Saturday, 20 April 2013

Tim Tyler: Boyd & Richerson, Culture and the Evolutionary Process (review)


Hi. I'm Tim Tyler, and this is a review of this book:

Culture and the Evolutionary Process by Robert Boyd and Peter J. Richerson
This book was published in 1985. It is the best book on cultural evolution from the 1980s. It builds on top of earlier work by Cavalli-Sforza and Feldman, who had outlined a similar approach, in less detail in 1981. Boyd and Richerson do a better job than previous authors did of placing their material in its historical context, and offered a better review of other related material.

However, the book has quite a few problems:

It is full of densely-presented mathematical models. I think that these hinder more than they help. Maybe some people will be impressed by them, but I'm not really among them.

The book introduces terminology for cultural evolution. Much of this has not dated well. It uses the term "guided variation" - where, these days, most people would say "directed mutation". The book uses the term "biased transmission", whereas these days we would just say "cultural selection" or just "selection". Hardly anyone uses the term "biased transmission" these days. The book uses the term "cultural parents" and the term "cultural offspring" - but these are not used refer to memes, but rather to their associated hosts. This does not seem like good terminology to me.

The book is almost entirely free of symbiology. This is unfortunate, since any sensible modern theory of cultural evolution must necessarily be heavily based on symbiology. They do mention the concept at one point. They say:

Horizontal transmission is analogous in some ways to the transmission of a pathogen and Cavalli-Sforza and Feldman have used epidemiological models as a starting point for their development of theory. The item of culture being spread horizontally acts like a microbe that reproduces and spreads rapidly because it is "infective" and has a short generation length compared to the biological generation length of the "host". Fads and fashions and technical innovations are familiar examples.

This material is fine - as far as it goes. However three sentences is not really adequate coverage for this concept. You really need to cover cultural parasites, mutualisms, immunity, arms races - and so forth. Many biologists were still getting to grips with the significance of symbiology in the 1980s. However Cloak and Dawkins had previously managed to present a symbiology-aware version of cultural evolution in the 1970s. Boyd and Richerson failed to pick up on this. What do they offer instead? They say:

This does not mean that cultures have mysterious lives of their own that cause them to evolve independently of the individuals of which they are composed. As in the case of genetic evolution, individuals are the primary locus of the evolutionary forces that cause cultural evolution and in modelling cultural evolution we will focus on observable events in the lives of individuals.

This is not a good approach. It is like saying: to study the evolution of smallpox, we should focus on the human victims. The problem with this is that insufficient attention is given to the smallpox virus. You could say that smallpox exhibits horizontal and oblique transmission between its hosts. It exhibits "biased transmission" - due to different levels of resistance from host immune systems. These processes can all be modeled. While this sort of approach would result in some progress, it seems like a fundamentally misguided way of viewing the situation.

Cultural information exists apart from its human hosts. As well as spending some of its time residing in host brains. It exists in libraries, on discs, inside computer memory, in air vibrations and as radio waves. Libraries can burn down, sounds can suffer from interference, and compute memory exhibits senescence. Culture partly evolves outside its primary hosts. The result is a symbiosis between two different kinds of living and evolving systems. If you focus on observable events in the lives of individuals, you are likely to miss all this material.

Though this book presents a closer link between evolutionary processes in the organic and cultural realms than most previous authors managed, Boyd and Richerson don't really take the links far enough.

The main problems seem to be that, at this stage in their thinking, they didn't appreciate symbiology properly, and they didn't understand that evolution happens within minds, during individual learning - as well as between them, during social learning.

The authors have a section at the very start of their book comparing genetic and cultural evolution. They argue that humans get genes from their parents, but their memes come from a range of individuals. However, humans get viral and bacterial genes from a wide range of individuals as well. This is not really a valid difference between genetic and memetic variation. They argue that meme lifespans are different from host lifespans. However, this is true for DNA genes inside parasites too, and isn't a special feature of cultural evolution. They argue that humans get their genes at birth, while they acquire their culture gradually. However, humans acquire DNA genes gradually as well - it is just that these genes are sometimes inside parasites. They argue that cultural transmission occurs after some development has taken place. Yet this too also happens when acquiring parasites. They argue that cultural variation may be affected by life events, and then transmitted to others. Yet again, this happens with parasites. If you consume antibiotics, you may subsequently transmit antibiotic-resistant bacteria that you have acquired during your lifespan to others.

Boyd and Richerson's list of differences between cultural and organic evolution seems almost entirely invalid. This would not matter, except for the fact that much of the project of studying cultural evolution revolves around the issue of what the differences are. Where cultural and organic evolution exhibit the same dynamics, we can mostly use existing models. The rest of the book is largely devoted to mathematical models of the differences they identified.

While it would be interesting if researchers needed a broad array of new mathematics to model cultural evolution, for the most part, the dynamics of cultural evolution are largely shared with epidemiology and symbiology - and models from these fields can be adjusted to deal with culture with relatively minor tweaks - to cover phenomena such as conformist transmission which have few parallels in the organic realm. What needed doing in the 1980s was strengthening and expanding the models of epidemiology and symbiology to cover culture. Instead what we got was an attempt to drive a mathematical wedge between our models of cultural and organic evolution.

In the book, Boyd and Richerson put in a plea for simple mathematical models. Can their approach be excused on the grounds that they are simplifying? Not really. It isn't "simpler" to develop many unnecessary mathematical models based on illusory differences. Rather it results in increased complication through the proliferation of models. Nor is it simpler to only focus on one symbiont in a symbiotic relationship. The result is a byzantine maze of horizontal and oblique transmission vectors. Best to recognise both partners in the relationship and stick to two types of lineage with pure-vertical transmission within each of them. This is what is done with parasites and symbionts in the organic realm. The cultural realm is no different in this respect.

Overall, this was an important book. It probably wasn't as influential it could have been - since its mathematical models and technical style probably presented a barrier for many readers. Still, most modern workers in the field do cite it, recognising its pioneering role. Since its publication, Boyd and Richerson have continued plugging away at the topic. They have produced a steady stream of papers on the subject - including many valuable ones - along with a few more muddled ones. Despite its virtues, this book's problems - or perhaps the perspective of its authors - seems to have resulted in a bit of a hangover for cultural evolution within academia. Dawkins had clearly presented a framework which was more correct in a number of respects many years before. However, over time, these two camp's relationship increasingly turned into a rivalry. Instead of a synthesis, the result seemed to be tribalism and conflict.

The book was probably the first detailed treatment in academia of maladaptive forms of culture - the insight that cloak and Dawkins originally presented. It pointed out that kin selection apples to memes. It applied runaway selection processes to memes. It modeled memetic conformity. It discussed the possibility of memes sterilizing their hosts and diverting their reproductive resources away from gene propagation and into meme propagation. Overall, there is much of interest in it.


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