(it’s designed to)
These are some thoughts prompted by the recent article Arrival of the Fittest:
Robustness and flexibility are basic design principles. We design modules so that they are robust against minor damage, bad inputs and changes in other parts of the code. This aids ‘evolvability’ of the whole by untangling the knots so that parts of the design can be worked on independently.
Think of Dawkins’ METHINKSITISLIKEAWEASEL parable. The string of text can evolve because each letter is selected independently. The system is designed to evolve. By contrast, in an undesigned bag of chemicals or genes you would have all kinds of cross interaction which means a change in one chemical could have wide-ranging unpredictable effects. The chemical/genetic cross interactions are like encryption: it scrambles and mixes the information, making it non-robust, and ‘sticky’ – non-evolvable. Evolving an undesigned chaotic system is less like selecting individual letters, but more like selecting for the meaning of an entire encrypted message. That is (obviously) not going to work. Nature tends to scramble its ‘codes’. Designers work hard to unscramble/untangle interactions because that makes it easier to make changes without destroying the progress already made in other parts. Why would evolution act to untangle interactions? It cant, it can only make use of the non-tangledness which leads to robustness if it finds it by chance. Once evolution finds it, and if it can keep it for long enough, there would be an accidental selection effect as it starts to find new directly-selectable solutions faster. I think this must be the idea that the author (Wagner) has in mind.
The problem is that robustness aids progress but is not enough to drive it. The key question that determines whether evolution can lead to progress or not is whether innovations are readily accessible. Robustness helps design, but it is obviously not enough to replace it. However, if it is also true that there is ‘treasure everywhere’ when then of course gradualistic evolution is possible. If there are myriad little machines that just happen to contain increasing numbers of the essential parts of a flagellum, then of course a flagellum couldd eventually result, and this is precisely the kind of scenario that most internet Darwinists imagine.
But is it true? There is no a priori reason to think so, and Lenski, for example, is doing a sterling job of proving to the world that there just isnt ‘treasure everywhere’ to drive evolution. Treasure is rare (or designed).