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Re: "Wonderful Life" - repeated. (fwd)



I'm breaking this up into two parts for the sake of length:

>      But he makes phylogenetic history out to be more whimsical
> than it is.  I believe there are in biology, as in physics and
> chemistry, some absolute, if emergent, rules.  And I believe this
> relates to dinosaur extinction.  But first I want to poke some
> holes in Gould's thesis of non-repeatable history.

>      I don't see why mutual symbiosis between these cells would
> not be predicted.  Cells had surely been invading or engulfing
> each other before this fortunate contingency occured.  Symbiosis
> is _everywhere_ in nature.  My own favorite example of the range
> and _inevitability_ of these relationships are the lichen.  Some
> fungi engulf algae and digest them, some set up relationships
> with them.  And there are a number of lichen on a continuum
> between these two extremes.  Gould suggests endosymbiosis was a
> fluke.  But the frequency of these relationships is demonstrable.

     You make some interesting points about unpredictibility in nature.
Howver, as all calculus students and staticians know (and don't forget
chaos theory!), the degree to which you can predict is limited to how far
from your knowledge base you go.  Things get ever more unpredictible the
further you extrapolate.
     For example, covergent evolution implies that there are some designs
that work especially well for certain lifestyles and are more likely
(presumably easier) to develop-BUT within certain animal groups.  The
"Dolphin" design for marine predators is restricted to vertebrates who
head in the water with a long body, backbone, tail, toothy mouth, and limbs
that can be modified into flippers.  However, a jellyfish is a marine predator
that didn't start out with those features, and devolped a very diffenent
anatomy and means of catching, killing, and consuming prey.
     Similarly, if you were looking at prokaryotic cells back in the
Precambrian, you might correctly hypothesize about a symbiotic
relationship developing between different species in the manner that it
did. Howvwer, if you lived a few hundred million years earlier, when only
a few amino acids were floating around in the primordial soup, PERHAPS
you might speculate that some sort of life might evolve, but could you
predict what it would be like, or would it even occur to you that it
would be anatomically capable of such a development?  How abbout if you
went all the way back to when the earth was just a big ball of gas?

LN Jeff
O-