Re: Evolution, "adaptation", and what's currently adaptive
Gerold Firl (geroldf@sdd.hp.com)
5 Sep 1996 20:23:25 GMT
In article <lpiotrow.403.322D9FE6@magnus.acs.ohio-state.edu>, lpiotrow@magnus.acs.ohio-state.edu (Len Piotrowski) writes:
|> In article <50ieqh$n6l@news.sdd.hp.com> geroldf@sdd.hp.com (Gerold Firl) writes:
|> >Throughout the biosphere
|> >there exists the complete gamut of light-sensing and imaging systems,
|> What makes this "gamut" complete, aside, I know, from the word of Firlmeister?
I say "complete" because it ranges from a very simple ability to sense
light and dark, with no structural "eye" at all, to the sophistication
of humans and raptors, who can discriminate thousands of colors and
extremely fine details, with all the intermediates between.
|> >which maps very well to the developmental evolutionary pathway.
|> Interesting mapping function here: where does this "evolutionary pathway"
|> exist?
In the history of living organisms.
|> > We have
|> >plants which orient their leaves to the sun,
|>
|> ... no eyes!
|>
|> >plankton which can detect
|> >up and down from light and dark,
|>
|> ... no eyes!
|>
|> >and large numbers of independantly
|> >evolved imaging systems ranging from mollusc crude
|>
|> ... no eyes!
|>
|> > to mammalian
|> >sophistication.
|>
|> ... ah, eyed!
Lenny, the next time you're tempted to make a pronouncement on a
subject where you don't know what you're talking about, I hope you'll
remember ... no eyes!
Molluscs do have eyes; indeed, it is one of those contingant facts of
history much beloved by semioticians posing as biologists that the
mollusc eye has some aspects which are intrinsically superior to
vertebrate eyes.
Vertebrate eyes have the retina located behind their capillary net,
which blocks some percentage of the incoming light. Mollusc eyes have
the light sensitive nerve cells in front of the blood vessels. Mollusc
eyes and vertebrate eyes evolved independantly, but it's too late for
us to change; we'll just have to make do with our phylogenetic
constraints.
Now lenny, there's no shame in ignorance; without ignorance, we
couldn't learn - but try not to be so aggressive about it. Aggressive
ignorance looks silly.
|> ? Vision systems continue to evolve *because* of the adaptive benefits that
|> vision accrues? How come a mollusc can't see then?
Some molluscs can't see, just like some vertebrates can't see. Fish
which have lived in underground caves for many generations will lose
their eyes; it isn't worth it for them to make the investment in
growing eyes which are useless anyway.
Now, before you start strumming your teleological harp, lets get this
straight: the genes of the fish do not "know" that they're in a cave,
or that it's dark. What happens is that eventually a mutation occurs
which produces an eyeless fish, and not only does this new
configuration prove to be non-deleterious, it is actually advantageous
- "adaptive", one might even say. It eventually spreads throughout the
entire population. No teleology involved, just random combinations of
genes subjected to natural selection over long periods of time, acted
upon by the competitive environment of differential survival.
|> I have no agenda here, Firl.
You've been coyly cautious about divulging the nature of the chip on
your shoulder, but you clearly have an ax to grind. It seems to have
something to do with the role of "meaning" as it relates to
"meaningful human behavior". For some reason, you object to the idea
that "meaningful human behavior" could be related to an underlying
function. You must hate the ideas of marvin harris. I see you as the
anti-harris.
Have you heard of marvin harris? What do you think of him?
but maybe instead of sniping at others, you should present your own
ideas. Tell me lenny, where does meaning come from? What is the
meaning of meaning? And if meaningful human behavior is not related to
functional adaptations, where does it come from? Why does it exist?
And since humans do function, and they do adapt, how can it be that
their meaningful behavior is unrelated to their functional
adaptations?
|> > if something as obviously
|> >functional as vision didn't evolve as an adaptation, where did it come
|> >from?
|> What it (eyeball) can be used for (to see) says nothing about where it came
|> from. Is this getting too taxing for you, Firl?
Right with you, lenny old boy.
But actually, the use of the eye has a lot to say about where it came
from. The selection pressures which drove the developement of complex
vision systems are patently obvious, and the presence of primitive
eyespots among unicellular organisms shows exactly how the process
began. No mystery, no teleology, the facts are all there for you to
see. Why don't you try asking questions instead tooting your horn?
--
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Disclaimer claims dat de claims claimed in dis are de claims of meself,
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=-=-=-=-=-=-=-=-=-=-=-=-=-=---- Gerold Firl @ ..hplabs!hp-sdd!geroldf
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