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Re: flapping from gliding
From: achut.reddy@Eng.Sun.COM (Achut Reddy)
> The "force of gravity" is a red herring. It pulls downward with the
> same force on _everything_ regardless of whether you are cursorial or
> arboreal, and the same force must be overcome in all cases.
However, the cursorial forma has ALREADY overcome the pull of gravity,
by the mere fact of climbing the tree.
The initial phases of flight thus need not deal with this problem,
and thus need not be as efficient or as powerful.
> BTW, cursorial animals also have to protect themselves from falling
But not to the same degree.
> (remember the recent paper about tripping being fatal for a running
> T. rex?)
Yes. But nobody I know of is suggesting such a *large* animal as
the bird precursor. Falling problems are proportionally greater in
larger animals. A mouse can fall 10 stories and run away, a cat
would probably survive - injured, a human would die of the injuries,
and a horse would make a splash.
It is no accident that most forest gliders are rather larger than
mouse sized. Mice don't really need falling protection.
> Second, there can be other uses for "proto-wings" ...
This is, indeed, the catch.
> For example: insulation,
They would seem to be singularly ineffective as insulation, especially
in the very earliest stages of development, when they are merely slight
ridges on the arms.
> using them as a net to catch prey (Ostrom),
This has always seemd strained and unrealistic to me.
Again, the early stages seem to be ineffective, and the gain, even
in well developed forms, seems to be limited. The *only* animals I
know of to use anything resembling this mechanism of hunting are
insectivorous bats, some of which catch their prey in the uropatagium
(NOT the wing). And in bats the entire hunting strategy is already
so specialized, and so dependent on flight, that I do not see this
as a viable ancestral strategy (jumping to catch flying insects from
the ground is not likely to produce adequate return per calory
> sexual display,
Finally, at least one viable alternative. Even minimal fringes
might be accessible to sexual selection.
> using them as "spoilers" for ground-effects
Again, the gain from this at normally accessible terrestrial speeds
is so minimal compared to the drag generated as to make this unlikely.
> to aid in tight ground maneuvering, using them to gain additional
> height in hopping or jumping, etc.
These, again, require larger than minimal airfoils to be effective,
AND they require a *prior* lifestyle requiring high jumping. The only
flycatchers I know of are themselves fliers.
> None of these require being airborne before the benefits can be
Most require more-than minimal size in the proto-wing, and the
real-world advantage of most is, IMHO, highly doubtful. If jumping
for insects was so good a strategy, there would still be animals using
> BTW, _Exocoetidae_ (flying fish) is another counter-example to
> your gravity argument.
Swimming, by itself, involves counteracting gravity. Swimming ALSO
involves motions similar to those required for flight. (Which is,
in part, why penguins were able to adapt to swimming so well).
In short, a good swimmer, especially one with large fins, is *already*
pre-adapted to a cerain level of aerodynamic capability. Little
additional alteration is needed to go the extra step to flying fish.
Indeed flying fish differ almost entirely in the size of their fins.
> Both are _evolutionarily_ possible.
Well, exept for the sexual selection mode, I find none of your
suggested example to be evolutionarily viable.
To change my mind you will need to come up with an actual *terrestrial*
form that shows the suggested pre-adaptation in its incipient form.
The peace of God be with you.