Newsgroups: sci.environment

/ hpindda:sci.environment / gary@ke4zv.uucp (Gary Coffman) /  5:12 am  Apr  1, 1992 /
In article <40911711@hpindda.cup.hp.com> alanm@hpindda.cup.hp.com (Alan McGowen) writes:
>/ hpindda:sci.environment / gary@ke4zv.uucp (Gary Coffman) / 10:14 am  Mar 27, 1992 /
>>
>>Mayr, of course isn't suggesting that evolution involves any sort of
>>forethought.
>>
>>There is little doubt that biological diversity increases with time. Though
>>one would be hard pressed to identify just how our modern fauna is 
>>"superior" to that of the Mesozoic, both rebounded in diversity from
>>extinction crises over a period of tens of millions of years. This suggests
>>that a "direction" -- increasing diversity and complexity -- does exist
>>even if the details are not predictable.
>
>Sure, you could call it almost as certain as increases in enthropy. A 
>feedback mechanism that races to fill a channel with the most disordered 
>noise.

No doubt entropy is increasing in the universe as a whole, but the increase
in biological diversity with time is not an example of increasing biological
disorder. The increasing quantity of biological information on the surface
of the Earth is just the opposite of an entropy increase, as the creationists
delight in pointing out.

>>Other large scale patterns may exist. E.g., highly coevolved, diverse 
>>ecosystems probably use energy more efficently than sparcer, less coevolved 
>>ecosystems do. Thus there are some reasons to think that a kind of ecological
>>"progress" occurs over time as a result of coevolution. Also within lineages,
>>adaptations are refined by natural selection.
>
>I'm not sure I'd say they use energy more efficently as individuals. I
>would agree that biological systems expand to use *as much* of the 
>available energy as possible.

Some evolutionary improvements in energy efficiency -- i.e. physiological
improvments -- do occur, but I was speaking of an increase in the efficiency
of energy use in food webs through the addition of new species. Actually,
physiologies are extremely inefficient by engineering standards, and only
a tiny fraction of the available energy is captured at each step up a food
pyramid. The most basic metabolic pathways were fixed long ago, before
multicellular life existed, and have not changed much since then. Fundamental
changes in the energetics of food webs over time result not from major 
changes in physiology, but the addition of new species to the web.

>>What we do not see is any net tendency for evolution to move towards "good"
>>forms just because they would be "good". Every form that is reached is
>>reached from a neighbor opportunistically. But as diversity increases,
>>so do opportunities. Diversity creates the possibility for new species to
>>appear, which is why it increases with time. It is really more interesting
>>(and difficult) to ask what, if anything, limits the process? The answer
>>may be environmental fluctuation.  I.e. diversity increases until the
>>speciation rate is balanced by the extinction rate due to environmental
>>stochasticity.
>
>Or until a more opportunistic species moves in and disrupts their territory
>as has happened again and again. Rabbits in Australia being one extreme
>example. Kudzu in the South another. Man moving into any ecosystem being 
>yet another. It boils down to the ratio of cooperation to competition in
>the system. The most adaptable species prosper.

Of course these are examples of diversity decreases, not increases. The
assumption that a species that massively disrupts its habitat is necessarily
"more adaptable" is quite naive. Extinctions do occur when geographic barriers
are removed and faunal exchanges occur -- exotic species often do cause a
cascade of extinctions when they are introduced to an ecosystem. But there
is no guarantee that a disruptive species will be present in the final
species composition after the extinctions settle down. 

Humans have wrought unprecedented amounts of damage in a very short time
and will almost certainly wreak very much more in the next century. Only
a fool would equate this with "adaptability" -- it is much more likely
the greatest example of maladaptation in the history of life, a headlong
rush towards extinction. The human "adaptation" would appear to be about
as destructive as any asteroid impact could ever be, and about as foresightful.
Unless that "adaptation" becomes truly a stable coadaptation to the biosphere
almost overnight in evolutionary terms it will not be around much longer.

----------
Alan McGowen

"Whatever you are doing, ask yourself "will the capacity of the world
to support life be diminished by this?" And if the answer is yes, then
don't do it." -- Roger Payne.