Wednesday, 31 August 2011

Tim Tyler: Memetics features directed mutations


Hi! I'm Tim Tyler - and this is a video which responds to one of Steven Pinker's criticisms of memetics - the one where he points out that memetics features directed mutations.

In my book on memetics - which is out now - I take a look at some of the critics and criticisms of memetics. Steven Pinker is one of these critics. Pinker expressed a number of objections to memetics in a 2009 Harvard lecture. Here we will look at his claim that memetics features directed mutations. Here's Steven next:

[footage of Steven Pinker saying things including:]

Design without a designer is essential for biological evolution - but it is peverse for cultural evolution: there really is a designer - the human brain - and there's nothing mystical or mysterious about saying that.

OK - thanks very much for that, Steven. It is true that memetics features directed mutations. However, directed mutations are simply not prohibited in evolutionary theory. It is easy to verify this by looking at the definitions of the term "evolution" in the textbooks on the subject. Not a single one of those definitions makes any mention of mutations being "random" or "undirected". They just talk about variation. Non-random sources of variation are absolutely permitted in evolutionary processes - according to standard definitions of the term "evolution" in the textbooks on the subject.

In the organic evolution of genes, mutations are typically perfomed inside cells. They are far from random. The effects of organic mutations are, in fact, biased towards being adaptive, compared to what the effects of random mutations would be. This is true because the cell controls how its error detection and correction machinery is deployed. Consequently, cells have a variety of mechanisms to prevent the most damaging kinds of mutations - namely mutations to expressed genes. Some of these mechanisms have been clearly documented by scientists working in the area so, we know for example that some base pair sequences are more prone to trigger mutations than other ones. The redundancy in the genetic code allows coding genes to systematically avoid being mutated by steering clear of these mutation-prone sequences.

In meme evolution, mutations are typically perfomed inside brains. Consequently, a much wider array of mutations is available, and mutations can be made using the principles of engineering and intelligent design. So, in memetic evolution, there are indeed intelligent designers. That is just fine, and it does not represent some kind of problem.

Just because directed mutations exist, that does not mean that natural selection is no longer important - just that it is not the sole star of the show.

For example, the design of a video player may involve intelligent design. However, if you look at the VHS vs Beetamax battle, the outcome of that is the result of a selection process, not the consequence of design. So there is still a substantial role for selection to play in determining the form of the things that we see. That is why you need evoution as a base theory. Changes by intelligent agents are modelled as a type of directed mutation - and evolutionary theory is absolutely OK with mutations being directed - that is not forbidden at all.

Introducing directed mutation does not gut the theory of natural selection of its explanatory power. Nor does it entirely take over the role of explaining the form of things that exist. Directed mutations explain some of the features of the resulting products, and selection explains some of their other features. To explain the observed results you plainly need a theory that models both selective and mutational processes - and evolutionary biology is that theory.

In the case of the VHS vs Beetamax battle, the individuals doing the selecting are intelligent agents - namely consumers - but intelligent agents are intimately involved in organic evolution too. Selection by intelligent agents took place throughout human evolution. Human sexual selection was selection of intelligent agents by other intelligent agents. Any idea that organic evolution is somehow "blind" is just bunk. In organic evolution, mutation may not typically involve very much intelligence, but selection very often does. That does not imply that the selection was done by "deities with foresight" or "cosmic engineers". The selective agents were intelligent humans - and it is perfectly permissible to invoke intelligent agents who influence the evolutionary trajectory because the process of natural selection gave them to us. This argument that allows us to invoke the actions of intelligent agents in organic evolution is exactly the same as the argument that allows allow us to invoke intelligent agents in cultural evolution. The time when we are not allowed to invoke intelligent agents in evolution is before intelligence evolved. However, we have had intelligent agents for millions of years, and they have been influencing the path taken by evolution since they arrived on the scene.

Of course, if you bother to unpack the process going on creating something like a VHS video recorder you will find that the process that created it involved a vast amount of trial-and-error testing:

The companies involved in designing them were the result of trial and error in the marketplace, based on their previous products.

Within the company, there was a selective retention process which was responsible for deciding which engineers were employed by the company in the first place. Another similar process which influenced which of the employees worked on the project.

More trial, error and selective retention was employed by the engineers involved in attempting to find out what works and what doesn't by using testing procedures.

This was then followed by selective rejection of what didn't work and the perpetuation of what did by supervisors and managers.

Also, if you look inside the minds of the human engineers involved, you will find that there's an iterative generate-and-test process going on in there as well. The mind contains a virtual world which allows possiblilites to be tested and rejected rapidly in a virtual environment. The mutations involved at that level are typically generated rapidly - and without very much intelligence - and are then filtered by selective processes.

And at lower levels in the brain, there are still more instances of variation followed by selective retention - in the case of axon tips competing for dendrite attachment points and dendrite bodies dynamically competing with other dendrites from the same neuron for resources.

So, you really have a form of natural selection taking place at each level.

However, that's really more of a topic for another video. Or if you prefer, my Memetics book has a whole chapter about processes of selection in the mind and brain - check it out.


Pinker's entire critique may be found here.

No comments:

Post a Comment