Re: James Shapiro Article and Neo-Darwinism

Tim Ikeda (
Fri, 11 Sep 1998 23:08:20 -0400

Bob wrote to Loren Haarsma:
> You have hit on an important question: How is evolution to be defined?

Descent with modification. Typically included is the idea that
"natural" mechanisms drive it.

> What is "Neo-Darwinism in the broad sense" to which you refer? Neo-
> Darwinism itself is clearly defined. It is *natural selection*, i. e.,
> genetic variation, with the environment sorting out and selecting the
> most adaptive and reproductively successful phenotypes. It is *Neo*
> because it adds the understanding of genetics initiated by Mendel, with
> the concept of mutations, which was lacking in the vague idea of
> *individual variability* that Darwin utilized, not knowing anything about
> genetics.
> If my definition of Neo-Darwinism is correct, then what do you add to it
> that qualifies as "Neo-Darwinism in the broad sense"? How do you broaden
> it? What is this "entire suite of natural mechanisms" to which you refer?

If your definition of neo-Darwinism is the one being used, then you cannot
"broaden" it in such a way. I see that this is also how Shapiro is using it.
However, in one book, Eldredge and Cracraft present it differently,

"We use the term 'neo-Darwinism' to refer to the body of theory
that identifies mutation as the ultimate source of genetic variation
within populations and states that population sizes are limited and
that there is therefore a resultant pattern of differential re-
production (natural selection) within populations which systematically
alters gene frequencies since only some of the variation present in
one generation can be present in the next. 'Syntheticism' refers to a
loosely defined body of work carried out from the 1920's to the early
1950's, marked especially by a tendency to extrapolate neo-Darwinian
principles to encompass speciational and interspecific evolutionary
phenomena. Thus the terms are not synonyms, as Simpson (ref deleted)
has recently pointed out. To the extent that we accept selection as
the best available deterministic hypothesis accounting for change in
gene content and frequency within populations, we remain neo-Darwinians.
The failure of the synthecists to incorporate speciation theory into a
testable theory of macroevolution leads us to avoid the term in
describing the views presented here."
Niles Eldredge & Joel Cracraft _Phylogenetic patterns and the
evolutionary process: Method and theory in comparative biology_
Columbia University Press, NY 1980 p246. *Typos mine*

Under these guidelines, Shapiro is recognizable as being "anti-synthecist".
Eldredge & Cracraft (and Shapiro & many other biologists) do not think
that selection is the only force at work in evolution. The idea here is
that neo-Darwinism represents one area of influence in the shaping of life
and thus might better seen as one component in evolutionary theory. I do
not know what Loren means by "broadened" but perhaps his thoughts are
similar to what I've presented.

> How do you avoid a "grab-bag definition of evolution, which in the
> end defines nothing?

Caution: Evolution <> neo-Darwinism. Neo-Darwinism does not define
evolution. The "grab-bag" problem properly refers to current definitions
of neo-Darwinism. Evolution can be defined even if all the underlying
mechanisms which give rise to it are not completely understood. One
might also know of all the mechanisms yet still be unable to figure
out what happens when they are thrown together. But that's another issue.

> Would it not be better to give it a new name, such as, "pan-
> evolution" or "change in general" and not tie it to the basic
> Darwinian concept of evolution which, at its core, is natural
> selection?

Perhaps, and I think it happens because people would like to somehow
acknowledge Darwin for his pioneering work.

However, "evolution" alone works just fine for me and I tend to
recognize the difference between that (an event) and neo-Darwinism
(a mechanism).

Natural selection is definitely considered to be one of the drivers
behind change in evolution. However, it is likely that it is not the
only one and may not be the major one in many events leading to
speciation. For example, King and Jukes early on suggested that neutral
drift (another factor in evolutionary change in the genome) could be
considered "non-Darwinian". Self-regulated chromosomal rearrangements
and others such as Shapiro mentions might also be considered non-
Darwinian mechanisms. Some of these details are discussed further
in the PNAS perspectives paper I referenced earlier. They would
however, be considered possible evolutionary mechanisms.

> Thanks for your thoughts on this matter.

Sorry for butting in.

Tim Ikeda ( despam address before use