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Re: Punk eq vs gradualism



>Just a little musing on my part over semester break.
>
>One of the biggest debates in evolutionary theory deals with the appropriate=
> model for the evolutionary process.  The traditional view of gradualism=
> states that evolution is a constant process, while the new view of=
> punctuated equalibrium states that evolution occurs in short bursts.  The=
> big question focusing on which model is correct.
>
>What if both views simply describe different aspects of the evolutionary=
> process.  Punk eq covers the realm of what is usually thought when people=
> hear the word "evolution,"  being the process that results in profound=
> changes in a population of animals.  Gradualism would describe the realm of=
> adaptation; in other words, the process that deals with subtle changes in a=
> population.  My point being that since animals are constantly adapting to=
> their environment, gradualism would be the best model for this process.
>
>Therefore, both models are correct.

This is more or less the way that the issue has been settled. Another way
of thinking about it is to consider the scale at which you are looking at
evolutionary change. PE is best supported by palaeontological evidence and
describes the small increments of species-to-species evolution. Gradualism
is supported by biochemical data that looks at evolution over a longer
period and wider phylogenetic scope. PE is a particularly useful marrige of
allopatric speciation models with the temporal aspect of the fossil record.
Gradualism is a better model for analysing genus-to-genus or even higher
level evolutionary change.

What does seem apparent is that gradualism is a poor model for
species-level evolutionary change and, equally, PE is a poor model for
higher-level evolutionary change.

There is, of course, another level in which all evolutionary change is
gradual, even within PE. The "sudden" appearence of a new species in the
fossil record represents the occupation of an area by a daughter species
that evooved gradually in isolation elsewhere.

Cheers, Paul

pwillis@ozemail.com.au