Thursday, July 30, 2009

177. Music and Cultural Evolution -- Part 4

I deliberately chose the Ik as an example because they represent an extreme case, and the forces driving change are often easier to grasp in their most extreme, and thus most simplified, form. As I wrote in a comment to my previous post,
Of course, the Ik represent an extreme case, and it's not difficult to imagine such a disaster leading to a culture dying out completely. But what if it doesn't die out? What if there are survivors who manage to begin anew at some point, what will they be teaching their children? What aspects of their old culture are likely to survive, what are likely to be lost and what new elements are likely to be introduced?
As far as population genetics is concerned, there is one thing we can say for sure. When a population has been drastically reduced in size, for whatever reason, its genetic diversity will also be drastically reduced, in a type of genetic drift known as a population bottleneck:
Population bottlenecks occur when a population’s size is reduced for at least one generation. Because genetic drift acts more quickly to reduce genetic variation in small populations, undergoing a bottleneck can reduce a population’s genetic variation by a lot, even if the bottleneck doesn’t last for very many generations. . .
Population bottlenecks lead to founder effects:
A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have:
  • reduced genetic variation from the original population.
  • a non-random sample of the genes in the original population
It's not difficult to see how, in a society enduring as much extreme stress as the Ik (and here I am speaking hypothetically regarding the possibility of a parallel situation in the distant past), only a relatively few individuals might manage to survive. As far as the geneticists are concerned, this drastic reduction in size would already, in itself, produce both a population bottleneck and founder effect. But that wouldn't be the end of it, because we are dealing here with a human population, maintaining certain social and cultural traditions that will also, inevitably, be affected. In other words, we can conclude that population bottlenecks will lead to socio-cultural bottlenecks, which will, in turn, produce socio-cultural founder effects.

It's impossible to predict which aspects of the old culture will endure and which will fall by the wayside, as this will depend on the individual characteristics and preference of the survivors. If they are anything like the Ik survivors, however, we can make some predictions with a reasonable degree of confidence. For one thing, if their old, pre-bottleneck culture were as communal as that of most African societies, many if not all these communal values might well be lost. If, like the Pygmies and Bushmen, and so many other hunter-gatherer groups, they were in the habit of sharing all food and other goods equally among themselves, with no thought of repayment, one might expect a very different sort of "economic" code among the bottleneck survivors. If they had been non-violent and cooperative in the past, one might expect that the survivors would not only be more prone to violence and less cooperative, but that they would also place a social value on both violence and self-interest, a value that might well be reflected in a new set of myths, legends and other traditions to be passed on to future generations.

Musically, one could predict the loss of certain elements that might have been a part of the older tradition. Certainly if they had been in the habit of singing in P/B style, or something resembling it, there would be a considerable loss, simply due to the breakdown of communal life. We might well expect far more emphasis on solo singing, with unison being more likely than polyphony in cases where group singing might be revived. As I see it, and I think this hypothesis can be supported from what we already know about the musical "evolution" of many groups, Joseph Jordania's observation regarding polyphonic singing makes a great deal of sense: once the habit of singing spontaneously in harmony (i.e., polyphonically) is lost, it will never be regained -- not at least in the most traditional societies.

One more thing to keep in mind. Regardless of the cause of the initial population bottleneck, once the new set of traditions is established by the surviving founder group, there us good reason to believe that the new traditions will tend to persist unchanged, even after the conditions that led to the bottleneck improve. Seen from this perspective, therefore, it appears as though culture, contrary to the assumptions of functionalism, is not determined so much by the environment as by a very fundamental principle, far too neglected in our time, the sheer inertial force of tradition. This is of course a hypothesis, not a rule, as there is still much to be learned about cultural evolution. It is, however, a testable hypothesis -- in the testing of which the musical evidence is now playing a crucial role.

5 comments:

Maju said...

I have to correct you in one thing: population bottlenecks do not lead to founder effects, they are similar in their effects. You could even say that a founder effect is a special kind of bottleneck, one in which the cause is not catastrophic (typical bottleneck) but migrational.

There could be a third bottleneck-like effect that is just caused by low population densities: fixation because of extreme drift. Drift can easily neutral or quasi-neutral genes to vanish and drift can be very intense in small hunter-gatherer populations.

In all cases diversity is lost. The causes and the sociological impact of the process would be very different though.

In relation with this, one can think of cultural founder effects (example: the flautist of the village is the one to emigrate, not the drummer: the new culture will be more prone to use flutes than drums probably) and cultural drift: among the array of individual decissions on the cultural background (which story to emphasize, which music to favor), some may have more impact in the long term for not reason at all - the pattern is not predictable but chaotic.

The same that is extremely difficult to discern the causes of the different bottleneck-like effects in genetics, I can imagine it should be difficult to discern them in the socio-cultural tapestry, right?

DocG said...

I think the problem is that the terminology is itself confusing and somewhat contradictory, Maju. But you do have a point. I think the essential difference is that a bottleneck can be understood as an event that occurred to one particular group (or lineage) which suffered some sort of disaster and then recovered, with a much smaller population than before. However, there are cases where there was no disaster, but a new population was founded due to a rift of some sort, where a small group or family breaks off from the others and founds a new lineage based on a greatly reduced gene pool. I think there is some confusion in the literature as to whether or not this second situation should be referred to as a "bottleneck" as well. I tend to refer to both as bottleneck situations, because both involve the same sort of reductions in population and genetic/cultural diversity. And I see no way of distinguishing between the two when examining the genetic or cultural evidence -- but perhaps I'm missing something.

It seems clear to me that both situations lead to founder effects, so I'm not sure why you want to reserve this term only for the second possibility.

In any case, this is merely a terminological difference, I would think, so maybe we can just agree to disagree on the terminology?

"In relation with this, one can think of cultural founder effects (example: the flautist of the village is the one to emigrate, not the drummer: the new culture will be more prone to use flutes than drums probably)"

Yes, exactly, this is an excellent point. However, I see no way that such an event would not produce a genetic "bottleneck" (or if you prefer "founder effect") as well as a cultural one. From a pop. gen. viewpoint, such a migration would produce a founder effect that ought to be traceable thousands of years later in the genetic profile of the flute player's descendants. And from a comp. mus. viewpoint, the same event should be traceable thousands of years later in the musical profile of his (or her) descendants.

And I would agree that the processes that lead to both pop. bottlenecks and founder effects, both genetic and cultural, are unpredictable. We certainly have no way of knowing why the flute player decided to gather his family and leave, in order to found a new lineage somewhere else. However, there are cases where we might be able to meaningfully speculate on the possible causes of a major disaster that could have led to bottlenecks and/or founder effects.

Maju said...

I was basically disputing the "bottleneck leads to founder effect" idea that is confusing (and surely confused) in itself. Otherwise no big deal.

It seems clear to me that both situations lead to founder effects, so I'm not sure why you want to reserve this term only for the second possibility

It's, I guess a technicality: while you could argue that a founder effect is special type of bottleneck (the population loses diversity in any case, even if the cause is not a massive disaster) or you could argue maybe that a catastrophic bottleneck is special case of founder effect, saying that one thing leads to the other in a causality chain really beats me and makes my eyes bulge out.

...so maybe we can just agree to disagree on the terminology?

Guess so.

Yes, exactly, this is an excellent point. However, I see no way that such an event would not produce a genetic "bottleneck" (or if you prefer "founder effect") as well as a cultural one.

Indeed. You are right in this. What I mean is that, the same you may have a hard time differentiating the causes of bottleneck-like situations in genetics, you should have the same difficulties in pinpointing the causes of cultural bottlenecks. I can imagine, for example, that the same that "random" drift can cause a de-facto genetic bottleneck (fixation), specially when population levels are very low, that same drift could cause de-facto cultural bottlenecks. Same for founder effects (migrations).

I can only imagine that is the main objection you'll get from other anthropologists that may be sceptical or critical of your research.

Guess that you adopt two positions in this aspect:

1. Assume it is not easily discernible and just talk of genetic and cultural bottlenecks (in the wide sense), without digging too much in their possible triggering events
2. Try to discern the different situations with some kind of method (no idea which)

Probably I'd adopt the first position, at least in general, as it's the cautionary approach. Though if I think I can identify the causes of some of these processes, I'd also mention it, but making it clear that it is largely speculative and not the essence of the research

Maju said...

Erratum:

Guess that you adopt two positions in this aspect:

should read

Guess that you can adopt...

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