On Mon, 3 Jun 1996 10:22:58 -0400, Bill Hamilton wrote:
BH>In a private response to comments I made on the reflector, Stephen
>Jones challenged my remark to the effect that speciation ought to be
>considered macroevolution. His response was a long quotation from
>Gould, which I confess I haven't read yet.
Here they are for the other Reflectorites to read:
"The strict version, with its emphasis on copious, minute, random
variation molded with excruciating but persistent slowness by natural
selection, also implied that all events of large-scale evolution
(macroevolution) were the gradual, accumulated product of innumerable
steps, each a minute adaptation to changing conditions within a local
population. This "extrapolationist" theory denied any independence
to macroevolution and interpreted all large-scale evolutionary events
(origin of basic designs, long-term trends, patterns of extinction
and faunal turnover) as slowly accumulated microevolution (the study
of small-scale changes within species)." (Gould S.J., "Hen's Teeth
and Horse's Toes", Penguin: London, 1984, p13)
and
"Orthodox neo-Darwinians extrapolate these even and continuous
changes to the most profound structural transitions in the history of
life: by a long series of insensibly graded intermediate steps,
birds are linked to reptiles, fish with jaws to their jawless
ancestors. Macroevolution (major structural transition) is nothing
more than microevolution (flies in bottles) extended. If black moths
can displace white moths in a century, then reptiles can become birds
in a few million years by the smooth and sequential summation of
countless changes. The shift of gene frequencies in local
populations is an adequate model for all evolutionary processes - or
so the current orthodoxy states." (Gould S.J., "The Return of the
Hopeful Monster", "The Panda's Thumb", Penguin: London, 1980, p156).
BH>I have no desire to introduce nonstandard definitions, but my
>question to the group is: How well-established is the distinction
>between micro- and macro-evolution?
If there was no distinction, there would be no need to have two
terms! :-)
BH>My rationale for calling speciation macroevolution was
>that speciation establishes a new population which cannot interbreed with
>an older population. This is an element of irreversibility not present in
>normal genetic variations which do not result in speciation. If there were
>no speciation, it seems to me there would be no macroevolution. Therefore
>it seems reasonable to designate speciation as the elementary, first step
>of macroevolution.
Saying something is "the elementary, first step" of something, does
not make it that something. Eating is "the elementary, first step"
towards gluttony, but it is not gluttony. Drinking is "the
elementary, first step" towards drunkeness, but it is not
drunkenness. The original Darwinist idea was that whole populations
gradually transformed by small-steps (microevolution) into new
species, and ultimately phyla:
"The affinities of all the beings of the same class have sometimes
been represented by a great tree. I believe this simile largely
speaks the truth. The green and budding twigs may represent existing
species; and those produced during former years may represent the
long succession of extinct species. At each period of growth all the
growing twigs have tried to branch out on all sides, and to overtop
and kill the surrounding twigs and branches, in the same manner as
species and groups of species have at all times overmastered other
species in the great battle for life. The limbs divided into great
branches, and these into lesser and lesser branches, were themselves
once, when the tree was young, budding twigs; and this connection of
the former and present buds by ramifying branches may well represent
the classification of all extinct and living species in groups
subordinate to groups. Of the many twigs which flourished when the
tree was a mere bush, only two or three, now grown into great
branches, yet survive and bear the other branches; so with the
species which lived during long-past geological periods, very few
have left living and modified descendants. From the first growth of
the tree, many a limb and branch has decayed and dropped off; and
these fallen branches of various sizes may represent those whole
orders, families, and genera which have now no living
representatives, and which are known to us only in a fossil state.
As we here and there see a thin straggling branch springing from a
fork low down in a tree, and which by some chance has been favoured
and is still alive on its summit, so we occasionally see an animal
like the Ornithorhynchus or Lepidosiren, which in some small degree
connects by its affinities two large branches of life, and which has
apparently been saved from fatal competition by having inhabited a
protected station. As buds give rise by growth to fresh buds, and
these, if vigorous, branch out and overtop on all sides many a
feebler branch, so by generation I believe it has been with the great
Tree of Life, which fills with its dead and broken branches the crust
of the earth, and covers the surface with its ever-branching and
beautiful ramifications." (Darwin C., "The Origin of Species",
Everyman's Library, 1967, J.M. Dent & Sons Ltd, London, p126-127).
This was called phyletic evolution. But the only problem was that
there was no evidence for this is the fossil record:
"The known fossil record fails to document a single example of
phyletic (gradual) evolution accomplishing a major morphologic
transition and hence offers no evidence that the gradualistic model
can be valid." (Stanley, S.M., "Macroevolution", W. H. Freeman and
Co: San Francisco, 1979, p39, in (Denton M., "Evolution: A Theory
in Crisis", Burnett Books: London,1985, p182).
Therefore Gould and Eldredge argued that macroevolution be decoupled
from microevolution and proposed that a higher level process called
"species selection" (a sort of natural selection of whole
species) take the place of mutation and natural selection:
"Macroevolution is decoupled from microevolution, and we must
envision the process governing its course as being analogous to
natural selection but operating at a higher level of organization.
[We would say that it is natural selection, working at a level higher
than the local population.] In this higher-level process species
become analogous to individuals, and speciation replaces
reproduction. The random aspects of speciation take the place of
mutation. Whereas, natural selection operates upon individuals
within populations, a process that can be termed species selection
operates upon species within higher taxa, determining statistical
trends." (Gould S.J. & Eldredge N., "Punctuated equilibria: the
tempo and mode of evolution reconsidered", Paleobiology, 1977, vol.
3, p140)
The only problem is that, as Dawkins has pointed out, species
seelction does not produce any major design changes:
"This is a convenient moment to deal with the hypothesis of species
selection...It is true that the vast majority of species that have
ever lived have gone extinct. It is also true that new species come
into existence at a rate that at least balances the extinction rate,
so that there is a kind of 'species pool' whose composition is
changing all the time. Nonrandom recruitment to the species pool and
nonrandom removal of species from it could, it is true, theoretically
constitute a kind of higher-level natural selection. It is possible
that certain characteristics of species bias their probability of
going extinct, or of budding off new species. The species that we
see in the world will tend to have whatever it takes to come into the
world in the first place - to 'be speciated' - and whatever it takes
not to go extinct. You can call that a form of natural selection if
you wish, although I suspect that it is closer to single-step
selection than to cumulative selection. What I am sceptical about is
the suggestion that this kind of selection has any great importance
in explaining evolution. This may just reflect my biased view of
what is important. As I said at the beginning of this chapter, what
I mainly want a theory of evolution to do is explain complex,
well-designed mechanisms like hearts, hands, eyes and echolocation.
Nobody, not even the most ardent species selectionist, thinks that
species selection can do this." (Dawkins R., "The Blind Watchmaker",
Penguin: London, 1991, p265)
This is the heart of the debate between Gould and Dawkins:
"Dawkins's blind watchmaker model is infinitely preferable to such
oversimplifications, even if it has to make unsupported assumptions
about crucial factors like the frequency of helpful mutations.
Moreover, Dawkins has argued, without serious contradiction as far as
I am aware, that his kind of model is the only naturalistic theory
that can account for biological complexity even in principle. If
rival models of evolution cannot even in principle explain
complexity, Dawkins's blind watchmaker model deserves to be called
the theory of evolution. That is exactly what his protege Helena
Cronin did call it in her book The Ant and the Peacock, where she
referred to the Dawkins model simply as "modern Darwinism."
..By using that term Cronin implicitly relegated all other
understandings of Darwinism to the trash can of history, and for that
she drew a furious reaction from the most famous American advocate of
evolution, Harvard professor Stephen Jay Gould. In his angry review
of Cronin's book, Gould denied that most evolutionary biologists
accept the gene-selection model and declared, for reasons similar to
those I have already discussed, that genes cannot possibly be the
exclusive unit of selection. Gould asserted forcefully that most
important bodily characteristics are "emergent properties" of
organisms which are not produced in any direct way by individual
genes or even combinations of genes. Instead, these properties are
products of such complex interactions among genes that they cannot
even in principle be adequately known or predicted at the genetic
level.
If Gould is correct on that point, then to select for individual
genes or even gene combinations is not to select for predictable
properties in the adult organism. But in that case, how can the
complex adaptations that Dawkins and Cronin seek to explain be built
up by a process of mutation and selection? Gould did not ask himself
that question, nor did he draw his readers' attention to the problem.
Instead he went on to reject what he called the "uniformitarian
vision of extrapolation," which is the fundamental Darwinian
principle illustrated by the finch-beak example with which this
chapter began." (Johnson P.E., "Reason in the Balance", InterVarsity
Press: Downers Grove Ill., 1995, p84)
(Johnson P.E., "Reason in the Balance", InterVarsity Press:
Downers Grove Ill., 1995, p83)
BH>But if I'm out in left field, I would appreciate it if some of you
>experts would let me know.
The "experts" (eg. Gould and Dawkins) have already let us know, by
criticising each others theory and fatally wounding each other.
Dawkins (the zoologist) is right that evolution *must* be by gradual,
step-by-step, tiny stages, otherwise it couldn't happen at all.
Gould (the palaeontologist) is right that the fossil record shows it
didn't happen that way:
"If the fossil record is a reliable guide, "evolution" seems to be a
process in which new forms of life appeared abruptly, remained
fundamentally unchanged throughout their tenure on the earth and
then often became extinct-not because they were gradually
supplanted by improved descendants, but because they were in the
wrong ecological niche at the time of a mass extinction. That is
evolution Gould-style. Because it is derived primarily from
observation, rather than the more abstract theoretical need to
account for complex adaptations, I call it "empirical evolution" to
distinguish it from "blind watchmaker evolution."
The advantage of empirical evolution is that it squares pretty well
with observations. The disadvantage is that it does not explain the
main point that a theory of evolution needs to explain which is the
origin of adaptive complexity. Living organisms are packed with
complex parts that have to work together, and the genetic information
required to keep those parts working properly to serve the needs of
the organism must be enormous. Where did it come from? To stick
with
Dawkins's chosen example, how did the bat get its wings, or its
echolocation (bat sonar) system, or its breathing apparatus, or any
of
the myriad other complex things that bats need to have? Extinctions
might clear the way for surviving organisms to occupy new
environmental niches, but extinction events only kill, they do not
create." (Johnson P.E., "Reason in the Balance", InterVarsity Press:
Downers Grove Ill., 1995, pp86-87)
The answer is that both Gould and Dawkins are right about each
other's theory, that it is wrong! Therefore both Gould and Dawkins
are wrong. The major changes in design of living organisms did not
happen by any naturalistic macroevolutionary process (although
natural processes no doubt were involved). The crucial ingredient
was exogenous intervention by an Intelligent Designer, in short,
Progressive Creation! :-) This is the *only* alternative that fits
the facts.
God bless.
Steve
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