jes1@akgub.UUCP (04/08/87)
Niles Eldredge and Stephen Jay Gould say they have rejected gradualism in favor of what they refer to as "punctuated equilibria." They accept the breaks in the fossil record as being real, reflecting the way evolution is actually recorded in the rocks; they are not merely artifacts of a damaged crust. Eldredge and Gould claim that the record is much better than tradition dictates. They paint a pic- ture of long periods of biological stability punctuated by "rapid" periods of speciation in isolated subpopulations - events we should not expect to find depicted by the fossil remains. We are thus left with the *illusion* of evolutionary jumps and an *undisturbed* ortho- dox chronology. But the two scientists go on to make a revealing confession: *both gradualism and punctuated equilibria are interpre- tations based on preconceived ideas*! All that Eldredge and Gould have done is to contrive an *ad hoc* hypothesis (punctuated equilibria) to explain the lack of fossil evidence while still working within another hypothesis (speciation by natural selection). The former would be an acceptable proposal only if there were other evidence to support the latter - *which there isn't*. By *running gradualism at fast forward*, Eldredge and Gould see the *geological camera* as being unable to record its tracks. They can have their cake and eat it too: the geological record is not so bad after all, and the concept of speciation by natural selec- tion is protected anyway - *even though it still isn't demonstrated*. Incidentally, it would seem that any belief (e.g., specia- tion by natural selection) doggedly maintained after being thorough- ly refuted amounts to a religion. Reference: N. Eldredge & S.J. Gould "Punctuated Equilibria: An Alternative to Phyletic Gradualism" from *Models in Paleobiology* ed. by T.J.M. Schopf (San Francisco 1972), p.91.
jes1@akgub.UUCP (04/08/87)
Previous posting on this subject was by J.E. Strickling.
werner@aecom.UUCP (04/10/87)
In article <829@akgub.UUCP>, jes1@akgub.UUCP (jes1) writes: > Incidentally, it would seem that any belief (e.g., specia- > tion by natural selection) doggedly maintained after being thorough- > ly refuted amounts to a religion. To adapt a line from Winston Churchill, Natural Selection may be the worst theory to explain evolution ever proposed, but it's better than all the others. The fossil record shows an evolving composition, even jes1 admitted that. Given that even opponents of Darwinism have to admit that there was an evolution of species in total (or at least the fossil record thereof), doesn't it make the most sense that new species arose from existing species rather than de-novo. Scientifically, this former hypothesis leads to further questions and further predictions. The contrary theory, continous miraculous conception/ divine intervention leads to no testable theories, in fact denies verification. But such discussion doesn't really belong in sci.bio, although I doubt it will ever be kept out in my lifetime ... -- Craig Werner (MD/PhD '91) !philabs!aecom!werner (1935-14E Eastchester Rd., Bronx NY 10461, 212-931-2517) Everything's different. Nothing's changed. Well, only maybe slightly rearranged.
gallagher@husc4.UUCP (04/10/87)
I've found out in the past 24 hours that there are indeed evolutionary
theories which assign no role or almost no role to natural selection -
so I owe Mr. Strickling an apology.
Specifically, Daniel Brooks and E.O. Wiley ("Evolution as an Entropic
Phenomenon") and Peter Saunders and Mae-wan Ho ("The Complexity of
Organisms" - both in J.W. Pollard, Evolutionary Theory: Paths into the
Future) emphasize that the theory of natural selection, because it is
an optimization theory, is inadequate to explain the complexity of
organisms and the fact that the origin of species and the production
of diversity are time-dependent and thus irreversible phenomena. Hence,
they use the principles of non-equilibrium thermodynamics to model
evolution and embryological development as irreversible entropic
processes characterized by the increase of information complexity.
In this framework, the existence of convergence - which I cited as
proof that natural selection must be a force in evolution - appears
"because variation is constrained by the deterministic factors in the
information systems of organisms" - the same changes appear in
different organisms because these changes correspond to a minimal
increase in complexity...
Along similar lines, Brian Goodwin ("Changing from an evolutionary to
a generative paradigm in biology" in the same book as the above)
argues against the historical emphasis of evolutionary biology. An
adequate answer to the question, "why does this dog have a tail"
is not "because its parents had a tail". He emphasizes morphogenetic
fields - embryological regions which have the ability to generate
forms. Rather than being completely controlled by inherited genetic
elements, they are structures guided by generative principles which
direct spatial and temporal organization. Each morphogenetic field
has the potential of creating a great variety of forms, "because
each morphogenetic field is described by equations with many solutions
which define the set of morphological possibilities." Evolution,
even though it involves changes in genes and the environment, thus
is to be understood as a change from one solution of the morphogenetic
field equations to another.
In both these theories, natural selection is thus entirely peripheral
to the understanding of evolution.
Paul G.