On Fri, 1 Dec 95 11:37:59 MST you wrote:
>On Thu, 30 Nov 95 21:34:10 EST...Stephen Jones said:
SJ>I don't have a problem with the loss of teeth. As a PC I don't
>even have a problem with God developing a bird from a reptilian
>archetype. My problem is understanding how and why this would happen
>according to a *100% naturalistic Darwinian* scenario. Why should a
>bird losing its teeth have a selective advantage over those birds
>which did have teeth?
JF>Isn't there an obvious answer: weight? Not only the weight of the
>teeth themselves, but of the jaw bones need to hold them. Replacing
>all that with a lightweight keratin structure would surely help birds
>fly better (regardless of whether you think it could happen
>naturistically). Ditto for the hollow bones. I won't hazard a guess
>about the other adaptations you mentioned.
The issue is not whether "replacing all that with a lightweight
keratin structure would surely help birds fly better" (of course it
would), but "how and why this would happen according to a *100%
naturalistic Darwinian scenario" as claimed by Dawkins:
"There must be some height, call it h, such that an animal would just
break its neck if it fell from that height, but would just survive if
it fell from a slightly lower height. In this critical zone, any
improvement in the body surface's ability to catch the air and break
the fall, however slight that improvement, can make the difference
between life and death. Natural selection will then favour slight,
prototype wingflaps. When these small wingflaps have become the norm,
the critical height h will become slightly greater. Now a slight
further increase in the wingflaps will make the difference between
life and death. And so on, until we have proper wings." (Dawkins R.,
"The Blind Watchmaker", Penguin: London, 1991, p89)
and
"Five per cent vision is better than no vision at all. Five per cent
hearing is better than no hearing at all. Five per cent flight
efficiency is better than no flight at all. It is thoroughly
believable that every organ or apparatus that we actually see is the
product of a smooth trajectory through animal space, a trajectory in
which every intermediate stage assisted survival and reproduction.
Wherever we have an X in a real live animal, where X is some organ too
complex to have arisen by chance in a single step, then according to
the theory of evolution by natural selection it must be the case that
a fraction of an X is better than no X at all; and two fractions of an
X must be better than one; and a whole X must be better than
nine-tenths of an X. I have no trouble at all in accepting that these
statements are true of eyes, ears including bat ears, wings,
camouflaged and mimicking insects, snake jaws, stings, cuckoo habits
and all the other examples trotted out in anti-evolution propaganda."
(Dawkins R., "The Blind Watchmaker", Penguin: London, 1991, p91)
and
"To 'tame' chance means to break down the very improbable into less
improbable small components arranged in series. No matter how
improbable it is that an X could have arisen from a Y in a single
step, it is always possible to conceive of a series of infinitesimally
graded intermediates between them. However improbable a large-scale
change may be, smaller changes are less improbable. And provided we
postulate a sufficiently large series of sufficiently finely graded
intermediates, we shall be able to derive anything from anything else,
without invoking astronomical improbabilities." (Dawkins R., "The
Blind Watchmaker", Penguin: London, 1991, p317)
As I understand it, what you are saying is that, once upon a time:
1. A bird similar to Archaeopteryx had a genetic mutation in its
sex-cells that caused one of its offspring to be born with less teeth
by weight. Barring a macro-mutation, this would be a very small loss,
say 0.001% of total teeth by weight. This would be probably 0.0001%
of the total bird's weight. In grams it would probably amount to say
0.001% of a gram. Perhaps Denis can give realistic figures for teeth
weight?
2. This tiny loss of weight enabled that bird which had less teeth by
weight to fly slightly faster and higher, say 0.001 of a km/hour or 10
metres higher. This enabled the bird's descendants to eat more food.
This is despite the fact they had less teeth (which previously had
been a selective advantage over no teeth). Or it enabled them to
escape predators. This is despite the birds not having predators in
the air, except other birds.
3. This mutation did not have any other harmful effects, despite
genes normally not acting singly and changes to one gene
usually adversely affecting other parts of the organism.
4. This eating more food/flying faster and higher enabled this bird to
have more offspring. This is despite birds laying the same number of
eggs per mating cycle.
5. This mutation was not swamped by the rest of the population.
6. Some of this bird's offspring also carried the mutation which
caused them to have 0.001% less teeth by weight.
7. Repeat steps 1-6.
8. The bird's descendants with the genetic mutation for 0.001% less
teeth by weight, gradually replaced all the birds in its population
who did not have this mutation.
9. Then one of those birds in 6. above had another genetic mutation
that caused it to lose another 0.001% less teeth by weight.
10. Repeat steps 1-9.
11. Towards the end of this process we have all birds with hardly any
teeth by weight, say only now 0.01 grams total teeth per bird or
0.0001% of the total bird's weight. Yet still the "blind
watchmaker" process works by still giving a slight advantage in flying
faster and higher (and hence leaving more offspring) to those birds
who have the tiniest amount less teeth by weight.
10. Finally the descendants of the bird with the original genetic
mutation that caused it to have to have 0.001% less teeth by weight
have completely replaced those birds that did not have that mutation.
11. At the end of the process, no birds have any teeth at all.
At this stage we have all birds with no teeth and now the
process must start again to evolve a beak using the same Neo-Darwinian
"blind-watchmaker" process.
The non-creationist Denton states:
"To show that any two species of organism are related in an
evolutionary sense, to show for example that one species A, is
ancestral to B, ie A->B or that both species have descended from a
common ancestral source, ie A<->B, it is necessary to satisfy one of
the following conditions. Either one, to find a 'perfect' sequence of
fully functional intermediate forms I1, I2, I3 leading unambiguously
from one species to another, ie A->I1->I2->I3->B, or...two, to
reconstruct hypothetically in great detail the exact sequence of
events which led from A to B or from a common ancestor to A and B,
including thoroughly convincing reconstructions of intermediate forms
and a rigorous and detailed explanation of how and why each stage in
the transformation came about." (Denton M., "Evolution: A Theory in
Crisis", Burnett Books: London, 1985, p55-56).
I am conscious that even eminent Darwinists like Gould do not
necessarily accept these continuous adaptive change stories:
"These tales, in the "just-so story" tradition of evolutionary natural
history, do not prove anything. But the weight of these, and many
similar cases, wore down my faith in gradualism long ago. More
inventive minds may yet save it, but concepts salvaged only by facile
speculation do not appeal much to me." (Gould S.J., "The Return of the
Hopeful Monster", "The Panda's Thumb", Penguin: London, 1980, p158).
I have tried to be fair to the Neo-Darwinism "blind-watchmaker"
process as far as I understand it. I would be happy if it could be
corrected, to clarify its basic thrust. I would accept it if I can be
quite clear in my mind that this "blind watchmaker process" can and
did accomplish unaided the changes outlined above.
Thanks.
Stephen
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