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Matthew asked:

The evolution thing

Well, I don't really know all that much about evolutionary theory but something just occurred to me.
For example, of what possible advantage is it to an organism to have a slightly opposable thumb?
Surely it is no advantage, and if so then how could even more opposable thumbed creatures hope to
evolve given that the slightly opposable thumbed creature will be no more successful than its
counterparts?

So surely at least some of the developments we see in organisms must be due to sudden radical
change rather than a gradual process as envisaged by evolution? And this will have the character
more of luck than adaptation. i.e. an organism luckily develops something (through mutation or
whatever) that just happens to be beneficial to it.

Is this at all right?

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I'm afraid the idea that radical, evolutionarily advantageous changes might develop 'by luck' is
extremely weak. As a solution to the problem you have posed, it is a desperate last resort. If there is
going to be any useful explanation, we have to stick with small changes brought about by genetic
mutation. So the challenge is to demonstrate how these small changes — for example, a slightly
opposable thumb — might confer some evolutionary advantage.

Actually, the example you have chosen is not that difficult. The stock examples are the evolution of
the eye, or a bird's wing. We shall come to those in a moment. Let's look at your case. The first point
to make is that an evolutionary advantage can be measured in very small percentages. If a 'slightly
opposed thumb' gives just one tenth of one per cent increase in the chance of successfully
performing a given task, then given the scale that we are working on — thousands of generations,
millions of individuals — that will work its way through. The proportion of individuals with that trait will
increase slowly but inexorably. Then we can run the some process through again, with a further slight
modification, and so on.

Richard Dawkins, in a Royal Academy lecture series for children a few years ago, brilliantly took up
the challenge of the wing and the eye. What good is a tiny fluffy protuberance that might develop into
a wing? Well, an animal that lived in trees might have a fraction of a per cent less chance of dying as
a result of falling out of the tree because the protuberance slightlybreaks its fall, or because it slightly
increases the animal's wind resistance. An eye might first start of as a few slightlylight sensitive cells.
The chance mutation of a narrow ridge of skin around the patch would cast a slightshadow, which
would give the ability to distinguish very crudely between different positions of the light source. You
can work out the rest from there.

As Dawkins graphically described in his lectures, evolutionary theorists have not been content to sit in
armchairs and speculate. The power of computers allows the possibility of constructing detailed,
testable hypotheses. How would a given variation work out after a thousand generations? or ten
thousand? or a hundred thousand? The test can be run through in a few seconds.

When we try to apply these theoretical ideas to the massive complexity of the world of living things,
with or without the aid of computer models, the imagination balks. We are only able to see, to
understand, a very small part of the picture. From that we infer to the whole. It follows that we cannot
provethat the inference is correct. But no theory in science is ever provedonce and for all. The only
claim made is that the theory of evolution by natural selection is, all things considered, the best
explanation.

Geoffrey Klempner