NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/talk/origins/16871

Internet Message Format | 1993-01-28 | 2.0 KB

Path: sparky!uunet!tdat!tools3!swf
From: [e-mail] (Stan Friesen)
Newsgroups: talk.origins
Subject: Re: Topic for Discussion?
Message-ID: <[e-mail]>
Date: 28 Jan 93 18:35:00 GMT
References: <1jo29o$[e-mail]> <[e-mail]>
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Organization: NCR Teradata Database Business Unit
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In article <[e-mail]>, [e-mail] (James G. Acker) writes:
|>     My own spin on the "macroevolution = cumulative microevolution"
|> question:  the time element is missing.  I think, stressing the "I", that
|> rapid, cumulative microevolution, esp. in those apparently chaotic, turbulent
|> geologic period transitions, does equal macroevolution.  The process
|> occurs too quickly to get a geologic "snapshot" of it in progress, unless,
|> with Archaeopteryx as the ultimate example, we get lucky.

You do not even really need much in the way of chaotic transitions to get this.
All you really need is the founder effects and breeding system disruptions
involved in the formation of small, isolated population on the periphery of
a species range.  Under these conditions normal microevolutionary mechanisms
(selection, drift, mutation pressure &c.) can easily generate considerable
changes in a very short time.  See many of Ernst Mayr's studies on morphological
variation in birds in the East Indies for excellent examples of this.

And, of course, if, as Mayr's model indicates, speciation mostly occurs rapidly
in small,localized areas, it is hardly surprising that this is hardly ever
found in the fossil record.  This conclusion is what is called Punctuated
Equilibrium.  (The irony, of course, is that the very article in which
the P.E. model was proposed there is an example of a case where the local
transitional population *was* preserved - so saying it is 'never' found
is simply not true!)

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