I’ve just begun reading your latest book, The Straight Dope Tells All. On page two, while ruminating on the subject of “questions…that give you pause,” you write, “The other day someone writes in and says, ‘If making a robot limb is so hard but other types of machines are easy, how come no animal species has ever evolved wheels?’ Had to think about that for a while.” You then go on to answer a completely unrelated question. Could I trouble you to answer the question you were asked?
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For starters let’s concede the original writer’s premise. Robot limbs that faithfully duplicate animal motion are a design nightmare. Coordinating multiple limbs, maintaining balance–if you think that’s easy, try it after you’ve had a few brewskis. Remember the walking war machines in the Star Wars movies? One reason they were so striking was that they had no real-world counterpart. We use wheels for our vehicles because rolling is so simple. Why doesn’t nature?
You might say: Because it’s impossible. How would such a wheel evolve? Many intermediate steps would be required, but until the proto-wheel became functional (semi-techie talk coming up here), it would be useless baggage offering no selective advantage.
Don’t be so sure. A flesh-and-blood wheel might use the umbilical hookup found on some merry-go-rounds. Tape one end of a piece of ribbon to a tabletop and the other to the bottom of a compact disc. Turn the CD over so that the ribbon drapes over the side. Now move the CD so that it “orbits” the ribbon clockwise, at the same time rotating the disc clockwise, two rotations per orbit. (Not the easiest thing to explain without diagrams, but think of it as an IQ test.) The wheel turns, but the ribbon doesn’t twist. Would it be easy for a living wheel to evolve something along these lines? Maybe not, but who’s to say it’s impossible? (Thanks to Usenet denizen “softsofa” for reminding me of the preceding demonstration.)
