Speech: Richard Dawkins explains the adaptive valley

I want to spread the ideas of others, but I don’t want to plagiarize them. So, for the next few weeks, I will run a series called “Speech Highlights” wherein I’ll link to some fascinating speeches and discuss them.

First up: Biologist Richard Dawkins demonstrates the evolution of the eye:

  • The eye is often said to be an example of irreducible complexity. Richard Dawkins explains that this claim is bogus. Living things display complexity that is surprisingly reducible.
  • You start with a simple sheet if light-sensitive cells. You then develop a shallow cup that, by casting a shadow, indicates light direction. The cup then progressively expands to cast more precise shadows which the organism can use to accurately predict light direction. Animals with eyes of this type exist.
  • That form of eye that Dawkins first described is less than optimal, however. The lens is superior.
  • Dawkins then explains the adaptive valley, which he calls “mountain probable”. I have written about the adaptive valley, starting here.
  • If lens eyes are superior, why do some animals have non-lens eyes? Why didn’t they evolve the lens? It is because those animals got stuck on a peak on mountain probable. They kept moving upwards, and out of bad luck, ended up with an inferior adaption.
  • I like this video because it illuminates the connection between the adaptive valley and accused “irreducible complexity”. A trait can be both possible to gradually evolve and also hard/impossible to gradually improve. That is to say, if your starting point is a peak, than another peak looks irreducibly complex.
  • Dawkins then explains the evolution of the eye lens, to show that it too is not irreducibly complex.
  • A computer model has simulated the evolution of the eye. Even erring on being slow, the models showed that the eye can evolve surprisingly quickly. The model was I presume a genetic algorithm. If you know how genetic algorithms work, you might like my post on AI.
  • Eyes are so easy to evolve that amazingly varied forms of them are present on different species.

This is a short speech/demonstration to start off. Check this website for increasingly in-depth speeches.

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