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Re: BAAD BCF



>>First of all there is a prima facie case for ground up right now, flying
>fish. The have developed from my favorite evolutionalry force, "get the hell
>out of the way of the guy that wants to eat me". The fish jumped, and then
>jumped further, then got bigger ventrazl fins and started to glide. and maybe
>wone day the fish will really fly. It just isn't so very hard to explain
>jumping higher and higher and a path to flight. The other things will fall
>into place or maybe some were there to start at the beginning. The tree to
>tree or tree to gound thing seems to produce gliders whereas jumping to
>flight makes more sense as a method to escape.
>
>paul sparks
>

I do not think that the evolution of gliding or flying fishes (and, by the
way, the South American freshwater hatchetfishes (Gasteropelecidae) really
do fly by rapidly flapping their pectoral fins, though they aren't very good
at it) is much guide for similar developments on land.  The biggest
objection to the evolution of wings as escape structures for ground dwellers
is that before they are big enough for real flight, extending them during
running actually produces drag and reduces foot-to-ground contact, resulting
in slowing the animal down, not speeding it up.  To give this up simply to
make a slightly-longer-than-average jump is unlikely to be too useful as an
escape mechanism, unless the prey can literally get out of the way be
clearing an obstacle or reaching a refuge (like a tree, folks!).

 Jumping fishes are doing something quite different - even a short jump may
be confusing to a non-jumping predator and anything that elongates the jump
will be advantageous, so that even a vertical leap without a lateral
component may have some defense function.  Also, the gliding structures are
not extended until the fish completes its power stroke in the jump and has
left the water, so drag is not much of an issue (though needlefish, which
are close relatives of flying fish, leave part of the tail in the water to
give a few extra "kicks") - in fact the example of a hydrofoil or catamaran
may be useful in considering drag for a swimmer.

There is, of course, no evidence that flight evolved to escape predators.
In fact I am inclined to doubt this if only because it seems to have evolved
first in carnivorous forms, leading me to suspect that reaching new sources
of food may have been more important.  A possible exception, megachiropteran
bats, feed on fruit which can only be reached by having access to trees (and
of course fruit did not exist until the Cretaceous).

Even highly-evolved living gliders (which, as I have argued elsewhere on
this list, may not have anything to do with the origin of flight) often use
their gliding ability simply to get about, not just to flee predators; I
have seen this myself in Draco lizards and giant flying squirrels in Borneo.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
Home: 1825 Shady Creek Court                  Messages: (416) 368-4661
Mississauga, Ontario, Canada L5L 3W2          Internet: ornstn@inforamp.net
Office: 130 Adelaide Street W., Suite 1940    
Toronto, Ontario Canada M5H 3P5