>On Thu, 30 Nov 95 21:34:10 EST...Stephen Jones said:
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?
Taking similar-sized humans for comparison (so we ignore the effect of
body size), I would be surprised if there wasn't a 10% difference in
teeth size (this would correspond to only a 3% difference per linear
dimension). (Maybe Denis could comment here?) So it isn't necessary to
wait for a mutation; they have already occurred and are floating around
in the gene pool.
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.
The weight increase may be worse because it occurs in the head; this
might affect aerodynamics more than if it was centrally located. Even
if that extra weight only makes the bird feel a little more pooped at
the end of a hard day's flying, that may be the difference between
getting a date vs. remaining a bachelor in the mating season.
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.
No problem. The mutations that cause some humans to have smaller or
larger teeth than normal don't appear to have any harmful effects
either.
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.
No-one said that having smaller teeth would help it lay more eggs, just
that it has a better chance of laying the normal amount.
5. This mutation was not swamped by the rest of the population.
Genes are discrete and don't get "blended out". The Hardy-Weinberg law
says that gene proportions stay constant if no selection is taking place.
6. Some of this bird's offspring also carried the mutation which
caused them to have 0.001% less teeth by weight.
I assume you don't have a problem with this step.
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.
It's not necessary to wait for the first mutation to saturate the
population before having another mutation. There could be many genes
causing smaller than normal teeth, and they could all be increasing in
frequency in parallel.
A good example is the evolution of DDT resistance in insects. There
were a number of ways in which individual bugs could be more resistant
than usual to insecticides, but most bugs would only have one of those
mutations, if they were lucky enough to have any at all. All of those
mechanisms are selected for simultaneously, until we get superbugs which
incorporate most of the previously rare DDT-resistant mutations, and are
far more resistant than any bug which existed prior to DDT usage.
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.
I'm puzzled because you have previously said that you have said that you
have no problem with the idea of teeth disappearing by evolution, and
yet you seem to be trying to show now that it can't occur?
-- Jim Foley Symbios Logic, Fort Collins, COJim.Foley@symbios.com (303) 223-5100 x9765