a system to continue functioning in the face of perturbation, is a general property of complex, evolved systems.  The structure of DNA and the genetic code are robust to mutations.  Proteins similarly tend to perform their functions even with amino acid substitutions.  This robustness is evident all the way up the hierarchy of biological complexity.  Even developmental systems are robust to changes in metabolic pathways. 

I see no logical reason to assume this general property of biological systems, a property that is an adaptation in its own right, should somehow no longer hold true once the level of complexity moves outside the skin of the individual organism.  Moreover, if evolutionary approaches to understanding human culture are to meet their full potential, they must grapple with practical problems in the current world, many of which represent historical patterns from which groups seem almost incapable of escaping.  For instance, Nisbett andCohen have traced modern rates of male violence in the southern United States to Celtic herding cultures, an ancestral pattern that has persisted long after herding faded out as a way of life.  Similarly, Robert Putnam has traced failures of democratic institutions in southern Italy to patterns of social capital building that go back 500 years.

Treating the persistence of these problems as nothing more than null hypotheses drastically reduces the chances of finding real solutions.  Aside from blinding ourselves to the root causes of recalcitrance, robustness paradoxically makes evolvability possible.  A handful of textbook examples notwithstanding, it is rare for a single mutation in biological systems to be adaptive.  Most often, adaptations arise from a series of mutations.  Fragile systems, however, are relatively incapable of building pools of useful variation since any slight change is likely to lead to suboptimal performance.  Robust systems, by contrast, tend to build up pools of variation, some combination of which may prove adaptive when new niches present themselves or existing environmental conditions change.

As for the question that ultimately motivated this post, I have no idea why we are still wearing pants.  If I were to hazard a guess, I would say that once pants became associated with warrior castes they acquired protection by virtue of prestige bias.  This in itself, though, might not have been enough to ensure the practice persisted.  More likely, the wearing of pants started to get tied to concepts in addition to warrior attire.  For instance, pants became associated with markers of gender identity, group heritage, etc.  In other words, it became connected to many other cultural constructs in intricate webs not unlike the way genes often have pleiotropic effects in gene networks.  If so, then wearing pants could become difficult to change even if there were compelling reasons to do so.

Sure, this is all purely conjecture at this point.  However, it hopefully goes some ways toward demonstrating that lack of change is a worthy subject for evolutionary study.

Ultimate Sacred Postulates

I was finishing up Malley's How the Bible Works last night and came across this interesting idea, one that is congruent with some thoughts I had a few years back but never really followed up on:

In Rappaport's model, the most fundamental premises of a society are its "ultimate sacred postulates" (USPs).  USPs are distinguished from the other understandings present in a society in that USPs are nonempirical, beyond the reach of logical refutation, and regarded as unquestionable.  Examples of USPs given by Rappaport are the Shema of Judaism and the Shahada of Islam.  Such postulates have an important social function in that they define a community and thus serve as a kind of core around which the community can transform and adapt to circumstances while preserving its essential identity.  It is important for this function that they be neither empirically nor logically falsifiable, because this shelters them from every having to change.  Their nonempirical, often nearly tautologous nature makes them ideal foundations for community identity.  (pp. 137-138)

This passage brings together a number of strands of scholarship without referring to any of them.  For instance, it is resonant with my own interests in cultural robustness and evolvability.  Note in particular how an instance of robustness, the unchanging nature of USPs, is said here to form a core around which a community can adapt.  In other words, the presence of USPs allow a degree of evolvability by virtue of the fact that they can remain constant markers of group identity.  Presumably, if group identity were not so robust, then the social boundaries of that community might have to be renegotiated with every adaptive change, thus risking group cohesion at every twist and turn of a community's evolutionary trajectory.  The proximate mechanisms by which this robust trait is brought about is by placing USPs outside the realm of refutation, a very clever trick when you stop to think about it.

And, of course, this passage evokes, though likely unintentionally, Lin Ostrom's work.  Clear social boundaries are part of the very first design principle.  This naturally leads me to wonder if USPs might also accompany other design principles as well.  My work on religion and natural resource management doesn't currently touch on this question, but it wouldn't take much effort to launch a study of USPs and design principles from this project.  That isn't to say it wouldn't take a lot more work.  We'd basically have to code each instance we've found of religion playing a role in a design principle for whether a USP is evoked or not.  This might require more research into the specific beliefs involved than what we currently have in the database.  However, it might not if we could get by ignoring the requirement that USPs be "regarded as unquestionable" and instead focus exclusively on whether they are "beyond the reach of logical refutation."  For instance, I would be inclined to code the belief that ancestors are watching over a sacred grove as something beyond the reach of logical refutation.  This point could be argued, but it wouldn't be a bad first approximation, and one we could use our existing coding of case studies to address.

Needless to say, Rappaport has moved to the top of my reading list...

I was going to start a new blog entry for this last quotation from Malley, but it seems closely related to these ideas so I'll just continue here.  Malley makes the point that an important aspect of Evangelical Biblicism is the fact that the canonical texts are closed and well defined, making them clearly demarcated from other kinds of texts.  He then goes on to say:

This conventional boundary affords a different kind of flexibility.  By demarcating the boundary of scriptures very clearly, the content of the texts can be left unspecified.  So long as evangelicals can know what counts as a biblical text, they do not need to have a very elaborate knowledge of what is in those texts.  Their practice turns on establishing links between their ideas and some biblical text or other, and this can be done in ad hoc ways so long as one has some way of knowing what counts as a biblical text.  The closure of the canon affords openness in interpretation.  (pp. 150-151)

So once again we see an example in which robustness, in this case the rigidness of canonical boundaries, can lead to greater evolvability in the form of openness of interpretation.  Good stuff!

Caught Between Scylla and Charybdis

It's been many years since I've seen the names Scylla and Charybdis.  In fact, the last time I read those names was probably in middle school when I had something of an obsession for Greek mythology.  With so many years elapsed, I had to refer to Wikipedia just to be sure I remembered them correctly and, though the details had largely vanished from my mind, I did still retain the basic idea.  Scylla and Charybdis were two sea monsters situated on opposite sides of a narrow straight.  Sailors making a wide berth to avoid Scylla, a six headed beast, ran the risk of coming too close to Charybdis, a formerly beautiful daughter of Poseidon who became a hideous bladder that sucked in and spit out water in the ocean to form whirlpools.  Being caught between Scylla and Charybdis, then, is to be caught between a rock and a hard place, but with ghoulish monsters to make things more interesting.

So what brought these images back to my mind?  They were used as a metaphor in Brian Malley's How the Bible Works to describe the tension Evangelicals face when transmitting their interpretive tradition:

The interpretive tradition is perennially caught between the Scylla of interpretive freedom and the Charybdis of irrelevance:  to much hermeneutic freedom and the tradition disintegrates, loosing its epistemological appeal; too little interpretive freedom and the Bible becomes merely an irrelevant historical artifact, rather than the ever living word of God. (p. 124)

This is relevant not only to our collective work on tight vs. loose congregations but also to my own work on cultural robustness and evolvability.  On the latter point, I find Malley's observations particularly illuminating and worthy of further research at some point down the road.  According to him, the interpretive tradition received by lay people is relatively devoid of interpretive freedom.  People aren't really reading the Bible to search for new meaning.  Rather, they read the Bible in the search for relevance.  They do become skilled in finding Biblical passages that confirm beliefs they hold, but in terms of their personal reading of the Bible, they mostly seek to find ways in which what they are reading can speak to their lives at the moment.  When they find this kind of relevance, they perceive it to be God speaking to them through the intervening text.  Note that this is a very different relationship with a sacred text than what is common in, say, Jewish tradition in which each generation is encouraged to wrestle with the Torah and Talmud in order to create new meaning that speaks to an evolving world.

So where, then, is the source for new interpretations in Evangelical traditions?  How do they avoid the Charybdis of irrelevance?  Malley locates at least a partial answer to this question in Evangelical seminaries.  Ministers often undergo extensive training at institutions of higher education in which a true hermeneutic tradition is taught.  New generations of pastors, then, have the opportunity to read the sacred text anew and engage in a Biblical scholarship that can open up new possibilities.  Obviously, this is a relatively conservative process, constrained as it is by notions of what the previous generation of scholars, who are the current professors, deem acceptable deviance from the norms.  Nevertheless, it is a fertile ground for at least some innovation and this, then, after undergoing its own kinds of selection processes, can leak its way into the more general population of believers, who will generally accept it without much critical thought.  This dynamic strikes me as an excellent example of robustness and evolvability at work.