>My understanding is that we have induced innumerable mutations in innumerable
generations of fruit flies, and we find that the results of these breakages in
the genetic material fall within rather clearly defined boundaries. This all
but proves that mutations can not take an organism any which way, but only in
very narrowly defined directions. A mechanical clock can only break in a
certain number of ways. If you wish to substitute the word 'change' for
'break' above, ok. But it is still breaks we are dealing with."<<
I can think of a couple of things which alter the conclusion you draw. First,
radiation acts like an eggbeater for genetic material. This is not completely
analogous to what happens in nature. In nature, the DNA is not broken and
recombined willy nilly all over the place. You have sequence substitutions as
the factor. Radiation does not really make for sequence substitution as often
as merely having two unrelated parts of DNA reconnect.
Secondly, if the nonlinear nature of life is correct, then certain places
within the genome control the development of the morphological form. It is
substitutions within these limited regions that really drive evolution, not
the massive eggscrambling action of irradiated flies.
Third, the innumerable mutations caused by radiation has not been followed by
strong selection in a given direction. No consistent selection for a
particular trait (like a fly that will leave my picnic alone) has been
applied.Thus, no one has been trying to "shape" these flies for the past 50
years.
Dogs have been changed in 10,000 years from the wolf shape to morphological
forms which would be classified as different species if the intervening
animals were extinct. A chihuahua and a St. Bernard are more different than a
lion and a tiger, or cheetah and lion, or lion and puma, morphologically
speaking. However, we know that merely
10,000 years ago St. Bernards and Chihuahuas didn't exist.Where is the limit
with dogs? Oh, yeah, the difference between dogs and the fruit fly is two-fold
A fly, if it is to fly, is limited strictly by the laws of aerodynamics.
The dog does not face such a restriction. Secondly, the dog HAS been
consistently selected over multiple generations for particular tasks and their
anatomy now reflects that selection.
glenn