It has struck me that there are many similarities between the concept of species in evolutionary biology and the concept of cultures in anthropology and sociology, and that evolutionary sociology could benefit from the insights of biology regarding mechanisms of speciation and apply them, not only to understand how cultures form, but to engineer better cultures than existing ones. This has been partially the goal of socio-biology and Dual Ineritance theory (1) but for reasons I speculate on later, neither has looked much at how biological models of speciation can inform sociological models of cultural genesis. Instead the focus has been on other evolutionary mechanisms (but see (2) for a small exception). In this essay I will focus on a sub-topic of speciation, which is reproductive isolation, and try to broadly look at similarities and differences in isolation between species and cultures.
Both species and cultures are ways of grouping individuals who are more similar to each other than to other individuals in other cultures or species. The similarities of the individuals are genetic, phenotypic and behavioral in biology, and behavioral in sociology.
More importantly, cultures and sexually reproducing species are similar in the greater amount of information exchange that happens among them then outside of them. This is known as reproductive isolation in evolutionary biology, because with species the lack of information exchange outside the species (isolation) is extreme (3). The exchange of DNA through sex among individuals in (sexually reporducing) species is analogous to the exchange of ideas and mimicking of behaviors among individuals in cultures. If cultures and sexually reproducing species are similar concepts, one would expect to see reproductive isolation, or its analog in terms of information exchange, not only in species, but in cultures. But there is a lot of variation in how informationally isolated cultures are. There are anabaptist cultures (like the Amish), certain tribes in the Amazon, Basque or Chinese culture many years ago with a lot of isolation, and more cosmopolitan cultures like secular Jewish culture which exchange much information with other cultures. Perhaps the genesis of a culture involves more isolation than its later development, for example Jewish culture started out more isolated as a desert tribe and adapted to less isolation as it was forced to have more interaction with other cultures upon being geographically dispersed from its homeland and dependent on the graces of other cultures. Or else some cultures are more similar to breeds or landraces than species in their ability to exchange information and even hybridize (4). Witness modern american culture, which is a hybrid of european, african, and asian cultures; or catholic culture, which is a hybrid of Pagan and Christian cultures.
The hybridization of cultures to form new (hereditably stable) cultures is an interesting phenomenon, but not one I will focus on here. Historians have already considered this mechanism of cultural genesis (5). Also in this essay I will not pursue issues of taxonomy. I am more interested in what evolutionary sociologists can learn from evolutionary biologists as far as mechanisms of speciation that do not involve hybridization. In that light, reproductive isolation is not only a matter of definition of a species, but of its genesis.
There are 3 detailed mathematical models of speciation in biology, all of which have some empirical support (6,7,8). To understand these theories it is necessary to introduce the concept of adaptive landscapes, which was invented by the evolutionary biologist S. Wright almost 100 years ago.
The adaptive landscape is a function from either gene space, phenotype space, or to make a connection with game theory, hereditable strategy space, to the real numbers, with its value representing fitness, or equivalently rate of growth of populations of individuals (or sometimes populations of groups) (8). If there were only 2 strategies, it would have a nice visual representation as a topographic landscape, with the height representing fitness and movement in the other 2 dimensions representing the proportion of individuals adopting one or both strategies. This concept has been generalized so that the adaptive landscape is dependent not only on the strategy of an individual (or mean strategy of a species), but on the strategies of other individuals within a species and other interacting species in an ecosystem. It is not static but changes with time, as new species come into being, grow and sometimes become extinct, and as resources change (8).
The first model is due to Wright and is very similar to theories of phase transitions in physics. In this theory reproductive isolation of a small group (which is the incipient species) with one or several mutations from a mother species is necessary in order to produce a large enough genetic drift away from the local fitness maximum of the mother species. This genetic drift is akin to brownian motion, or phase-space diffusion in phase transitions (unfortunately, genetic selection is akin to what is known in physics as drift, a source of confusion). It is allows the incipient species to move downhill in the adaptive landscape, against selective forces, through a "mountainpass" (saddle-point), where selection can take over again and lead the incipient species to another maximum where it becomes a bona-fide species. The smallness of the initial group is necessary because the drift is inversely proportional to group size (9). Too big of a group and the mutation leading away from the mother species may be lost. Smallness of the group is no guarantee of fixing the mutation, as drift could just as likely go towards losing the mutation. Similarly, the reproductive isolation from the mother species is helpful (and becomes necessary the bigger the size of the mother species population) because without it the mutation(s) may become lost, swamped (through the mechanisms of genetic drift and gene flow from mother culture) by the non-mutated allele in the mother species. This mechanism is consistent with what is called sympatric speciation.
In the second and third models, the adaptive landscape changes on the same timescale as the genetics (or hereditable strategies) change. In both these theories a form of reproductive isolation is necessary for a new species to arise. In one of these (consistent with sympatric speciation) there is a selection for assortive mating (like wanting to mate with like and avoiding individuals who are very different from oneself) to drive two populations away from a stable fitness minimum towards two distinct fitness maxima, as hybrids would have lower fitness. Assortive mating is a reproductive isolation mechanism, but it assumes that mutations, epigenetic mechanisms or pre-existing variation will find the direction(s) leading to higher fitness. This is not necessarily going to happen if the variation or rate of mutation is too small, because there are so many possible directions to go in strategy space and only one or a few of them lead to higher fitness. It's like finding a needle in a haystack. An effective entropic barrier has to be overcome (10). The faster the mutation rate, or epigenetic change, the faster the entropic barrier can be overcome.
In the third model (consistent with allopatric speciation), the reproductive isolation happens due to a geographic barrier between sufficiently different environments (such as a river, an ocean or a mountain) that allows a divergent evolution that brings the two groups to far enough places in the adaptive landscape, so that they find new maxima in fitness that are still separated even if the geographic barrier is removed, and the adaptive landscape changes (though not to its original form). In this latter model of speciation, the reproductive isolation seems unnecessary and coincidental, but if the two species were somehow able to mix they would have lower fitness than if they stayed separate, because what produces high fitness in one environment is probably not optimal in the other.
A fourth proposed speciation mechanism (really a special case of the other two) called chronospeciation does not require reproductive isolation from an existing species. It involves changes in the adaptive landscape that keep a species at a fitness maximum through time, but the maximum moves far away from the original maximum so that if the current species were able to travel back in time, it would not be able to mate with the original one, being too far genetically (and phenotypically) from it. I don't find this mechanism interesting for practical applications of how to create a new culture in the midst of the old one, though it might be interesting historically. Also, there is not much empirical support for this mechanism. Speciation usually involves a divergence of the new species from another mother species, and a co-existence of the two for a while.
Since we are interested in explaining why some cultures need more or less isolation than others or than species in their formation, we do not need to look at geographic isolation. It is an interesting question why cultures that have been geographically isolated and diverged sufficiently and are brought back together are able to hybridize more than species, but I will not pursue this question here, since I am interested in how the genesis of cultures is possible even without geographical isolation. Therefore, in the following I focus on the first and second model of speciation (without geographical barriers) and try to formulate a hypothesis that allows cultures to form with varying levels of isolation,
If we study the historical record we can see that all of these mechanisms seem to be operating in cultures, but the reproductive isolation is usually not as severe as in species. Why is this so? Two candidate hypotheses can be eliminated quickly as fundamental explanations:
A. If the second model happens, there is less selection for assortive mating in cultures than in species. However, the reproductive units of culture (memes), whether they are considered to be brain patterns, ideas, values, behavioral patterns, or strategies, can change more easily and quickly than DNA. and the difficulty of getting through entropic barriers might be diminished in cultures. Memes may be at one extreme of a continuum starting with genes (hardware), through epigenetic changes (firmware) to ideas (software). So if going through entropic barriers happens faster, there should also be a faster selection for assortive mating. But the reverse is observed.
B. Or else, if the first model is applicable, fitness barriers still exist, but for cultures, the barriers between peaks of the adaptive landscape may be smaller than for species, hence drift is not as important and hence isolation is not as important. Perhaps it is true that fitness barriers are smaller, but why should this be? A more fundamental explanation is needed.
One possibility is that cultures have horizontal (in the same generation) information transmission, as contrasted with sexually reproducing species, which have mostly vertical (from one generation to the next) information transmission, making recruitment from the current population more important. Nevertheless, some bacteria also have horizontal transmission of DNA and short reproductive times, and they still maintain reproductive isolation from other species of bacteria. A tradeoff might exists between recruitment and the energy it takes to invest in the process, especially filtering the right from the wrong allele. This mechanism could be just natural selection, but in the first model this would act to suppress the incipient species/culture and would be counterproductive, as gene flow from mother species/culture plus drift would act just as with vertical transmission. If the scenario of the second model is operative, this mechanism would be equivalent to assortive mating with vertical transmission. Perhaps bacteria have not evolved a good filtering mechanism, and different cultures differ in their isolation by how good a filtering mechanism they have, or other ways of making the tradeoffs involved in keeping out invading strategies. This can be tested empirically from the historical record.
Other tradeoffs may exist in cultures to mitigate the need for complete isolation, such as needing resources from the mother culture. This is an example of a tradeoff of immediate benefit for long term cost (being absorbed by the mother culture).
I propose that the most important feature that differentiates cultures from species is the existence of foresight. If we think of the first model of speciation, in addition to a random walk (genetic drift) in gene (or strategy) space, plus the force of selection (proportional to the gradient of the fitness function (7)), an incipient culture can "see" (through reason and/or inspiration), albeit imperfectly, a portion of the adaptive landscape and keep going in the direction of a mountain pass, against the force of memetic selection away from the current peak. If we think of the second model of speciation, foreseight allows cultures to more quickly find the direction that goes uphill among the millions of other directions. In both these cases, a culture possessing foresight will be able to speciate more quickly than with drift and random mutations alone. Possibilities that lead to worse places could be tried in thought (and more recently computer simulation) and eliminated before trying them "in vivo".
In addition, once a new fitness peak is able to be perceived, the trip through the valley need not be as difficult as without that perception. In other words, the adaptive landscape becomes less steep, which provides a more fundamental explanation than hypothesis B above. Another way to say this is that foresight allows for delayed "gratification" (or more accurately delayed fitness maximization) and the ability to endure reduced fitness and invest in material (hardware) or spiritual (software) infrastructure that would give a selective advantage later on.
The other component that differentiates cultures from species is the ability to learn from the past, or the evolution of memory. Indeed, foresight is dependent on this: memory and foresight work best together. Another way of saying this is that with the evolution of memory and foresight, genesis of cultures has acquired a Lamarckian component, though the Darwinian mechanisms of mutation, selection and drift are still operative and hence some degree of isolation from the mother culture is still important for forming a new culture.
The tradeoff between immediate and delayed fitness optimization, made possible by foresight and memory is akin to other evolutionary tradeoffs, such as between investing in the germline (next generation) and soma (current generation), or group and individual selection mechanisms. It allows for finding a "sweet spot" between the two extremes of no new culture (no isolation and optimizing for current fitness), and a new culture that is too hard to form due to too much hardship/low current fitness (complete isolation and optimizing for only delayed fitness).
A fertile research agenda (and a possibility for "adaptive radiation" of academic niches) in cultural speciation is opened up. Dynamic Game Theoretical and Optimal Control models of foresight and delayed gratification (in addition to the old mechanisms of mutation, selection and drift) could be developed and tested on the historical record and with incipient vs mother cultures such as the ones found in intentional communities. Factor analysis could be performed to rank foresight along with drift and mutation in the formation of new cultures. Conditions such as trust (and the conditions engendering trust, such as Ostrom principles and Greenbeard mechanisms) could be studied for their interactive effects on foresight and delayed gratification.
Practical application include allowing groups who want to form new cultures to deal with the environmental, social and spiritual problems of our time, or groups who want to maintain their old cultures, as much isolation as they need instead of stigmatizing or attacking them, or even forcing them to trade with the global economy. This is an example of generation and conservation of memetic diversity, similar to the efforts of conservation biologists to maintain genetic diversity (though the biologists do not have to fight homogenization or forced gene flow). Another similar application is for intentional communities to intentionally isolate themselves, except for the minimum needed for recruitment and building infrastructure and paying taxes. As I mentioned, thanks to foresight and the need for recruitment, this isolation need not be extreme, and may change in its degree as the community evolves.
Last I would like to speculate on why cultural isolation has not made it into the vocabulary and understanding of how cultures form in the social sciences. Cultural isolation has been proposed by historians in a roundabout way (a new culture arising once the old one is almost dead) (11,12,13), so this is not a new idea, but the evolutionary implications have not been worked out by them, especially in cases where the old culture is still alive. I propose that this blind spot has occurred because:
1. Isolation has gotten stigmatized through cults that use reproductive isolation to attempt new cultures, but often not in the direction of a better (more fit) culture.
2. Isolation has gotten stigmatized through xenophobic tribal behaviors of certain cultures. But isolation does not have to involve xenophobia and the demonizing of the other.
3. A certain breed of Humanist culture (akin to an invasive species) has homogenized many cultures, lately through the carrot of trade, but military sticks have been used as well. One of the mechanisms it uses to maintain itself is stigmatizing isolation.
4. The invasive breed of humanism is popular among economists and politicians and a few influential evolutionary sociologists.
But there are other breeds of Humanist culture that also have the strategy of "live and let live" and appreciate diversity. I hope they prevail.
(5) Carroll Quigley, The Evolution of Civilizations
(8) Evolutionary Game Theory, Natural Selection, and Darwinian Dynamics, Thomas L Vincent and Joel S Brown
(9) Stochastic evolutionary game dynamics, in Reviews of Nonlinear Dynamics and Complexity” Vol. II, Wiley-VCH, 2009, edited by H.-G. Schuster
(10) Van Nimwergen E, Crutchfield J.P, Metastable evolutionary dynamics. Crossing fitness barriers or crossing via neutral paths?Bulletin of mathematical biology 62(6)799-848 (2000)
(11) Giambattista Vico, Scienza Nuova, (1725)
(12) Oswald Spengler, The Decline of the West, (1923)
(13) Arnold J. Toynbee, A Study of History (1934–1961)