RE: Peppered Moths - in black and white (part 2 of 2)

Cliff Lundberg (
Tue, 30 Mar 1999 22:54:55 -0800

Donald Frack wrote:

>Please change your email editor to plain text, if possible.

Sorry, I'm lost in the bells & whistles of a new mail program.

>If you wish to join Grasse, be my guest.

No thanks, but I think he's right in distinguishing between variation
and evolution.

>> Species have ranges of variation, and the environment can, by natural
>> selection, favor a preponderance of a particular variation. When does
>> variation become evolution? I would think the answer is 'when the
>> variation is irreversible.' By this standard, the peppered moth phenomenon
>> is not evolution.

>Well, if you get to define terms to your personal satisfaction, then I guess
>you can define the outcome to suit yourself too. Personally, "when the
>variation is irreversible" does not compute. The only sense I can make out
>of it is that you are talking about speciation. If so, you leave the events
>that lead up to speciation in a separate, and apparently unimportant,
>category. Nearly all biologists would disagree with your separation, and
>its unimportance.

'Speciation' seems a slightly different can of worms. A species' scientific
description includes its range of variation. When that description changes,
evolution has occurred, whether or not the change qualifies as speciation
by whatever standard.

>If you get to define evolution to exclude the study of "variation"
>(population changes?), then demark evolution to exclude variation that is
>"reversible", then, sure, the peppered moth data do not show evolution.
>Under these restrictions, no one except creationists has said they do.

How can variation be evolution? Variation is just bouncing around within
determined limits. Evolution is something beyond this. Evolution is
irreversible; the moth phenomenon is reversible; therefore, the
phenomenon is not an instance of evolution. I don't think I'm making
idiosyncratic definitions here.

Cliff Lundberg ~ San Francisco ~