Zoological artist

Evolution never happened by taking one adult form and coaxing it into the shape of another. Remember that every adult grows as an embryo. The mutations selected would have worked in the developing embryo by changing the rate of growth of parts of the body relative to other parts. In Chapter 7 we interpreted the evolution of the human skull as a series of changes in the rates of growth of some parts relative to other parts, controlled by genes in the developing embryo. We should expect, therefore, that if we draw a human skull on a sheet of 'mathematical rubber', it should be possible to distort the rubber in some mathematically tidy way and achieve an approximate likeness to the skull of a close cousin, such as a chimpanzee, or - perhaps with a bigger distortion - a more distant cousin such as a baboon. And this is just what D'Arcy Thompson showed. Note, once again, that it was an arbitrary decision to draw the human skull first, and then transform it into the chimpanzee and the baboon. He could equally well have drawn, say, the chimpanzee first and then worked out the necessary distortions to make the human and the baboon. Or, more interestingly for a book on evolution, which his was not, he might have drawn, say, an Australopithecus skull first on the undistorted rubber, and worked out how to transform it to make a modern human skull. This would surely have worked just as well as the pictures above, and it would have been evolutionarily meaningful in a more direct way.

G cry an Pnralomi*
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D'Arcy Thompson's crab 'transformations'

D'Arcy Thompson's crab 'transformations'

human ihmm panzer baboon

human ihmm panzer baboon

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