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BCF related -Reply



Hi!

All this talk of aerofoils and aerodynamics of modern aircraft seems a
little off the mark to me. All modern aircraft are purely powered
gliders (some may argue birds are just flapping gliders of course . .
.). However, the point is birds fly in a totally different way to
aeroplanes - they have a level of control over their flight surfaces a
pilot can only dream of (as indeed I suspect do the gliders in the
animal kingdom). Just watching a bird in flight, even when gliding, it
uses incredible precision movements of its wings, changing their
position in three dimensions in space, adjusting the surface area,
angle of attack etc. etc.

For an animal to go from a non-flying, originally ground dwelling
ancestor to a fully flying (using the special sence that birds fly,
not just passing through air) all intermediate stages must be
advantagous (OR at least NOT dis-advantagous) to the life-style (and
ultimately reprodcutive strategy - a bird of paradise with a huge tail
is far more likely to be predated, but is also many more times likely
to be mated by a female, so individual survivorship only has to go far
enough to produce little ones). To me there are several fundamental
questions:

1) Did feathers derive from reptile like scales (I believe this is
generally accepted). Assuming this then why? What is the advantage of
a slightly more feathery scale over a slightly more scaley scale?

2) If the 'proto-birds' went into the trees why? And why was jumping
out of them an advantage. OK so we take the example (sorry can't
remember who mentioned it) of a predator leaping onto prey from a
great height. What special adaptations would be expected  - a bigger
brain to ensure you hit the target, lighter bones to assist climbing
or heavier ones to ensure you don't get blown off target whilst
dropping, strengthening and butressing to ensure bones don't break on
impact, did feathers evolve before starting to climb or whilst
aboreal, What did this predator eat before it decided to jump etc). 

3) If flight developed from the ground up why? In this case feathers
must have developed first (presumably), so what for? If for insulation
does that mean just a downy coat and then how do the flight feathers
evolve? I could go on!

Either way you look at it a 'miracle' APPEARS to have occured, but
that is true of most living things at first sight.

All of these ideas can then be tested against the fossil  record (poor
as it is at the moment, but getting better all the time), and more
importantly should be thought of in terms of falsification - what
evidence will I accept as DISPROVING this idea (and not then shifting
ground to accomodate the new data should it come in!). 

Lots of questions and not many anwsers, I have my views, but it would
be interesting to see what everybody else comes up with.

Les

Mr Leslie Noe

Centre of Environmental, Earth and Applied Science Research,
School of Environmental and Applied Sciences,
University of Derby,
Kedleston Road,
Derby, DE22 1GB,
England.

e-mail: L.F.Noe@derby.ac.uk