quote:
Zhimbo doesn't have to propose a developmental pathway for anything except an organ of sight, and Joralex seems to find it unfair that the evolution of the entire neural network doesn't have to be explained in detail.
I will agree with NosyNed that it is necessary, in order to adequately explain the evolution of the eye one must show that the "eye" is useful, which means that there must be some reasonable mechanism to allow "sight" to affect the behaviour of the organism.
Zhimbo did this in his first post:
Consider a small, transparent, aquatic, motile organism. A molecule that is in a pathway that affects motility become photosensitive due to a mutation. (Alternatively, it may become sensitive to a photosensitive chemical already present in the cellular environment). Thus, when in light, the motility biochemical pathway changes. In the presence of light, the organism either 1) slows down or 2) speeds up. If the organism photosynthesizes, then option 1 is adaptive, as the organism now tends to stay in light and move out of shadow. Alternatively, if the organism, say, filter feeds but is more visible to predators in light, then option 2 is adaptive. The organism now tends to stay in shadow and move out of light.
A wonderful scenario, in my atheist/humanist/conspiratorial biased opinion. I thought that Joralex merely missed the point and I was going to criticize your post, MrHambre, until I read Joralex's reply a bit more carefully and saw that Joralex dismissed Zhimbo's scenario with:
Consider my POINT 1 and think about the complexity contained therein....I don't disagree at all but you are hand-waving over a huge amount of complexity. The devil is in the details and you're skipping over most of them.
So now I agree with MrHambre. Joralex seems that he/she is going to just dismiss this example with no real argument. The reference to Point 1 seemed to concern a much more complex visual system than Zhimbo was talking about in his initial example - the topic here is supposed to be: "How can a visual system evolve?" Zhimbo needs to come up with a plausible candidate for a first system. The complexity mentioned in "point 1" is not relevant for this example - it may be relevant if the discussion moves to discuss how this initial first system may evolve into the more complex systems, but is not relevant here.
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