Proposed mechanism underlying Punctuated Equilibrium

[swampfox]

I noticed the thread "Punctuated Equilibria Theories" you guys discussed in 2005, at least the posts I reviewed, did not appear to mention what I have in mind:

To me, Punctuated Equilibrium is beautifully explained by Catastrophe Theory: complex dynamic systems often contain critical points which if reached, cause abrupt and qualitative change to the future dynamics of the system. Viewed from this perspective, evolutionary change is an expression of the underlying dynamics of the biosphere with the actual chemistry and biology serving only as inconsequential trappings.

Consider for example the predator-prey model for a population of fish in a pond. Remove some fish and the population usually adjusts smoothly. However, there is a point, just one more fish, which if removed causes the entire population to die off. That's a critical point.

I believe critical points in the population dynamics of the biosphere are responsible for many of the seemingly abrupt qualitative changes in the evolutionary history of life on earth and feel these have been a major influence in the origin of life, the Cambrian Explosion, Punctuated Equilibrium, and the divergence of man from ape.

Edit: Jesus, 302? I guess I feel I should have reviewed all those post under that thread before I opened my mouth but I don't see a delete button to remove this post.

[Buffy]

Already been proposed by the authors of Punctuated Equilibrium theory, Gould & Eldredge, however it is often confused with the more pure form of Catastrophism which refers mainly to geologic change.

Most of the "debates" in those older threads deal actually with side issues associated with the actual underlying mechanisms of speciation, mostly having to do with the supposed inadequacy of random mutation in being able to drive it without some external force or plan (i.e. a Creator, although that wasn't always stated clearly).

Definitely a facinating topic, and I strongly recommend reading anything (or everything!) by Stephen Jay Gould who brought the topic up in most of his books.

Evolution by Jerks,
Buffy

[swampfox]

Originally Posted by Buffy

Most of the "debates" in those older threads deal actually with side issues associated with the actual underlying mechanisms of speciation, mostly having to do with the supposed inadequacy of random mutation in being able to drive it without some external force or plan (i.e. a Creator, although that wasn't always stated clearly).

Well, the external force is the dynamics in my view expressed best by Rene' Thom in "Structural Stability and Morphogenesis", a book I agree is thick in topology and difficult to follow. He states it this way:

"All creation or destruction of form, or morphogenesis, can be described by the disappearance of the attractors representing the initial forms, and their replacement by capture by the attractors representing the final forms"

Here the attractors (stable morphologies) are similar to the "strange attractors" like the Lorenz and Rossler attractors, and by "capture" he means the dynamics (evolution of that morphology) is perturbed by some event (such as a critical point) into the "basin of attractor" of a new attractor (a new morphology) and so is directed to it (the evolution we observe). In this way, the intrinsic dynamics of the biosphere is expressed in evolutionary change. That's how I interpret his analysis anyway. Could be wrong.

[HydrogenBond]

The critical point sort of makes sense. But it could also be environmentally induced. For example, start with a balance of fish in a tank. I next throw in a big rock to lower the living space, too much food, to much pH up, etc. The environment just created a critical state where once there was none. The new environment has different parameters forcing the eco-system to become critical at a time there was not real bio-need.

The periodic warming and cooling of the earth creates a cyclic critical state in stable eco-systems, requiring evolutionary adaptation that builds on what is already there. If the earth never changed, and progression of life depended only on bio-critical evolution, things would have evolved much slower. Go to a shelter place like the Galapagos and one can still see traces of dinosaurs.

[swampfox]

Originally Posted by HydrogenBond

The critical point sort of makes sense. But it could also be environmentally induced. For example, start with a balance of fish in a tank. I next throw in a big rock to lower the living space, too much food, to much pH up, etc. The environment just created a critical state where once there was none. The new environment has different parameters forcing the eco-system to become critical at a time there was not real bio-need.

H-bond, really when I say dynamics, I mean all factors affecting a species or population or ecosystem in a complex web of interactions controlling its existence: biochemical, genetic history, chance, environmental, and the dynamics of other species. Often though we miss some of the connections; they may be subtle like the wolf population in Yellowstone affecting the aspen trees . . . wolfs don't eat trees. They eat elks though and when we initially removed the wolf population, the elk population rose and ate more of the aspen saplings and (I believe) pushed the dynamics of the aspen past some critical point. Later we brought the wolves back but I don't think the aspen ever recovered (I may not have the story exactly right but I think it's close).