[Taxacom] Evolutionary misconceptions (was: Ladderising phylogenetic trees)

[Curtis Clark]

On 3/10/2010 8:16 PM, Kenneth Kinman wrote:
>         What I am talking about is more subtle and debatable---whether
> there is actually a clear distinction between cladogenesis and
> anagenesis (however they are defined) or if there is a continuum of
> types that are really neither one nor the other.

Whether anagenesis (broadly defined) accompanies lineage-splitting is an 
interesting question, but anagenesis within a lineage is clearly 
distinct, because no cladogenesis is happening. I think the only 
confusion is among those who don't think of phenotype shifts 
accompanying cladogenesis as anagenetic.

>          When such reproductive isolation does finally evolve, is it the
> result of cladogenesis or anagenesis?  Or is it really both?  And if you
> are tempted to answer that the cladogenesis came first, can we know how
> much anagenesis had actually previously occurred in the particular
> mainland population which gave rise to the island population.

Cladogenesis is the *result* of genetic isolation (keep in mind that 
allopatry is a kind of genetic isolation, and there has always been the 
debate over whether to count it). If separated populations re-merge, 
there wasn't any claodgenesis.

In that reproductive isolation (*excluding* allopatry in this case) is 
almost always genetic in nature, it would seem to require anagenesis.

>         My point is that the typical cladogram showing the difference
> between anagenesis and cladogenesis is rather simplistic,

No. Cladogenesis is lineage splitting. Anagenesis is genetic/phenotypic 
change within a lineage. Many are confused by that, but the principles 
are straightforward.

> I am doubtful that Laura
> appreciates such subtleties.  She is a psychologist, and I am frankly
> doubtful than even a lot of trained biologists really understand such
> subtle and complex biological concepts.

She does seem to have read the books. I can make statements about 
psychology with which most psychologists will agree, even if I don't 
fully understand the underlying concepts.

>        On the other hand, although some of the students she claims have
> misconceptions may indeed have them (as you noted), but some of the
> students she claims have misconceptions may actually have more insight
> that she has, and in my opinion some of them may far be less subject to
> tautology than she is.

Ken, I've always assumed that you don't have a lot of experience 
teaching. I *aways* wonder whether some of my students don't have more 
insight than I do. But it doesn't matter how much insight a budding 
young scientist has if she's not able to put things in terms of the 
current paradigm.

>        Likewise, I would not assume that all students (especially college
> biology majors) have modern monkeys in mind when they say that apes (and
> thus humans) evolved from "monkeys".

I'll have to disagree on that one. Most biology *graduates* only have a 
conception of a few kinds of modern monkeys, unless they've had courses 
in mammalogy or primatology.

> Perhaps some of them just a have a
> more intuitive understanding that mother-daughter species

There are no mother-daughter species, except arguably from peripatric 
lineage splits. Admittedly, your view of classification leads to 
mother-daughter higher taxa, but that's not the same.

> Criticizing them may be the equivalent of
> criticizing Einstein for disagreeing with students of mere Newtonian
> physics.

Or criticizing Wegener for disagreeing with the geologists of his day. 
But for every Wegener or Einstein, there are dozens of proponents of 
cold fusion, animal magnetism, morgellons, succussion, and many other 
ideas that also resulted from insights (on this list, there is even some 
disagreement as to which group Croizat belongs to).

> In my opinion, stict cladism is in some ways at the Newtonian
> stage (and therefore in some ways less helpful, and perhaps even
> counterproductive).

Of course, Einstein believed in a steady-state universe, and rejected 
quantum uncertainty. Fortunately, science advances through better 
explanations, no matter how dogmatic or persuasive any of us are at any 
given time.

-- 
Curtis Clark                  http://www.csupomona.edu/~jcclark/
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University Web Coordinator, Cal Poly Pomona