From: utzoo!decvax!decwrl!sun!megatest!fortune!hpda!hplabs!hao!menlo70!sytek!zehntel!tektronix!ucbcad!ucbvax:G:alpines
Newsgroups: net.jokes
Title: Toilets and Wheeled Elephants
Article-I.D.: populi.553
Posted: Tue Apr 19 00:58:18 1983
Received: Fri Apr 29 11:03:06 1983


On the way home tonight, as I was getting on the bus, a man
was getting off with a toilet, muttering that he had to carry
it around so that he could [pardon me] shit . . . .

And further, this week's Nature which I opened when I got
home contained a fascinating article, excerpted rather for
my own humorous aims below, on the News and Views',
 Page 572-573, by Jared Diamond, Professor of Physiology,
 University of California Medical School, Los Angeles.]Most inventions that have proved useful in human vehicular
transport were anticipated by nature. . . . Why did evolution
not anticipate the most important element of human transport,
the wheel?  Why do rats not roll on wheels but run on feet,
and why are there no propeller-driven fish?  The answer to this
seemingly frivolous question is more complicated than one might
at first think.Almost all our land vehicles are wheeled, and many of our sea
and air vehicles are driven by propellers.  These and other
rotating systems have two key virtues for transport: they subsitute
rolling resistance for sliding resistance and their kinetic energy is
constant rather than fluctuating.  The table illustrates these virtues
by comparing energetic costs of transport for vehicles living and
non-living.  The most efficient known vehicle is a human on a bicycle,
requiring only one-fifth of the energy of the same human walking.
[The table includes other interesting facts:  the cockroach expends 65
calories per gram per kilometre to walk, the rabbit 4.5, a Sikorsky
3.5, a Cadillac 0.8, a human walking 0.75, a human in a wheelchair
0.57, a salmon 0.4 and a human on a bicycle 0.15.] . . .The table suggests that animals would have been better off if they
had evolved the wheel.  Conventional wisdom answers that this was
impossible, because blood vessels and nerves cannot pass through a
rotating joint to supply nutrients and commands to a living wheel. . . .Reflection suggests, however, that problems of nutrient supply . . .
cannot be the sole reason for their non-existence.  Countless animals
bear other non-metabolizing external structures without blood and nerve
supplies, such as claws, hair, scales . . . .  Why have animals not
evolved non-vascularized wheels and propellers as well? . . . For the
purposes of further discussion, let us evaluate a hypothetical rat with
retractable roller-skates on its paws, abbreviated RRR.A recent paper . . . approaches the problem . . . by examining why
animals should not, rather than could not, evolve wheels.  For land
transport [there are] . . . three severe limitations on the wheel's
utility, arising from a terrain's compliance, vertical irregularity and
horizontal irregularity. . . . considerations of terrain compliance select against
roller-skated elephants and favour evolution of wide-rimmed large
diameter wheels for roller-skated rats on soft terrain. . . .The second limitation . . . for wheeled vehicles on land stems from
veertical obstacles. . . . This consideration dooms wheeled ants in
most habitats and frustrates human cyclists and wheelchair-users at
curbs.The third limitation to wheeled vehicles on land comes from obstacles
in the horizontal plane. . . . one can see intuitively that RRRs would
have their roller skates retracted most of the time in most vegetated
habitats. . . .The three limitations on wheel utility for terrestrial animals do not
apply in the sea.  Why, then, are there no propeller-driven fish or
birds? . . . [The] efficiencies for converting input power to thrust
are only about 60 per cent for ship propellers, up to 90 per cent for
typical airplane propellers and 88 per cent for the ingenious propeller
of the Gossamer Condor.  However, an oscillating flexible foil,
analogous to a fish's tail and possibly to a bird's wing, can reach
efficiencies of 96-98 per cent.  Large fish actually achieve these
values.  Thus, the puzzle is not why fish failed to evolve propellers,
but why engineers failed to evolve oscillating flexible foils. . . .In short, animals . . . lack the wheel, not because they could not
evolve or invent it, but because they are better off without it.''

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Seriously, though, it's quite fascinating.  I suggest you obtain
a copy of the entire article and read it.