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Re: Social Evolution - Reply to Rindos
Dave Rindos (arkeo4@UNIWA.UWA.EDU.AU)
Wed, 18 May 1994 09:05:28 +0800
On Tue, 17 May 1994, David L. Carlson wrote:
> Yesterday Read asked
> Rindos to define an evolutionary process. It seems to me that David defined
> "natural selection" as a evolutionary process.
I was more attempting to define the basis for darwinain evolution, in a
brief manner. Selection, note, was the THIRD part of the discussion.
Note also, that selection was a consequence of undirected variation and
heredity.
> I thought that there were
> four basic evolutionary processes: natural selection, genetic drift,
> mutation, and gene flow. Three normally reduce variability, only mutation
> increases variability ("normally" - I know about balanced polymorphism).
Well... by and large, even in genetic evolution, it seems that
recombination is the major means by which selectable variation becomes
generated. This is interesting from the cultural selectionist
perspective since it would appear that recombinations of traits, rather
than the appearance of brand new behaviours, seems to very significant in
our arena of study as well...
> By his definition, domestication of a plant or animal
> is not evolution since it is directed (whether consciously or not).
You missed the point here, methinks. I was talking about *directed*
*variations* arising to solve a problem. In fact, domestication provides
one of the CLEAREST cases imaginable for a darwinian model (do you really
think I would start with something DIFFICULT?? :{) ). The reason for
this is that the genetic changes in the PLANTS were [and remain so, even
despite new highly efficient techinques like genetic engineering] totally
outside of human control. WHile cultural processes could create
environments which would favour new traits in plants, it could not generate
these new traits.
> It seems to me that Rindos definition is too specific for evolutionarr
> processes generally.
> If
> only natural selection produces evolutionary change, what do we call the
> change produced by genetic drift?
>
sampling error. :{)
More seriously, this leads to two points. The minor one, brought up by
Danny, is "do stars evolve?" Sure. And electricity is Power, too.
NOTE: Concepts in science are defined, and understood, in terms of their
theoretical links to causation. Natural selection provides the needed
*causal* framework in which to understand and *explain* evolutionary
processes. Classification of phenomena must always be sensitive to this
aspect of the scientific process. In fact, it is by means of these kinds
of concerns that we can separate "natural" from "artificial" taxonomies.
The "evolution of stars" and the biological evolution conflate into a
totally artifical taxonomy BECAUSE no *causal* theory is held in common in
the two domaines of observation.
Of greater importance in terms of the specific question posed here, we
must consider the matter of "random" events and their role in evolution.
This is a complex business, and hard to spin out quickly in this medium.
When the claim is made that an evolutionary change is due to NON-selected
["random"] processes, such as drift or the closely related founder effect,
what is really being claimed?
Clearly, no claim whatsoever is being made that the change OPPOSES
selective forces. Drift in traits cannot occur if the state being
drifted towards has a lower fitness value at any moment in time. Hence,
minimally, the claim is made that the change in states is evolutionarily
neutral. That no *difference* at the level of causation exists.
Example: In a plant species, over time, the colour of the flower drifts
from white to yellow. However, the plant is bee pollinated and, given the
fact that bee vision responds to different wave-lenghts than people
vision, there has been no change in the appearance of the flowers to the
important agent -- bees. Hence, while WE might say the "colour" has
evolved, it has NOT in terms of the important, causal, forces.
But this leads to another important observation (and it is why neutralism
and random evolution is SO contentious in biology).
What if the change in colour is associated with another trait which DOES
increase overall fitness, such as (to be contemporary) a greater
resistance to acid rain? The mere act of finding such a corrolation will
move the shift in color from "drift" to "selected". Hence, by and large,
neutralistic explanations (while they MAY be true -- sampling error CAN
occur, *especially* in *small* populations), must always lie under a cloud
of uncertainty; sort of a (often temporary) resting place for the "hot
potatoes" of evolution. The problem, ultimately, is empirical, NOT
theoretical.
Of FAR greater significiance (and something which is very easy to forget)
providing an answer of "random" (NOT rejecting the null hypothesis)
actually gives us NO ANSWER! The very word "random" as used in creating a
null hypothesis merely means that the event is unanswerable within the
domaine under consideration. Take the classic business of flipping a coin
-- clearly the appearance of Heads vs Tails is totally deterministically
controlled. IF we could measure (in sufficient detail) the various forces
acting upon that coin we COULD predict the resting state (this is not to
deny that at any given moment there might exist either technical or even
inherent limits to what is measurable!). But all of this gets into issues
of Method and Theory which might be put aside for another time.
Dave
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