Does our analysis suggest cultural evolution represents an autonomous system? In other words, once cultural transmission is in place, does cultural evolution generally operate in an ancillary role, handmaiden of genetic adaptation, or does it break free of the influence of genetic evolution completely?
Their answer is:
although cultural fitness is a distinct quantity, if it is not aligned with genetic fitness, then there is genetic selection to change the learning rules that underpin cultural transmission, making minds more discriminating. For these reasons, cultural evolution cannot become completely autonomous. In this, we echo Lumsden & Wilson’s (1981) famous conclusion that ‘genetic natural selection operates in such a way as to keep culture on a leash’ (p. 13)
I'm sorry - but this argument is a joke. It is not logically coherent. A. G. Cairns-Smith pointed out long ago that genetic takeovers were possible - describing the mechanism by which they could happen. The following diagram illustrates the process.
Just because there's selection acting on DNA that acts against it being phased out, that doesn't mean that we are stuck with DNA forever. I'm sure that there was selection on Dodos being phased out - but nonetheless, we don't have any Dodos any more. Just because selection at one level favours some outcome, it doesn't follow that that outcome will happen.
Broadly the same argument that these authors give about cultural symbionts "proves" that parasites will never wipe out their host species. However there are known cases of parasites driving their hosts to extinction. For example, according to a reference given at the end of this article, there is very good evidence that avian malaria and birdpox were responsible for the extinction of a substantial proportion of the Hawaiian avifauna in the late nineteenth century. Parasites can cause population instability that leads to increased risk of stochastic extinction. Or they can just decimate their host populations through gradual attenuation. Extinction of host populations becomes more likely when the parasites have multiple host species - and are not dependent on any one of them. So, when memes are no longer completely dependent on humans for their reproduction - and are capable of reproducing independently via networked machines, that's when the humans should start to watch out.
You can't plan to avoid particular outcomes if you have a theoretical precommitment to the idea that those outcomes are impossible. The idea that Wilson's leash is necessarily a permanent restraint is not just a silly mistake, it is a dangerous delusion - which it is important that not too many people buy into.
The analysis by these authors is so bad, its embarrassing. Cultural evolution really can help us to understand and navigate the future evolution of the human species. Just because some people have managed to mis-apply the theory and come to silly conclusions, that should not be taken as a reflection on the whole theory.
- McCallum, Hamish (2012) Disease and the dynamics of extinction Phil. Trans. R. Soc. B 19 October 2012 vol. 367 no. 1604 2828-2839.