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Feathers and flight; BCF



Ronald Orenstein says flight may have evolved for short fluttering flights
between branches.  However, this is not an easy first stage to achieve -
such flights involve take-off, often direction changes, and efficient short
landings with braking - all difficult.  All this does not make for a
feasible first step.

It is worth repeating the central point about first steps in flight.  For
any evolutionary change to take hold, some advantage must be gained, as the
Jehova's witnesses will tell you.  (Genetic drift I think relates more to
random DNA changes without significant phenotype impact.  Archy didn't get
wings through genetic drift!)  Waving your arms about while running will
not give you any extra speed unless you already have feathers/skin flaps
etc.  BUT, long before these have been tuned to effective aerofoil shapes,
AND the bone structure grown and adapted, problems such as the costs of the
extra extra muscle, the feathers getting in the way of the claws and
snagging on things would have been paid for, but most af all, they will
have given DRAG.

However, drag is exactly what you want  when you are falling out of a tree.
 On its own, it can save your life.  Animals of about cat-size or smaller,
if they have sufficient drag, and if they land on their feet on normal
ground, can usually survive a fall from any height, ie at terminal
velocity.  For them in particular, fluffiness of some kind is very likely
indeed to confer evolutionary advantage.  (Consider various tree-top living
monkeys such as colobos (>cats, I know) etc, and maybe some of the smaller
south American ones, and compare with the more ground-dwelling macaques. 
Also compare furry-tailed squirrels with bare-tailed rats, and small-tailed
prairy dogs and chipmunks.)  Evolutionary systems are so short-sighted as
to be blind (although they do have memory).  George Olshevsky will be
expressing this in the next few weeks, probably in a much more beguiling
way, but believe me, any path to vertebrate flight other than
parachute-glide-powered flight is a total non-starter since it does require
far too many evolutionary changes to appear and be co-ordinated all at
once.

On uncinates - they may come and go a bit, but they are more stable than
arm length and the myriad other flight associated features when flight is
lost.

Matthew Troutman says no Enantiform has them; Daren Naish knows of one that
has.  Perhaps he will fill us in on this too.  I wonder if this was the
first of a long line!?

On Toby White's suggestion that the LCA of Troodonts and Dromeos. was
Ornitholestes:  I would suggest that T's and D's are both much birdier than
O.

There is an insulation paradox for evolving from cold to warm bloodied: 
Warm bloods need it, but cold bloods cant's have it.  With birds, I suggest
that the drive towards feathers for parachuting/gliding/flying made warm
bloodedness increasingly feasible in a parallel way.  Notice Squamosia or
whatever it was called had feathers/scales growing out of the top of its
back, in such a way so as not to interfere with sunbathing in sideways
sunshine.   And as for mammals?   Well, how about prickles?

John V Jackson    jjackson@interalpha.co.uk

(Wannabeasaurus   beecee-effia - & proud of it!)