richard_dawkins_-_the_god_delusion

130 1 II H t. O 1) 1) !• 1 U S 1O N
credited (if credited is the word) with moving creationism into a
new area of biology: biochemistry and cell biology, which he saw as
perhaps a happier hunting ground for gaps than eyes or wings. His
best approach to a good example (still a bad one) was the bacterial
flagellar motor.
The flagellar motor of bacteria is a prodigy of nature. It drives
the only known example, outside human technology, of a freely
rotating axle. Wheels for big animals would, I suspect, be genuine
examples of irreducible complexity, and this is probably why they
don't exist. How would the nerves and blood vessels get across the
bearing?* The flagellum is a thread-like propeller, with which
the bacterium burrows its way through the water. I say 'burrows'
rather than 'swims' because, on the bacterial scale of existence, a
liquid such as water would not feel as a liquid feels to us. It would
feel more like treacle, or jelly, or even sand, and the bacterium
would seem to burrow or screw its way through the water rather
than swim. Unlike the so-called flagellum of larger organisms like
protozoans, the bacterial flagellum doesn't just wave about like a
whip, or row like an oar. It has a true, freely rotating axle which
turns continuously inside a bearing, driven by a remarkable little
molecular motor. At the molecular level, the motor uses essentially
the same principle as muscle, but in free rotation rather than in
intermittent contraction.! It has been happily described as a tiny
outboard motor (although by engineering standards - and
* There is an example in fiction. The children's writer Philip Pullman, in His Dark
Materials, imagines a species of animals, the 'mulefa', that co-exist with trees that
produce perfectly round seedpods with a hole in the centre. These pods the mulefa
adopt as wheels. The wheels, not being part of the body, have no nerves or blood
vessels to get twisted around the 'axle' (a strong claw of horn or bone). Pullman
perceptively notes an additional point: the system works only because the planet
is paved with natural basalt ribbons, which serve as 'roads'. Wheels are no good
over rough country.
f Fascinatingly, the muscle principle is deployed in yet a third mode in some insects
such as flies, bees and bugs, in which the flight muscle is intrinsically oscillatory,
like a reciprocating engine. Whereas other insects such as locusts send nervous
instructions for each wing stroke (as a bird does), bees send an instruction to
switch on (or switch off) the oscillatory motor. Bacteria have a mechanism which
is neither a simple contractor (like a bird's flight muscle) nor a reciprocator (like a
bee's flight muscle), but a true rotator: in that respect it is like an electric motor or
a Wankel engine.