The same can be said for macro-evolution. Micro-evolution, or variation,
can be observed and replicated in lab conditions, but macro-evolution
cannot. Many erudite opinions are offered, but no proof.
Trust in the LORD with all your heart,
and do not rely on your own insight.. Pr. 3:5
Ron Chitwood
chitw@flash.net
----------
> From: Derek McLarnen <dmclarne@pcug.org.au>
> To: cliff@noevalley.com
> Cc: evolution@calvin.edu
> Subject: Re: Conspiracy? (was DIFFICULTIES OF DARWINISM 1.4-)
> Date: Sunday, February 22, 1998 5:59 AM
>
> Cliff Lundberg wrote:
>
> > Derek McLarnen wrote:
> >
> > > Stephen Jones wrote:
> >
> > > > Dawkins is right that naturalistic evolution can only
> > > > happen by Neo-Darwinian mechanisms.
> >
> > > A bit simplistic, but essentially right.
> >
> > Since all three of you agree on this, could one of you
> > elaborate a little? What are Neo-Darwinian mechanisms?
> > Which mechanisms are excluded?
>
> What I did after I wrote the following, but should have done
> before, was to read some of your previous correspondence to
> get a feel for your level of knowledge. Consequently, I fear
> that I may have written "below" you. I have not changed it,
> however, since someone else may benefit from the style I
> have used.
>
> Neo-Darwinian evolutionary theory claims that the most
> significant cause of evolution is the adaptation of
> populations of living organisms in response to environmental
> changes. It further claims that adaptation is a result of
> natural selection acting differentially on phenotypically
> distinct members of a population, i.e. individual organisms
> with inherited physical and genetic characteristics that
> allow them to pass on the maximum number of their genes to
> succeeding generations.
>
> Underlying this is the theory that genes exist only to
> replicate. Those genes that are best at replicating
> themselves into succeeding generations will obviously appear
> most frequently in succeeding generations.
>
> Now let's look at the mechanisms, starting at the genetic
> level and working towards the population level.
>
> At the genetic level we are looking for those mechanisms
> that generate genetic diversity. Mutation of genes
> (substitutions, transpositions and insertions of base pairs)
> is the most commonly quoted of these mechanisms but it is
> probably the least frequent to occur. Much more common are
> chromosomal changes (deletion, duplication, inversion and
> translocation of chromosome parts). More common still are
> "crossing-over" events that occur during mitosis and
> meiosis. These serve to shuffle the genetic code into new
> combinations. Occasionally, whole chromosomes will split or
> combine. All of these mechanisms promote genetic variability
> within populations which, in turn, generates the phenotypic
> variability on which natural selection can act.
>
> Natural selection is a higher-level neo-Darwinian mechanism.
> (I have included sexual selection, kin selection and
> species selection in the more general term of natural
> selection. Some may argue that species selection is not
> neo-Darwinian and I don't feel strongly enough about it to
> argue against them.) It is simply that in an enviroment with
> limited resources (almost all natural environments), those
> individual members of a population best able to utilise
> those resources will, on average, live longer, be healthier
> and generate more fertile offspring carrying their genes
> than members of the population less well able to utilise the
> environment's resources.
>
> If the characteristics that enabled the individual to
> utilise its environment's resources are genetically
> inherited rather than environmentally acquired, then those
> characteristics will show up more frequently in succeeding
> generations of the population, simply because, again on
> average, the individuals that have those characteristics
> will pass them on to more offspring.
>
> Other high-level neo-Darwinian mechanisms are allopatric,
> parapatric and sympatric speciation, coevolution and
> extinction. Note that examples of sympatric speciation have,
> as far as I am aware, not yet been found in nature.
>
> Now let's look at some mechanisms that affect evolution but
> are not neo-Darwinian. You should note that, while these
> mechanisms have an enormous impact on the direction and
> tempo of evolution, they are not actually evolutionary
> mechanisms, but the mechanisms that are at work when
> evolution is *not* happening in a population.
>
> Stasis is a good first example since it is so prevalent in
> the fossil record. This is simply evolution at its minimum
> extreme, occuring when there is little or no genotypic or
> phenotypic change in a population. The environment may
> provide practically unlimited resources. The population may
> be maximally adapted to the environment which is stable. The
> population may be less than maximally adapted but the
> genotype changes that would enable it to be better adapted
> have not occurred, or are not possible from the existing
> genotype.
>
> Another non neo-Darwinian mechanism is habitat tracking. The
> standard neo-Darwinian response to a changing environment is
> that the populations inhabiting that environment either
> adapt or go extinct. However, the proponents of punctuated
> equilibria have shown that the most common response to a
> changing environment is that the populations affected simply
> move or spread (if they can) to a nearby environment that
> suits their existing adaptations.
>
> Genetic drift is also arguably not a neo-Darwinian
> mechanism. This is best seen in the comparison between two
> non-interbreeding populations of the same species living in
> very similar environments. It will be noted, over time, that
> the populations will start to vary from each other, not in
> response to environmental imperatives, but simply as a
> result of the accumulation of different random mutations and
> chromosomal changes that, while they may affect appearance,
> do not significantly effect environmental fitness.
>
> All non-Mendelian inheritance mechanisms (including
> Lamarkian inheritance) are not neo-Darwinian, nor are they
> known to occur.
>
> Another mechanism that is not neo-Darwinian, but is
> specifically relevant to this Reflector, is supernatural
> selection. The claim is that a supernatural entity (claimed
> to be "God" among this group, but probably claimed to be
> Allah by a similar Islamic group) is and/or has been
> supernaturally directing evolution to some divine purpose.
> The commonly assumed purpose is usually the creation of
> humankind. This is a hypothesis for which no testable
> supporting evidence has yet been forthcoming, though it
> continues to be widely believed.
>
> There are also a number of supernatural creation hypotheses
> which are neither neo-Darwinian nor even evolutionary, so I
> see no need to describe them further.
>
> What I have written here is incomplete and may not be up to
> date with current thinking. However, your request and my
> response may generate enough additional responses that we
> will both end with a better understanding of what are and
> aren't neo-Darwinian mechanisms.
> --
> Regards
>
> Derek
>
> -----------------------------------------------------
> | Derek McLarnen | dmclarne@pcug.org.au |
> | Melba ACT | derek.mclarnen@telstra.com.au |
> | Australia | |
> -----------------------------------------------------
>
>
>
>