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Author Topic:   Punctuated Equilibria
Chiroptera
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Message 16 of 19 (317105)
06-02-2006 9:41 PM
Reply to: Message 15 by Minnemooseus
06-02-2006 8:57 PM


an interesting diagram
The left hand most picture is what strict phyletic gradualism would predict for a complete fossil record; species evolve continuously, and, if the fossil record were perfect, we would see a nice smooth continuum in morphology in all lineages.
The middle picture is supposed to represent Punctuated Equlibrium. According to that model, speciation events take place quickly (a few tens of thousands of years) in small locations, and so should be largely missing in the fossil record. What we would then see are lots and lots of transitional fossils (the black linettes) with small gaps between them.
The picture on the right represents the creationists incorrect view of the fossil record -- very, very few transitionals with no clear indication of lineages.

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Belfry
Member (Idle past 5163 days)
Posts: 177
From: Ocala, FL
Joined: 11-05-2005


Message 17 of 19 (317110)
06-02-2006 9:56 PM
Reply to: Message 15 by Minnemooseus
06-02-2006 8:57 PM


Re: Bump - A topic revival in search of a good subtitle
I agree, Minnemooseus - I don't think the diagram really captures the difference. That seems to be more about perceptions of the completeness of the fossil record than patterns of PE versus PG.
I'm more accustomed to seeing diagrams like this one (from this site).

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RAZD
Member (Idle past 1482 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 18 of 19 (317120)
06-02-2006 11:06 PM
Reply to: Message 17 by Belfry
06-02-2006 9:56 PM


and common myth-conceptions?
I would think "textbook gradualism" would be represented more by straight lines between known species fossils, for the same amount of change in time, while punkeek would be represented more by a zig-zag line between known species fossils --- IF you need a diagram to represent such development.
I noticed the wikipedia had a whole section on misconceptions"
Punctuated equilibrium - Wikipedia
Punctuated equilibrium is often confused with quantum evolution, saltationism, catastrophism, and with the phenomenon of mass extinction, and is therefore mistakenly thought to oppose the concept of gradualism. It is actually more appropriately understood as a form of gradualism (in the strict and literal sense of biological continuity). This is because even though the changes are considered to be occurring relatively quickly (relative to the species geological existence), changes are still occurring incrementally, with no great changes from one generation to the next.
There is still change in species over time, just at different rates, some better represented in the fossil record than others.

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EZscience
Member (Idle past 5231 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 19 of 19 (317122)
06-02-2006 11:20 PM
Reply to: Message 15 by Minnemooseus
06-02-2006 8:57 PM


Re: Bump - A topic revival in search of a good subtitle
Moose, it would be my interpretation thet the gaps in the lines are intended to represent the periods of change that are indeterminate w/r/t their exact time of occurrance or length of the period of transition.
I think the intent of the diagram is to show only that smooth transtional lines cannot be safely inferred.
I would further comment that the concept of 'punctuated equilibria' is a very useful one for shaking up conventional thought by virtue of the simple fact that it broke a rather iconic assumption that change was happening all around us in all species at *relatively constant rates*, when in fact the rates are very different among taxa and habitats and, most importantly, historical circumstances.

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