>"Macroevolution" is simply a convenient way of indicating that the observed
>changes are large-scale rather than small-scale. The danger with this term
>comes in believing that this is a different kind of evolution, separate from
>and independent of "microevolution".
No, the danger is in dismissing possibilities and in confounding distinct
ideas. You seem determined that macroevolution is really microevolution,
because (a) macroevolution is just a quick series of micro steps, and
(b) any organism formed through macroevolution is just another
organism with microscopic DNA etc underlying its morphology.
Macroevolution is sudden gross change in morphology; the changes at
the cellular/DNA level may or may not be gross. You are stuck on the
notion that evolution must be microevolution, otherwise the creationists
will take over the world. I'm sorry, but the Cambrian explosion looks
like macroevolution; you can't define this away.
>The evidence demonstrates that this is not the case; therefore we could
>just as easily refer to "macoevolutionary" change as large-scale
>evolutionary change. It would say the same thing, but we would also
>recognize that it is still the same kind of basic change as we
>see on a smaller scale as with the peppered moth.
Obviously, macroevolutionary change is large-scale evolutionary change;
we can refer to it that way if it clarifies things. But why must there be
only one "kind of basic change?" If you only mean that micro and macro
both involve DNA, that seems trivial; the interesting part is the phenotype.
>Compared to geological time, nearly all the observed instances of modern-day
>"macroevolution" (such as speciation) are also "instantaneous". Besides,
>the "instantaneous" nature of the Cambrian explosion is an illusion caused
>by the lack of fossil evidence prior to the event.
The 'instanteous' nature of the Cambrian explosion is a fact, shown by the
lack of fossil evidence prior to the event, and the plethora of evidence
after it.
>The recent discovery of fossilized embryoes demonstrates that many of the
>Cambrian forms existed in the Precambrian, side-by-side with the Ediacaran
>fauna, and there is the even more recent announcement of a possible ancestor
>to the Cambrian fauna (Science 283:1919-1923 [3/19/99]). All this indicates
that
>the explosion was not quite so "instantaneous" as the geological timetable
>might lead us to believe.
Not magically instanteous, but too quick for microevolution to suffice.
>However, even if the Cambrian fauna did appear "overnight" geologically
>speaking that would not rule out the fact that these "rapid" large-scale
>changes were caused in part by mutation of duplicated genes (both
>"microevolutionary" mechanisms; the absence of which would make any form of
>"macroevolutionary" change impossible) filtered by natural selection.
I wouldn't say "in part"; I would say these radical steps were all caused by
mutation of genes; Macro and micro both depend on DNA changes. That
doesn't mean all evolution is microevolution at the phenotype level.
>No evolutionist -- not even myself -- has ever claimed that "microevolution"
>[mechanisms] explains it all. What we have said is that "macro-" and
>"microevolution" are all one and the same as evolution as a whole, and that
>the different mechanisms responsible for small-scale and large-scale changes
>are not mutually exclusive or independent, but work cooperatively together.
I wonder what mechanisms you have in mind when you refer to mechanisms
responsible for large-scale changes? Just a succession of micro steps?
You don't claim that 'micro' explains it all, you just say that everything that
isn't micro ultimately is micro? ? I would say micro and macro both are
driven by the same DNA-level mechanisms, but the distinction at the
phenotype level is nevertheless worthwhile.
>Except that as I have pointed out in this post and explained in my previous
>post, this is NOT a valid point, but a tactic invented by creationists to
>attack evolutionary theory. You don't have to take my word for it, Cliff;
>check it out on your own.
Creationists may think they're attacking, but scientists should merely
see it as a challenge to provide a view that reasonable people should
accept. Your science seems driven by reaction to creationists. If you
think supernatural creation is wrong (as I do), why do you care about
creationists? You might dislike the influence creationists might have
on funding or on textbooks, but that has no connection to the science
involved, which is our topic. Science is not political.
Cliff Lundberg ~ San Francisco ~ cliff@noevalley.com