Monday, 10 February 2014

Nijmegen Lectures - Day 3: The evolution of culture without miracles

Part of the Nijmegen Lectures 2014, given by Professor Russell Gray. See previous post

Bio-cultural analogy

On the third and final day of the Nijmegen Lectures, Russell Gray expanded on the evolution of culture ‘without miracles’. There has been a debate for some time whether cultural evolution can be likened to biological or genetic evolution. Darwin himself had this to say about it:

"The formation of different languages and of distinct species, and the proofs that both have been developed through a gradual process, are curiously parallel." (Darwin, 1871)                                         
 A few of the major arguments against the analogy are:
  • Variation in cultural ideas is not as random (as genetic mutations), but rather intentionally designed
  • Cultural features have low fidelity transmission, including:
    • Information loss
    • Vertical AND horizontal transmission
    • Blending (copying one ancestor, like genes, but also copying many ancestors, unlike genes)
People from a tribe in Northern Thailand (August 2008)

Transmission fidelity

Russell discussed these points briefly in his lecture. He brought forward some ideas from Dan Sperber's 'Explaining Culture' (book) to show that perhaps we should not see cultural variance as being replicated or copied, but rather as interpreted, or reconstructed. When you reconstruct, you can take a lot of variants you come across, and then make your own out of that set (blending) - this suggests a difference from high fidelity copying. Similarly, when we tell stories (a cultural feature), we may not even always tell the same story ourselves. Still, Russell argues, such cultural attractors create discrete units of culture that are stable despite noisy transmission.

One way such units of culture may stabilize could be on the population level: Henrich and Boyd (2002) have argued that accurate replication need not occur at the level of cultural innovations, but rather that conformist bias can stabilize these units at the population level. Prestige bias is another form of such stabilization, whereby the most successful cultural features are blended, resulting in adaptive evolution. In this way transmission fidelity can be very low at the individual level but high at the population level.

Horizontal transmission / hybridization

Another issue is that cultural trees don't just diverge, but syncretize and form anastomoses too (when two branches of a tree come back together again).  In this sense, the tree of culture is a ramification of assimilations and acculturations (Kroeber, 1948). This led Stephen Jay Gould (1987) to oppose the bio-cult evolution analogy; he argued that biological lineages become separate, and don't amalgamate (except through rare hybridization), while cultural evolution has rampant transmission and anastomosis. Russell argued that this judgement was made too fast: while Gould worked on vertebrates, the evolutionary trees of virus are a lot 'messier' and can include horizontal transmission as well (and may be more similar to cultural evolution). 

But most of all we need methods to test these different ideas! We need to develop data and methods to test whether there is cross-lineage transfer, what the fidelity of cultural features is, etc. 

It seems that some cultural aspects show high fidelity transmission - there are certain words in languages in the Pacific that after 446,000 years of cultural evolution are still very similar. That is striking. It may be that some aspects are transmitted with high fidelity (traditional decorations, for example) and others via horizontal transmission (iPods, for example). How can we look at this? Russell suggested that rather than looking at these aspects by means of evolutionary trees or 'waves', perhaps we should use networks (to capture the combination of horizontal and vertical transmission). One way to do this is via NeighbourNet, developed by Bryant and Moulton (2002). 

Network analyses

This method was developed for biological data, to understand bacterial and viral lineage conflicts. It allows one to visualize whether there is strong historical lineage or more conflicting signal. When there is a good match, the data looks tree-like, but when there are conflicting signals, the figure looks more like a network, or a spider web. In this way, hybrid origins of languages can for example also be visualized, which shows up as double lines grouping a language with two sets of languages (parallel lines represent spliuts, and the line length represents the split weight) - see Gray, Greenhill and Bryant (2010). Such a method may prove very useful for the science of cultural evolution, and even the story of Little Red Riding Hood has been analysed with it so far (Tehrani, 2013 - open access article).

So, to round off the final talk of the Nijmegen Lectures, there is some evidence that cultural evolution may be likened to biological evolution - in some case more like the biological evolution of bacterias and viruses. In either case, we need methods to test such ideas directly, and network analyses may be helpful to this regard.

I hope you have enjoyed reading about the Nijmegen Lectures, I certainly enjoyed being there! /V.

P.S. For those readers who have noticed the tags used for this post - what's the difference between 'evolution of culture' and 'cultural evolution'? Merely in terms of blog tags, I am trying to distinguish between discussing (specific) examples of cultural features and their evolution ('evolution of culture') and the discussion of cultural vs biological evolution ('cultural evolution'). Cheers!

Selected references

- Boyd R., Borgerhoff Mulder M., Durham W. H., Richerson P. J. 1997. Are cultural phylogenies possible? In Human by nature, between biology and the social sciences (eds Weingart P., Richerson P. J., Mitchell S. D., Maasen S., editors. ), pp. 355–386, Mahwah, NJ: Lawrence Erlbaum Associates.
- Bryant, D., & Moulton, V. (2002). NeighborNet: An agglomerative method for the construction of planar phylogenetic networks. In Algorithms in Bioinformatics (pp. 375-391). Springer Berlin Heidelberg.
Darwin, C. (1871). The Descent of Man. D. Appleton and Company.
Gray, R.D., Greenhill, S.J., and Bryant, D. (2010). On the shape and fabric of human history. Philosophical Transactions of the Royal Society London, B, 365, 3923-3933.
Henrich, J. & R. Boyd (2002) On Modeling Cognition and Culture: Why replicators are not necessary for cultural evolution. Journal of Cognition and Culture 2(2): 87-112. 
Pagel, M., & Mace, R. (2004). The cultural wealth of nations. Nature, 428(6980), 275-278.
- Sperber, Dan. (1996) Explaining Culture: A Naturalistic Approach. Blackwell Publishers.
Tehrani, J. J. (2013). The Phylogeny of Little Red Riding Hood. PloS One, 8(11), e78871.


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