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Since Bentley and Shennan’s work demonstrating that random copying processes generate power-law frequency spectra, a significant thread in cultural transmission research has focused on the shape of frequency distributions. In my previous post, I cited Mesoudi and Lycett’s (2009) paper in passing, and in this post I want to highlight an issue that constitutes an important open problem in transmission modeling.
Mesoudi and Lycett note (p. 42) in passing that “perhaps some mix of conformity, anti-conformity, and innovation combine to produce aggregate, population-level data that are indistinguishable from random copying.” The authors go on to note that this claim has not been tested explicitly, and I believe as of this writing (Dec 2010), that this still constitutes an open issue.
I’ve been re-reading a lot of the cultural transmission literature lately, in preparation for a writing project, and anthropologists (including archaeologists) working on CT tend to discuss unbiased transmission (or random copying, to use Bentley’s term) and drift as if they referred to the same thing.
They don’t.
For example, in their superb article “Random copying, frequency-dependent copying and culture change,” Alex Mesoudi and Stephen Lycett say: ”In recent years, several studies have … proposed that the frequency distributions of various cultural traits … can be explained using a simple model of random copying, the cultural analogue of genetic drift.” (p. 41-42, references omitted for clarity, italics in original). I use Mesoudi and Lycett’s quote because it is particularly clear in drawing this parallel, but one can find similar statements throughout many other works on cultural transmission, particularly since Bentley’s work on power-law frequency distributions.
The problem is, “random copying” and “drift” have nothing to do with one another, except possibly the statistical properties of their effects upon a well-mixed population.
