Mutations ? (Re: D'Abrera on Science and Philosophy)

[Pierre Zagatti]

Neil Jones wrote:
> (snip)
> Religion has never been my opium. I remember as a child of no more than
> six deciding that science gave a better explanation than religious mysticysm.
> (snip)
> I find the arguments of creationists bizzare and very odd.
> A look in talk.origins will reveal a host of Religious "Mentalfundalists"
> spouting spurious arguments such as evolution violating the 2nd law of
> thermodynamics!
> ...

I'm not certain that the problem lies on the old opposition 
creationists/evolutionists. The only argument of creationists 
is the bible, whereas evolution is obvious for everyone 
who opens his eyes. 
I think the mechanisms of evolution are not clear yet.
Basically, spontaneous mutations or genomic recombinations will 
promote a high variability in a population, that will be 
filtered through natural (or sexual) selection.
If we look at a classical mullerian mimicry system, like the
burnet moths (Zygaena) or the genus Heliconius, the whole system
is convincing. As a monophyletic group, the ancestors of all 
species share the same potential of variability/polymorphism. 
A slight genomic change in part of the population will be tested
by natural selection (e.g. bird predation) and development of
a discrete specific mate recognition system may isolate a new 
population without affecting the general protection against
visual predation.
Now if we look at mimicry systems that involve different orders
(bugs-ants or beetles-hornets). It's very difficult to imagine how 
mutations may lead to the mimic habitus, providing that all
intermediates
from the basic bug to the ant-like bug have to be tested through the
filter of natural selection.
Drosophila has been reared in the lab for 100 years. Here we have 3 
generations per month. This means that 3600 generations of Drosophila
have been obtained, and tested, since Morgan. During this period, the
(high level of) mutations observed always led to slight phenotypic
modifications (loss of an enzyme, or de-specialization of an organ).
These are -negative- modifications, which cannot explain how a standart
fly may become a pretty drosophila, nor a basic beetle a hornet-like
Plagionotus. 
Concerning DNA recombinations, I'm not a specialist but it seems
to be a 'black box' explanation without concrete examples of 
-positive- acquisitions.

The lack of positive effects of genomic modifications (observed or
induced in the lab for 100 years) is probably the reason why
so many people are not convinced by the classical approch of
evolution. Now 3600 generations is nothing for organisms that
reached their actual organization at the end of the Cambrian period. 
At the scale of man (one gen. for 20 years, probably less) it means
72,000 years, and we know that the paleolithic man was basically
the same than today.

For my own, I think that these genomic modifications may explain 
the whole process to obtain an ant-like bug. The only difference 
relies on the organisms studied. The animals we study are probably 
stabilized by thousands of centuries of stable strategies, and 
we don't have any 'basic fly' or 'ancestor beetle' in our labs to 
observe the explosive effects of DNA boiling among young organisms.

I've been a little bit wordy, but famous evolutionists explained
this better than I did.

Don't you feel older now ?

-- 
Pierre ZAGATTI
INRA Unite de Phytopharmacie et Mediateurs Chimiques
78026 Versailles Cedex
FRANCE
Tel: (33) 1 30 83 31 18
e-mail zagatti at versailles.inra.fr
http://www.jouy.inra.fr/papillon/