Mmmmm. Doughnuts.

Nearly finished the Dawkins and he has saved the best until the end. The chapter on the fact that evolution is a terrible designer is very convincing. It goes into how part of the vagus nerve (a nerve that exits the brain directly rather than being a spur on the spinal cord) descends into the chest, loops under various arteries and veins and returns to the Larynx, an unnecessary detour that in Giraffes becomes a screaming extreme, looping all the way from the brain, down into the chest and back up to the throat. The reason for this is that evolution does not design from scratch, it makes heuristic adjustments with the raw material it starts with. Our descent is from fish where the body plan is quite neatly laid out with the various nerves serving the parts of the body closest to them. Mammals have evolved in a way that tinkers with this standard plan and moves the segments about to best fit what the pressure of natural selection forces on it. However, there is no pressure to tidy up the mess that results from the various cablings being stretched to link various body parts which have moved further apart. Internally the whole mammalian body plan has become a tangled mess only topologically related to the simple plan of earlier organisms. The mammal has almost literally tied its internal connection up in knots.

I am surprised that Dawkins didn't actually mention topology. The sudden looping of a nerve over instead of under a particular structure is a busting of topology, like suddenly having a hole through a sphere busts its topology and it becomes a doughnut.

The other wonderful example of how evolution takes the easy rather than the best course is the fact that the nerves exiting from the sensory cells in the retina do so on the side facing into the eyeball and hence towards the source of light, therefore blocking a portion of it and requiring that the nerves find somewhere to exit the eye. This means that the sensitivity of the retina is reduced because of the wires all over the place and there is a blind spot where all those wires are bundled up and fed through a hole where they form the optic nerve. We only see as well as we do because the software of the brain is able to carry our super-fast and super-accurate clean-up operations (Dawkins I think calls this a real-time version of photoshop). There is evolutionary pressure to right the initial mistake of routing the wires on the wrong side because it works and the fact that humans try to make high-quality optics to match that of the eye shows that our eyes are indeed better at seeing than artificial technology designed to do the same.

RD mentions quite a bit about why these mistakes have never been rectified but I like to think that, sometime, a human will be born with a mutation which makes the nerve ending come out of the back of the retina and gives then a level of sight suddenly many times better. The question then is will the brain be able to keep up? We only have clear and accurate vision in a small patch of the retina I think because the brain could not actually process sharp information from all the retina. What we lose in definition around the periphery of the field of view, we make up for with a sensitivity to movement which allows us to direct the centre of vision to that movement. Would a human with the mutation above be mentally capable of processing the higher definition information?

On a similar note, and I may have mentioned this before, I often wonder if a portion of human mental illness is caused by the fact that our brains have to process many more detailed images that all those years ago on the plains. I feel we have to process out much more irrelevance now with the result that brain capacity we used to use for thinking and contemplating is now taken over having to make decisions about what is important.

I did start thinking that quite a lot of software ends up like this. I can see almost a direct analogy between the routing of the vagus nerve and the flow of control through some programs. Whatever we like to think about the efficiency of our code, a lot of it does evolve from previous versions and as such sometimes uses routes which should really be removed. However as we are now looking at programming using a form of natural selection, should we be wary that such programming will produce valid, accurate, working code, code which does the job but is inefficient in the extreme because the equivalent of its vagus nerve gets routed in and out of unnecessary portions of the application?

Anyway, a very convincing chapter. Hopefully I will have finished by tomorrow so I will mention the next book which is a recommendation from Ed and is The Eyre Affair by Jasper FForde and comes physically courtesy of Sefton Library Services so sorry Jasper - it's just the Public Lending Right rather than a royalty.