Re: Defining&testing "macroevolution" (was: Testing the Laws of Intelligence)

"Robert Maas, see http://tinyurl.com/uh3t";
<rem642b@xxxxxxxxx> wrote in message
news:rem-2007aug27-001@xxxxxxxxxxxx
From: "mel turner" <mtur...@xxxxxxxxxxxxxxxxxxxxxxx>
As for its meaning, "microevolutionary" seems pretty clear to me:
having to do with microevolution, in other words having to do with
evolution of populations below the level of speciation.

And what is *that* supposed to mean?

It means that changes within a population or within one species is
called "microevolution", as opposed to the origin of new species and
groups of related species from a common ancestral species, which
evolutionary biologists have termed "macroevolution". It's a matter
of scale and convenience, not necessarily any claim that there must be
any different processes involved. I've often stated here that even the
grandest-scale "macroevolution" is merely accumulated "microevolution",
plus the cumulative effects of speciations, plus the cumulative effects
of extinctions of many of the resulting lineages, over longe periods
of time.

How does one decide whether a
given act of evolution (a single mutation, or a single
recombination, or a single death of an individual which changes
population statistics,

It's doubtful those would even qualify as instances of "microevolution",
as evolution is strictly defined.

or a single geologic event which changes the
connectivity between various populations) is or is not "below the
level of speciation"?

Shrug. Do we need our scientific definitions to be such that every
possible case is very easily classified? Many/most biological concepts
will always be a bit fuzzy wrt the real world. What is an "individual",
when looking say at colonial or clonal organisms?

Is there any biologically identifiable sharp point at which an
individual child first becomes an adult?

For example, if all the chromosomes in a plant suddenly double,
making the resultant plants reproductively isolated from all
members of their parent species, is that below the level of
speciation? I'm guessing you'd say no, that's macroevolution
instead.

Speciation by polyploidy [whether autopolyploidy or allopolyploidy]
is indeed a type of rapid "macroevolution" that can happen in a single
generation. Most speciation on the other hand is more of a gradual
'process' than an 'event', and may well often take many thousands of
generations. We can tell that it has happened long after it's finished
happening, but there won't be any identifiable sharp boundary between
"one species" and "two species" while it's still happening. That lack
of precision isn't a problem for our using the word "species" or
"speciation" [or "macroevolution", for that matter].

If a mountain pass becomes impassible, thereby separating two
populations of what was formerly a single species, what about that?

What about it? It may well be the beginning of a "speciation event".
Much later, when the two populations have diverged sufficiently, we
might study them and agree that speciation [and thus, "macroevolution"
by definition] has indeed occurred.

If two populations have 78% cross-fertility, compared to 100% within
either single population, but a mutation in one of the populations
decreases the cross-fertility to only 77%, what about that?

What indeed.
Yes, the speciation process will commonly be very gradual, and there
will always be a broad gray area between "clearly local forms of one
species" and "clearly separate but related species". What of it? Do
you wish to argue that we should therefore completely abandon talking
about "species" and "speciation", since they may be hard to agree on
in every case?

If successive mutations in one or another of the two populations
gradually decrease the cross-fertility from 99% down to less than
one percent, which of the individual mutations is considered to be
the event which crosses the line, no longer "below the level of
speciation"?

Why think there should be any line to cross? Speciation occurs,
whether or not it involves any sharply definable lines. Does this
pose any insurmountable problem for scientific discussions of
speciation and the evolution of higher groups of related species
from common ancestors?

Or is every one of the individual events (except wholescale
chromosome duplication) considered "microevolution", and
"macroevolution" is nothing more than a sufficiently long sequence
of microevolution events?

Whether or not "macroevolution" completely reduces to the cumulative
effects of "microevolution" is indeed a subject of much discussion
among evolutionary biologists, but is still rather irrelevant to my
point here that "microevolution" and "macroevolution" are biological
terms that are actually used by scientists, contrary to your
erroneous claims that they were invalid.

Anyway, the "micro/macro" distinction might still be a convenient
ond based on a difference in scale even if no different processes
at all were involved.

I'm not expecting a concensus definition at this point. I just
expect any *individual*, such as **you**, to precisely define these
terms for your own usage such that it's possible for an external
observer to apply your definitions rigorously to decide each
individual case in a consistent way.

The definition I gave seems consistent enough, with speciation as
the relevant dividing "line" between "microevolution" and
"macroevolution". Is any more precision needed for "macroevolution"
than for "species" or "speciation"?

But the key matter is whether
a million events of microevolution can equal an act of
macroevolution,

It can, but doesn't necessarily have to. Did these million events
of microevolution result in any populations becoming separate
species? That's the criterion.

or whether macroevolution requires some special
kind of event that is all by itself beyond the limits of
microevolution.

There are those who argue that yes, there are some macroevolutionary
processes that don't completely reduce to microevolutionary ones.
Whether they are right or wrong about this, we may still have a
worthwhile distinction based on relative scale.

It might still be practical for people to wish to discuss "History"
and refer to "historical trends", even though it all reduces
completely to the cumulative results of "the day's news", just over
longer periods of time.

You must define your terms, or quote somebody else
who defined them in a way you find acceptable; put up or shut up.

And didn't I link to pages showing how the terms are actually
being used?

Even speciation [= "macroevolution"] can be observed on
timescales much shorter than millions of years.

Until you specify what definition you are using, that statement has
no meaning.

It rather clearly means that speciation can sometimes be observed on
shorter time scales than millions of years. See the t.o. "observed
speciation" FAQs for examples.

Speciation is clearly nothing more than the accumulated
sequence of tiny events.

Except for polyploid speciations, etc? And even if so, so what?
What is your objection?

Is one of those events considered
"macroevolution" all by itself, or is "macroevolution" nothing more
than a large quantity of "microevolution"?

Not necessarily either, of course. Speciation needn't ever be a single
event [again, apart perhaps from polyploid speciations], and lots of
accumulated microevolutionary changes won't count as "macroevolution"
if they don't happen to result in speciation and the branching of
lineages.

If
million*microevolution = macroevolution, then the demonstration of
microevolution, plus the demonstration of deep geological
evolutionary time, is sufficient to prove macroevolution.

The demonstration of microevolutionary change, plus the demonstration
of speciations to give rise to separate but related lineages descended
from a common ancestral species, arguably does go a long way to doing
just that. No other processes seem required.

Could she [Zoe] select for some sort of dramatic changes in her
hypothetical bacteria over a reasonable timescale?
[and thereby demonstrate speciation]

Bacteria don't reproduce sexually,

Well, many do, but in bacterial ways that are quite different
from the typical eukaryotic "sexual reproduction" involving meiosis
and syngamy.

hence they don't have presence
or absence of reproductine isolation (or actually fractional
inter-fertility), hence the term "speciation" has no objective
meaning for bacteria.

Does the term "species" also have no meaning at all for bacteria or
other asexual organisms, or might it merely mean something rather
different from what the word means in sexual organisms? How is it that
bacteriologists have named thousands of separate species of bacteria
[and genera, families, and orders, etc]?

Now if you are willing to precisely define
what you mean by "speciation" per bacteria,

That might seem to hinge on defining "species" of bacteria. You appear
to be denying that any bacterial "species" exist.

maybe we can talk, but
at present what you said above seems to be useless for demonstrating
evolution of bacteria which is not "below the level of speciation".

Shrug, again.
Could we expect to be able to select for rather large differences
among isolated strains of bacteria all descended from a
common-ancestral strain, such that their differences are similar to
or greater than those among different wild bacterial "species", as
they are classified by bacteriologists? I suspect this likely could
be done.

Again, I was disputing that she necessarily needed millions of years
to do what she said she wanted [depending on how much change would
satisfy her].

I understood her to be requiring demonstration that a single
species can split and subsequently diverge to become as different
as chimpanzees and humans are nowadays.

You missed her earlier discussion, then. She had some vague notion of
experimentally "testing natural selection in the context of
macroevolution" using a hypothetical strain of bacteria. AFAIK, the
discussion hadn't yet gotten to the point of determining just how much
change or what sorts of change would satisfy her. You may well be right
that she'll have some unrealistic demands to be shown huge changes that
could never happen in many millions of years, and drawing her out on
this in order to show that her expectations are completely unreasonable
could be worth doing if the discussion were to continue.

Such a transformation
requires millions of years. I understood her *not* to be satisfied
with little bits and pieces of such a transformation which could be
accomplished within a few thousand years, each single bit/piece
demonstrated in a separate clade with merely a hypothesis that over
geological/evolutionary time all the various bits/pieces might
occur within a single clade.

The above's a bit confusing.

AFAIK, she was only talking about breeding for some sort of
"macro" change in a hypothetical strain of bacteria,

Whatever "macro" means in that context has nothing to do with
speciation,

Right, that's why I used "macro" in quotes. No doubt her
"macroevolution" is more like the usual creationist's definition of
"larger changes than I wish to admit occur". Substitute "some sort of
large change" if you prefer.

so why did you even mention the phrase "below the level
of speciation" in this thread??

You can review the discussion if it's unclear to you, but I can
summarize:

Zoe brought in "macroevolution" in the very first sentence of the first
post of this thread. I commented that natural selection is generally
microevolutionary rather than macroevolutionary. You incorrectly
claimed that "microevolutionary" and "microevolutionary" [and perhaps
also "microevolution" and "macroevolution"?] were not valid scientific
terms.

You pretend like you understand what Zoe is requesting,

Don't I? I've had several lengthy discussions with Zoe before; this
one is "like deja vu all over again".

yet you jump around between totally
incompatible interpretations of what she *might* have been talking
about.

Incompatible how?

If she's asking about bacteria, then she can't be talking
about speciation, and vice versa.

So, bacteria don't have any "species"? That's very interesting.

Yes, bacterial "species" aren't necessarily equivalent to the species
of familiar sexually-reproducing organisms, but I can easily imagine
selecting for changes of similar or greater degree to the differences
among "different bacterial species".

I make no pretense of
understanding what Zoe means, nor even claim that Zoe means
anything specific in the first place.

Thus the discussions to draw her out further on her claims and ideas.
It's difficult to achieve, but she sometimes will admit she's mistaken
about something.

As far as I can tell, Zoe is
just throwing out gobbletygook to try to trip up everyone else. You
seem tripped at present.

No, I'm quite comfortably seated.

But would an investigation looking for some sort of impressive result
of long-term strong selection on bacteria need such a long study?
I suppose that depends on what would impress Zoe or other creationists
who might hold out for a change into something that wasn't "still just
a bacterium".

Now you're not just tripping, you've fallen flat on your face.

Why? For suggesting from long experience that creationists might have
ridiculous demands?

The total biomass of "just bacteria" (appx. twenty different phyla)
might be larger than all other biomass put together.

Nevermind biomass, what about their phylogenetic relationships?
The major eubacterial clades are likely much older than any animal
phyla or most other major groups of eukaryotes.

Common descent
driven by mutation + fecundity + natural selection explains all
that diversity (in principle anyway). How does Zoe explain it?

Special creation. If I recall correctly, she's an "old earth, young
life" creationist who wants to deny that evolution and natural
selection can accomplish anything much. Hence this and her previous
thread.

If "microevolution" (of bacteria) means "still just bacteria", then
microevolution is sufficient to explain *all* of that diversity!!

Another fun angle when faced with a "So what? They're still just
insects"-type creationist is to next point out that the origin of
humans from common ancestors with the other apes [or with all other
mammals, or all other metazoan animals, perhaps] must also merely be
"microevolution within a 'kind'" by their same misdefinition of
"microevolution" and their implied criteria for "kinds".

Is Zoe willing to submit on that point?

I envisioned asking her just that if the discussion got that far.

By the same trick of words, evolution of animals results in
"still just animals", so would evolution from primitive sponges
to all the arthropods and chordates and mollusks and thirty other
phyla of animals be considered "microevolution" in the same way?

Strangely enough, creationists rarely even try to answer the question.

Perhaps
you aren't aware that there are documented cases of "speciation"
(what I prefer to call species-splitting, a special case of
lineage-splitting)

I'd say that speciation is very much the same thing as cladogenesis,
and not any special case [other than occurring in the present or
immediate past as opposed to earlier in the history of a lineage].

<http://dictionary.reference.com/search?q=cladogenesis>
evolutionary change by the branching off of new species from common
ancestral types.

It's just a technical term for "lineage-splitting". It's literally
"the origin of clades", if that helps.

If we travel upstream from the lower Mississippi to the upper
MIssissippi or to the Missouri or to the Ohio, are we now in a
"new" river that we weren't in before?? I don't see that the word
"new" has any precise meaning in that definition, so I reject it.

Again with the "precision" confusion. Rivers do indeed fork and/or
join, and evolving lineages do indeed split. Below [earlier than] the
junction [splitting] there is one river [ancestral species]. Above
[later], there are clearly two separate streams [descendant species].
The lack of precision as to which drops of water at the junction
belong to which river [or deciding which pebble was the final "event"
that actually divided them] isn't much of a problem for there clearly
being two "descendant rivers" once we're well past the juncture.

Simply skip the problematic word "new" and replace it with "splitting
of a single ancestral lineage [species] to become separate descendant
lineages [species]",

n. The evolutionary change and diversification resulting from the
branching off of new taxa from common ancestral lineages.
"taxa" (plural of taxon) is a **name**, not a fact of nature.

No, taxa are actually **taxonomic groups**, not names, but I agree
that that's an incorrect definition. Simply put, "cladogenesis" is
exactly the same as your "lineage-splitting".

This
definition seems to say that if we now have two names for the two
sub-populations of what formerly all used the same name, then
something real has happened. Accordingly I reject this definition too.

As you should. You caught them with a pretty bad definition.

I give up. What's your favorite definition of "cladogenesis"?

How about "the origin of clades"? Or, "the splitting of ancestral
lineages to become two or more descendant lineages"?

Besides the relatively few possible known examples of ring species are
the much more numerous cases in the gray area between "clearly forms
of one species" and "clearly separate but related species".

Yes, I agree. The main advantage of a "ring species" over a mere
spread species

"Spread species"?

is that over millions of years the two overlapping
ends of a "ring species" have clearly not interbred sufficiently to
maintain genetic closeness, so we have a clear obvious case where
they are "two different species" as viewed locally. With a non-ring
spread species, the only way to test whether the endpoints can
inter-breed is to conduct breeding experiments, whereby the results
can be disputed as "conditions weren't suitable for breeding due to
scientists using improper procedure, just like when trying to breed
pandas in captivitiy". Not to mention the cost of extensive
breeding experiments to test the hypothesis. Think of ring species
as the "poster child" for transitional forms during speciation
processes.

"Rings" show much the same sort of species-to-species gradual
transitions that are understood to occur during phylogeny, but spread
geographically, among populations all living at the same time instead
of spread over time.

(Speciation isn't an event that suddenly happens. It's a
process that may take hundreds of thousands of years from start to
end.

Right. So much for your desire for great precision with regard to
speciation and macroevolution, then?

It only seems to be an "event" when viewed via the fossil
record where we might have only one clump of fossils every couple
million years along any particular line of descent.)

It just can't be tested in a controlled experiment.

Or, perhaps much of it can on a somewhat smaller scale with organisms
such as bacteria and fruitflies.

If "still just a bacterium" invalidates work with bacteria, then
likewise "still just an insect" invalidates work with fruitflies.

Both of those were merely anticipating the usual creationist
objections [and next we'll get to say that humans and chimps are
both "still just apes"].

With bacteria, species isn't rigorously defined, so you might as
well give up trying to convince a naysayer.

But we might get Zoe or others to admit that the observed changes
are much larger than they had claimed were possible. It's true that
some will likely claim that all bacteria are one "created kind", and
then we can dissect the inconsistencies of this viewpoint with their
idea that natural evolution can't possibly have produced the great
functional/physiological/molecular diversity seen among "just bacteria"

That leaves frultflies
where speciation is well defined yet might occur within the course
of a multi-year but sub-century experiment.

Which I thought was one of the points you disputed?

The question is, what tests does Zoe expect to be made? We can
reasonably expect to be able to show speciation or at least
speciation-in-progress, and to show new adaptations arising by
selection.

Adapations aren't *new*, they're adapted from earlier traits, by
definition.

Well, any adaptive changes will be "new" to the very same extent
that they represent a change. How could it be otherwise?

Demonstration of improved adaptions would simply show
(to Zoe) improvement within a basic kind of trait.

Which seemed to be a large part of what she wanted to deny was
possible in this thread.

I think we need
to go with speciation (species-splitting) processes if we hope to
pin Zoe to the wall and force her to agree to the test criterion
and then present evidence she must either accept or look even
stupider than Behe.

cheers



.

Relevant Pages

  • POTM Post of the Month Nomination: (Re: Defining&testing "macroevolution" (was: Testing the Laws
    ... having to do with microevolution, in other words having to do with ... evolution of populations below the level of speciation. ... populations of what was formerly a single species, ... Bacteria don't reproduce sexually, ...
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  • Defining&testing "macroevolution" (was: Testing the Laws of Intelligence)
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  • Re: New Evolution/ID debate thread
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  • Re: New Evolution / ID debate thread
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  • Re: Bacterial Evolution Question
    ... I would think that it is macro- because the species has changed. ... It's still in the bacteria "kind", and therefore microevolution. ... luck getting them to define "kind", ...
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