Evolutionary computation and the Cambrian Explosion

Science news site LiveScience has an interesting article on animals of the Cambrian Explosion. The question they ask is, “Why do these animals look so weird?” Their answer is that the older an organism is, the more changes life on Earth has had to adapt to since the organism appeared. This is accurate as far as it goes, but it doesn’t address the underlying structure of the evolutionary process, and why they look that way in the first place.

Let’s see if this approach will work

Evolutionary computation is a broad field dedicated to applying concepts gleaned from Darwinian evolutionary theory to the development of useful computer programs. The main processes are Recombination and Mutation, to generate diversity, and Selection (AKA survival of the fittest), to maintain evolutionary pressure. You mix and match some diverse population, sort them by fitness, and kill off the least fit, rinse the blood off and repeat. Since this all happens inside a computer, it is not nearly as red in tooth and claw as real nature is.

But in order for all this to work, you need to start with a diverse population. How do you do that? Well, the standard computational approach is to generate a population at random, without any thought to how well or poorly any individual may do. Most, probably all, of that first generation are seriously unfit for the task you have set them. That’s OK. The selection process will give you the best of a bad lot, and recombination/mutation/selection can take it from there. But that first generation is going to look seriously weird.

Jump back half a billion years or so, to the pre-Cambrianites, and you find a bunch of single-celled bacteria, with here and there a soft-bodied multicellular confederacy. There were many, probably thousands, of different species, all of which look pretty much the same in the fossil record but which were actually quite different, with different tools available for experimentation. And then something changed.

Two somethings, to be simplistic about it. First, the climate warmed, due to geological changes. Second, one species of bacteria, cyanobacteria, stumbled on how to use light and carbon dioxide to provide themselves with food, releasing oxygen as a waste product. On the one hand, oxygen was toxic to a whole range of organisms, but on the other hand, it was an amazing power source, if you could harness it. Selection pressure just got intense.

That selection pressure, combined with a wide range of new ecological niches made it possible for life to start a whole new era of evolutionary development. And what life started with was a large, diverse, one might even say weird population, ready to line up for fitness testing.

So the answer to the LiveScience question isn’t just the long time between us and the Cambrian, it also has to do with the diverse, let’s try anything approach that life takes at the beginning of a new era.

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