Evolved, adaptive systems are generally robust. In other words, they typically continue to
function even in the face of perturbations.
That is not to say that they are infinitely malleable or that they are
unaffected by changing conditions.
Indeed, they can and do collapse in the face of enough pressure. Nevertheless, as reviewed extensively by
Andreas Wagner (1), evolved biological systems tend to be highly
resilient. For instance, Wagner argues
that the genetic code did not arise by chance, but rather because it is robust
to replication errors. The redundancy in
the genetic code is such that the most common replication errors result in
silent mutations. The arrangement of the
code means that even when replication errors lead to non-silent mutations, they
most often lead to substitutions of amino acids with similar properties. Wagner systematically extends the notion of
robustness to ever higher levels of biological complexity, ending with a
detailed discussion about the ways in which the developmental pathways that
lead to phenotypic traits are robust to variations in the genes that make up
those pathways. My work suggests that
the notion of robustness should be extended even further to include cultural
systems, a subject that has largely escaped the attention of those studying
cultural evolution.
Robustness is an important concept because it illustrates
the ways in which evolution is constrained.
Sometimes, these constraints are imposed by the environment as in the
case of stabilizing selection maintaining local maxima in the fitness landscape
(2). Other constraints are intrinsic to
organisms. Pleiotropy, for example,
constrains evolution because genes may have effects on multiple
characters. A mutation that might be
adaptive for one of these traits may have negative consequences for others
(3-5). Similarly, canalization works to
minimize phenotypic variation in the face of changing developmental conditions
or in the background of genetic variation (6-8). Because many traits evolve more or less
independently of one another, evolutionary constraints manifest at even higher
levels of organization than the organism.
For instance, pentadactyl limbs are retained in organisms as diverse as
humans, bats and amphibians even though these limbs are put to very different
uses and despite the fact that so many other characters have diverged radically
among these species. It seems that once
certain evolutionary trajectories have been launched, variation becomes limited
to paths of least resistance and that novelty can only emerge in certain
directions (9). This may account for why
some body plans persist for hundreds of millions of years. Although the traditional location of most
modern body plans within the Cambrian explosion has been called into question
(10), none of the theoretical objections cast doubt on ancient origins and
persistence of phyletic traits.
Robustness is also an essential concept for understanding
evolvability, the ability of a system to respond to natural selection
(11-14). This seems
counterintuitive. After all, robustness
is marked by a lack of change so it would seem to work against a system’s
ability to adapt to new conditions and, indeed, it sometimes does (14). However, a biological system that is
relatively insensitive to changes in protein structure, enzyme function,
metabolic flux, developmental pathways, etc., can potentially accumulate a vast
store of hidden variation. As this
variation builds up, some combination of traits may prove more adaptive in the
existing environment or may allow the exploration of new niches. Evolvability and robustness, then, are
closely related phenomena.
Robustness of cultural systems has received very little
attention. However, there are reasons to
believe analogous processes may be at work.
Fischer, for instance, follows four waves of English immigration to the
United States, each from different regions of England, and shows not only that
the distinct folkways of these immigrants survived the Atlantic crossing, they
spread out from their initial settlements and persist into modern times,
accounting for regional differences in such diverse cultural traits as cooking
habits, architectural practices, attitudes towards democracy, egalitarianism
and much more (15). In a similar vein,
Nisbett and Cohen argue that regional patterns of violence committed by white
males in the United States are the result of persistent differences in
conceptions of honor. Southerners are
raised in a “culture of honor” that expects men to respond to personal insults
swiftly and, if necessary, violently.
These practices were adaptive within the context of the Celtic herding
cultures that settled the south since mobile wealth in the form of cattle is
relatively easy to steal and must be actively defended. However, these practices have persisted long
after most people have given up herding as a way of life (16). Finally, Putnam follows the progress of
regional governments in Italy from their establishment in the 1970s. Almost without exception, regional
governments in northern Italy function better than those in the south by any
number of objective standards. This
holds true despite the fact that all regional governments began at the same
time, with nearly identical constitutions and with similar funding. Putnam attributes these different outcomes to
differences in the way that social capital is activated in these regions,
patterns of behavior that can be traced back 500 years or more (17).
Clearly, the historical trajectory of a society is critical
to its development and evolution. North
refers to this as path dependence and he argues that failure to take it into
account can render any attempt at institutional change futile (18). All too often social reformers expect that
changing formal rules is sufficient to bring about change. They frequently fail to realize the power of
informal rules, social norms and historical patterns to resist such
attempts. Even if they do appreciate
these recalcitrant forces, there is, as yet, no comprehensive theory that
accounts for cultural robustness in a way that can help manage it. However, if the same general processes that
lead to robustness in biological adaptive systems have counterparts in cultural
systems then there is cause to hope that cultural robustness, properly understood
and managed, might lead to greater cultural evolvability.
To date, so little work has been done in this area that it
will likely be many more years before any attempt can be made to develop a
comprehensive theory of cultural robustness.
My work includes three ongoing projects that represent first steps that
will hopefully pave the way toward a more unified theory. The first project, “The Role of Religion in
Managing the Commons,” looks at institutional practices that can be regarded as
cultural adaptations that function to allow groups to sustainably manage their
resources. If perturbation of these
practices leads to poorer outcomes, then that suggests a role for natural
selection in maintaining adaptive social practices. The second project, “Exploring the Semantic
Space of Ritual,” looks at how frequency of repetition affects transmission of
cultural practices. This represents a
first step toward understanding if cultural systems have evolved to be robust to
errors in transmission in ways analogous to the mechanisms employed by
biological systems to minimize the effects of errors in DNA replication,
transcription and translation. The third
project, “Tight and Loose Congregations:
Why They Are Different and Why they Coexist,” explores how groups manage
individual autonomy and group conformity.
Note that all three projects involve detailed examinations of the
proximate mechanisms that enable groups to function as cooperative units
adapted to specific environments. This
level of description is needed to understand how robust elements of a system
interfere with evolvability in some cases but enable evolvability in others.
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