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Name: cassy mason
Status: student
Age: 14
Location: N/A
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Date: 2000-2001

Why do snakes not have legs?

Why do you not have wings or a tail? Why do fish not have a beak? Why do chickens not have teeth? If you're interested in questions like this you should read work by Stephen Jay Gould, for instance his book 'Hen's teeth and horse's toes'.

He explains that all vertebrates are 'designed' according to a ground pattern with extensive variation in the details. Snakes developed into a life style in which they didn't need legs, but a very flexible spine. Eventually the legs disappeared, as with the tail of primates.

By the way, my biology tutor who is a famous molecular biologist taught me never to ask 'why' in biological matters. The question imposes there must be an intention, a plan, for something to develop. There may not be such a plan; biology develops into a more or less random directions, and the functionality of each mutation is tested case by case. Look at the present-day sea mammals. They have fins that developed from legs. But going back in the evolution of mammals, their ancestors were fish-like. Would it not have been better if those fishy creatures kept their fins that the seals needed later? This exemplifies that there is no plan in evolutionary biology, just adaptation.

Trudy Wassenaar

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