You are near perfect in some ways, ridiculously inefficient in others

Diplodocus carnegieiA few years ago I did some research modelling evolution. A lot of the modelling of evolution is done by physicists not biologists, as we have more of the quantitative modelling and computational skills. One of the things I was looking at was the question of how good evolution is. Basically: Can evolution produce perfection, or because it is blind does it tend to produce highly imperfect bodies?

The answer appears to be that sometimes it produces near perfect solutions, other times the solutions it comes up with are ridiculously inefficient. As part of a final year course, I teach an example where evolution has done an excellent job. This is in the task of detecting light in very low light conditions. In the 1940s Hecht and others showed that in short pulses of light, the human eye could respond to as few as around 5 photons. This is pretty much as good as the laws of physics allow, as I explain every year to our final-year students. It is one of my favourite things to teach. I think the students like learning about how a part of their bodies work.

I was reminded of this by a blog post by a biologist called Wedel. I enjoyed reading it. He studies sauropods. Sauropods were a type of dinosaur; the diplodocus in the image at the top left is a type of sauropod. These had huge long necks. The point that he makes in his fun blog post is that in many animals, including mammals like us and dinosaurs, the nerves that connect our brain to our larynx actually go down from our brain into our chest and back up to our larynx. These are the nerves we use to speak . The post is on a scientific paper, also by Wedel. So the nerves basically go down and back up the necks of both us and sauropods, and in sauropods this can be up to around 28 metres! Given that the larynx is near the brain this is a ridiculously inefficient way of doing things. It is like going from England to France via China.

So, parts of our bodies are near perfection, others are very far from perfection. In the case of the nerve we use to speak the reason for the inefficiency is the way our bodies develop from the fertilised egg that dinosaurs and we start life as. When in the early embryo the nerve starts to develop there a major blood vessels just below what will be our brain, and the nerve runs below these vessels. As the embryo develops these vessels move down into what will be our chest, and the nerve is forced to move down with them. Once it has formed it cannot break and reform.