Anyone else who is reminded of the Mulefa from the book The Amber Spyglass (3rd in the series His Dark Materials by Philip Pullman)? Especially with regard to Cecil’s ultimate reason for not evolving wheels: “no interstates”. In the Mulefa’s world, there are just such interstates, created from lava by volcanic activity.
OK, the Mulefa didn’t exactly evolve their own wheels, using large, round tree seeds instead. But it’s a symbiotic relationship, and the Mulefa’s anatomy has adapted to the “wheels”, so that’s close enough for me.
Quite an ingenious idea by Pullman. It’s a great book series anyway.
The reason no animal has evolved wheels is no animal tissue can deal with continuous revolving. It must stay connected to the body with nerves and blood vessels which have no way of coping with revolving motion other than twisting and they can only take a very limited amount of that. Ponder on it.
Actually, the matter is more complicated than you would think, as developed in previous threads. However, the Search feature here seems still to be hors de combat.
Well, not exactly a wheel, but at least some form of axle has evolved – the bacterial flagellum. Slap something round on it instead of a whip, and you’d have a wheel, essentially.
Which, as I now see, was mentioned in the original article. :rolleyes:
Three cheers for redundancy!
Yay for redundancy!
Yay for redundancy!
Yay for redundancy!
Either Omni or Discover had a great article The Rat With Retractable Rollerskates. It dealt with the objection that nerves and veins would get tangled by postulating wheels of horn. The conclusion of the article was that there were not enough environments suited to wheels, thus no advantage to having them.
I’d have to go with “What’s the great advantage in having wheels”? Most of the reasons they’re useful for us can’t be applied simply to nature: e.g. It’s hard to engineer a machine that balances on legs – but in nature balancing on legs happened long after the limb design and brains with complex control mechanisms had been established, so that cost is pretty much irrelevant.
Perhaps limbs are just the way things panned out here on Earth. So, on another world, perhaps early life might evolve a wheel-like flagellum and subsequently complex multicellular life might evolve with many variations on the wheel design, instead of many variations of the limb design.
Simplicity of wheel is misleading. Effective wheeled movement requires actually a lot of quite complex mechanisms.
The wheel itself - need to be round enough, durable and with good traction. And you need at least three of them.
Axle/bearing - probably hardest part to evolve. Impossible to be made without some kind of tissue discontinuity [solutions: wheels are dead tissue (but can’t regrow if damaged); chassis is dead tissue (and wheels itself are alive, a’la rolling coral colony); wheels and chassis are alive, but separate (although symbiotic) organisms.
Power - you need to make them roll. There is not much ways to make it effective. Maybe some kind of pusher parapodia. Or, in case of living wheels, contractions of muscles making them to change their shape in a kind of rotating wave.
Brakes - you don’t want to uncontrollably roll down any slightest slope. Might be alternate function of power mechanism.
Steering - either by differentiation between left side/right side wheels (hard to do with separate living wheels) or changing wheel direction (hard to do with dead tissue chassis).
Also ecosystem - you need mostly flat terrain without any kind of ridges. Dry riverbed is end of road for wheeled animals, but only minor obstacle for legged ones.
You need to evolve all of the above at the same time, all while outcompeting legged animals. Impossible? Probably no. But certainly very, very, very improbable.
Actually, this is not necessarily true. But the Search feature is still broken, so I can’t find the thread where this was discussed in full a year or two back.
