Dawkins describes how embryological development is completely local. No master plan: Just many local interactions, each of which is directed by the set of instructions contained therein. Just like a flock of birds flying together so that they look like they are all part of one graceful whole. But they are not: rather, each is following its own set of instructions. True, that set of instructions is the same in kind for each bird. But there is a different instance of these instructions for each bird. Dawkins points out that if you want to simulate the movement of a flock of birds on the 2 dimensional computer screen, you don't write one computer program for the whole: rather, you write one program for one bird, telling it how to adjust to the movements of other birds. Then you clone it for as many birds as there are.
This is an elegant argument against the unity of not just an embryo, but of any organism. Dawkins himself doesn't carry it that far, but there is no reason why one could not suppose that an adult human is nothing more than a set of cells, each of which has its own set of instructions. Cells in different organs or parts of organs may look different from others elsewhere, but that is because they are reading different instructions from the same operations manual, based on differing signals they get from their immediate environment. In such a case, human action is our name for a whole, which, like the flock of birds, seems to more united than it really is. In such a case, there is no such thing as a scientist. What a curious thing it would be if there were science but no scientists! But that would follow. I suppose Dawkins would confidently, and quite eloquently accept this conclusion. But wait--there is no Dr. Dawkins: only his eloquent words, much like the smile of the Cheshire cat.
One can object that this applies embryos but not to adults. But to object thus without explaining why would be to engage in special pleading, the fallacy where one denies that a generally accepted principle applies in all cases except for where one wishes it didn't apply. To avoid this fallacy, one must explain why the line of anlaysis applies in one case and not the other. As soon as I find Dawkins addressing that question, I will post it here.
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