Re: How can we distinguish between "gradual evolution" and "saltation"?

On Aug 1, 2:44 pm, John Harshman <jharshman.diespam...@xxxxxxxxxxx>
wrote:
rev.goetz wrote:
On Jul 31, 10:02 am, John Harshman <jharshman.diespam...@xxxxxxxxxxx>
wrote:

rev.goetz wrote:

On Jul 30, 7:20 pm, John Harshman <jharshman.diespam...@xxxxxxxxxxx>
wrote:

rev.goetz wrote:

How can we distinguish between "gradual evolution" and "saltation"?

In what context? In the fossil record? In a phylogenetic tree? In a lab
experiment? Logically? Your question is not clear.

I will start with Darwin's view of gradualism. I suppose he meant that
all surviving modifications (in regards to the history of descent with
modification) were gradual. And I suppose that he was focusing on
anatomical changes. And in our molecular age, we can apply this to
biochemical systems, which would imply that all surviving step of
biochemical modifications (in the history of descent with
modification) were gradual.

By "gradual", I assume you mean "small" here. A single modification
can't be gradual, since the term applies to rates and requires some kind
of time component.

Yes. "Gradual" implies multiple steps.

Darwin assumed that most variation was small in effect, yes. As Gould
has pointed out, if most variation consists of macromutations (e.g. frog
to prince in one step), then natural selection has little creative
power. The smaller the individual steps, the more natural selection can
be considered as directing evolution's course.

I want to make sure that I understand the term "macromutation". I
assume macromutations have nothing to do with the size of the mutation
such as a point substitution or indel or chromosome aberration, but
the term refers to a major physiological changes such as a major
change in biochemistry or anatomy. So a "micromutation" causes no or
minor changes in physiology while a macromutation causes major changes
in physiology. Is that correct?

It's on the right track. I would say that a macromutation is a mutation
of large effect. It's often been supposed that large effect goes hand in
hand with large genetic change, but this is clearly not the case. And I
have to reject your obsession with physiology, whose definition you
should look up immediately. But yes, more or less.

Here is the defintion that I was implying: "All the functions of a
living organism or any of its parts." And IIRC, one of my genetics
professors would say something to the effect that mutations cause
changes in physiology. And I do not see how I was misusing it. Why do
you think that I am misusing it or is it a matter of taste?


IIRC, Darwin also said something like if the origin of all anatomy
(such as the eye) could not be broken down into small steps of
evolution, then his hypothesis fails. Of course, he was confident that
all anatomical evolution could be broken down into small steps. But
what size steps do you think that Darwin was thought outside of his
theory? And if we translate this neodarwinism, then we may ask, What
magnitude of a macromutation would falsify Darwin's hypothesis of
gradual evolution?

That's a matter of personal taste. I suppose you would put it at
whatever level makes natural selection unimportant as a directing force
in evolution -- at which major evolutionary changes appear in a single
bound, fully formed. And now we have to ask what "major" means. But I
think we could agree that a mutation that turns a patch of
photosensitive cells into a camera eye with lens, retina, pupil, and
intrinsic and extrinsic muscles would be a macromutation, and would turn
natural selection into a minor factor in evolution.

I suppose it is all matter of arbitrary discretion, which can cause
disagreements among scientists.

Well, we already know from comparative biology that such a
macromutation did not occur in eye evolution. But even it it did, then
it would not make natural selection a minor factor in all evolution,
just eye evolution.

I suppose that if there are any cases of "irreducible complexity",
then it would be an issue of how a macromutation caused perhaps
complex molecular tinkering.




Is there any way to test Darwin's view of gradualism in regards to the
history of modifications in anatomy and biochemical systems?

Yes, there are several ways. If you're talking strictly about long-ago
history here, not real-time observation, there are still ways to
estimate the magnitudes of particular changes. We can, for example,
partially reconstruct the history of molecular fixations by mapping them
onto the phylogeny. If nodes are close enough to each other, there will
be only a few differences in any one local region of the genome on any
one branch. And we can try to determine the phenotypic effects of those
changes by experiment.

And of course one can do the same with anatomy, for which the fossil
record can be helpful.


.

Relevant Pages

  • Re: How can we distinguish between "gradual evolution" and "saltation"?
    ... all surviving modifications (in regards to the history of descent with ... minor changes in physiology while a macromutation causes major changes ... I would say that a macromutation is a mutation ... all anatomical evolution could be broken down into small steps. ...
    (talk.origins)
  • Re: How can we distinguish between "gradual evolution" and "saltation"?
    ... all surviving modifications (in regards to the history of descent with ... I want to make sure that I understand the term "macromutation". ... change in biochemistry or anatomy. ... all anatomical evolution could be broken down into small steps. ...
    (talk.origins)
  • Re: How can we distinguish between "gradual evolution" and "saltation"?
    ... all surviving modifications (in regards to the history of descent with ... minor changes in physiology while a macromutation causes major changes ... defining macromutation versus micromutation. ... all anatomical evolution could be broken down into small steps. ...
    (talk.origins)
  • Re: How can we distinguish between "gradual evolution" and "saltation"?
    ... all surviving modifications (in regards to the history of descent with ... minor changes in physiology while a macromutation causes major changes ... all anatomical evolution could be broken down into small steps. ...
    (talk.origins)
  • Re: POTM (was Re: Global Flood)
    ... _Abusing Science_ manages to be readable, ... but they're concerned much more with history than science. ... but once you do you'll get to see evolution ... Alternately, it may involve an ordinary mutation, ...
    (talk.origins)
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