F E A T H E R S
1. Down or feathers may have first appeared as head, neck ornament.
Notice that this function still exists.
2. Feathers on arms, near hands of original dinosaur would have been
in the way of arm and head use.
How would feathers develop at these places, then? On the head, it
might make more sense. Or maybe they did not use their heads, arms
-- but then why the claws? They did use the hands.
Did Archeoptreyx' claws develop as a part of flight ( catching on
to something at the end of flight -- since clumsy flier can't land
exactly. (cf. even vultures can miss landings, but not most other
Maybe front claws were for hanging? Unlikely?
Sexual signal with birds -- usually/often elaborate head, neck motion,
plus walking pattern. This most likely preceded vocal signals. Visual
birds are perching birds. Most other types don't use sound. Except
waterfowl, stork, ...?
3. Another factor: how did pre-avian sleep? Long necks stretched?
Of curled back like w. birds? ...there is no point to this...
4. There need be just one reason for introduction of feather -- visual
signaling. Suppose a frill on the head. The movement is amplified
angularly by the length of the frill,. It is at the end of a long
mass (head and neck). These two qualities, plus color and texture
can make such signalling efficient. Once father is established as
a signaller, it can then easily develop as a flight device: under
competitive pressure, location, size and textural qualities all can
evolve in signalling function
5. As for feather as weapon, or tool for catching insects: not very
convincing; there are no animals today that do this. Birds especially
do not exhibit this behavior, whereas they do show the other most
likely original functions of
feathers.
6. Let's suppose the pre-bird is without feather. The new born are
naked. They thermal insulation and protection from rough surfaces,
so the mother lines the stone or wood cradle with soft material. Or
she may construct the nest out of soft material. Now if and when down
first appears on a youngster or newborn, there is already a familiar,
attractive quality to it that in the mother's senses distinguishes
it form the others, It may survive better by its insulation, or may
attract more attention from the parents.(Birds can be very detailed
in lining nests. Rooks make a twig structure, rough at bottom, then
softer twigs, finally, turf filling.)
7. Gradual steps: (all possibilities should be examined!)
Infant chicks -- born with insulating down, then looses it after
an interval.
But one chick doesn't loose the down. If climate changes due to
weather or geographical spread of species, then
the downy chick has an advantage.
Or: downy chick stands out -- noted in Paragraph 6.
Maybe. chick's down is colored different from the body. This is
already a visual signal. As an adult this animal attracts more attention.
Would this novel-looking animal repel others? Maybe, but then new
visual must have developed in a great many of creatures. The correct
rate/size of novelty is probably the answer.
8. Feather as heat regulator -- could be basis of down/feather muscle
action to fluff up or smooth feather, as
birds do it today.
9. Place of or down feather: could have been head, tail, body surface,
(whereas arms and hands are the least likely places for feather of
modern design, but as short structures, down, these could also appear
on arms.
Actually the best basis for feathers appearing on the arms is to
suppose that the whole body becomes covered with short down and the
in further development focuses on competing in signalling efficiency,
and so tending to grow bigger down, and these can be waved in the
air. Cf. emu type of feather!
10. Yes, soft, flowing feathers are the best hypothetical basis for
the source of flying feathers. These soft feathers need only get massive
for a small animal to gain lift by waving the arms. The more massive,
and interlocked the plumage is, even if soft. the more it provides
a lifting surface.
11. Feather on hand could have increased area for striking insects,
or limiting their escape. Knocking them down is
12. Feathers are most likely elements of reptilian scales arranged
in a different structural design.
13. If pre-bird had used feathers on hands, arms for insect catching,
the movement need is forward and down or forward and sideways not
sideways and down, which is the more correct movement for lift. Anyway,
the crucial point is to move the arm down.
14. What movement did pre-birds arms have? A bipedal animal most
likely would have sideways arm-movement to aid in balance.
15. Maybe originally feather on arm grew all around the arm, later
differentially selected for best structuring for
flight.
16. Down could not immediately be used for insulating unless its
density was sufficient. This is a general topic:
The minimum requirement for functioning in a given way.
But as a visual signal, even a sparse spot or two can be functional.
16a. Maybe mammalian hair was originally developed for something
other than body covering for heat insulation: a small patch of hair,
or even less, a strand or two can be functional -- whiskers -- tactile
This is a broader topic: feather/web/hair -- hair most likely
began as sensory apparatus --and hair still performs such functional.
Maybe this can be called "survival" of function. This is also an example
of Bivalence: hair as sensory tool can cover more and more parts of
the body, and at one time it gains two possible functions:
still sensory, but also insulator and also visual signal.
If webbing is still dormant in all vertebrates, it is possible
that nature employs an additive evolving of new structures. In this
case behavior is the same way: seeking cover, roof, tent is the same
in us as it is in rats, squirrels, etc. Why should it not be the same?
On the basis of evidence, nature creates new things only out of old
ones. And something that has been continuously present in the behavior
of most animals (to seek cover) throughout their history is very likely
to exist in humans as an inherited trait. Other examples: ...
RELATED FACTORS
(Size, softness etc.)
G. Rattray Taylor ridicules "pre-adaptation', e.g., of the human tool
grip. But it is exactly that -pre-adapted. (Brachiation, tree living.)
Preadaptaion is really Bivalence -- nature can be tightly packed with
possibilities -- a structure that arises has a given number of possible
functions in another area (usually, but not always, with some (small)
change). Therefore the function seems "pre-adapted".
Size is very important determiner of possible pre-adaptation. In flight
size is of first importance:
* small, light build is ideal and * some form of surface extension-
arising from visual or insulation functions plus flapping. flapping
is arm motion used in activities related to food, competition, aggression,
Why are some living birds born with down, others without it? Which
type represents more closely the pre-avian?
Small birds make soft little nests. Did pre-avian do o likewise? Why
soft? Because soft material is compacted, and provides insulation.
Soft, padded nest -- soft downy chick. There must seem to be a connection
here. Both nest and down on chick insulate it for warmth and for physical
advantages: protection of skin, lubricity in movement (cf. human underarm
furthermore! Soft nest also protects eggs. Sharp contours could puncture
an egg, or at least put concentrated pressure on it. (this egg protection
is valid only to the degree the egg is soft. Bird eggs are all hard,
but reptilian eggs are not so.
Small animal needs efficient signalling system more than a large one.
Consider that today the larger the animal, the less it relies on color
and design to present itself visually. Elephants, whales, apes, bears,
larger fish, and even giraffes are plain colored. But the small ones,
among fish, monkeys, insects, and especially birds are very colorful.
With these creatures visual sense is requisite -- whales, on the other
hand use sound, not sight for communicating because visibility in
water is reduced. Small fish, in close contact are often highly colored.
Therefore, small pre-avian would have good use for visual signalling
far ahead of flight or even "gliding". Small animals need strong signalling
capabilities because even at close distances they are hard to spot
unless they contrast with the background. This is very important for
species, mate recognition.
Signalling by sound is efficient as well, but it is used to cover
distances too great for visual functions or under conditions of poor
visibility. forest dwelling birds, for example, use sound for distant
signalling, and at close range add visual signaling.
Argument for visual display: Bird mating rituals often involve both
parties presenting movements to each other. Both move and interact.
Obviously they are watching each other and they carefully coordinate
their own movements with that of the other one. Therefore a bird has
important function assigned to being noticed, insofar as various body
members move distinctly; information can be transmitted through the
movement of single -- as well as several -- body parts. This permits
supposing that the pre-avian did similar action. Movement of arms
therefore could lead to flight motions, flapping. If visual interaction
was important with pre-avians, then it also support the evolution
of visual functions of body coloring -- a fundamental characteristic
of feathers or any body covering. And the placement of such visual
signals on moving appendages, with much angular amplification of movement,
as on arms or top of head, or on tail would be just as expected. Humans
engage in such activity when they don hats and gloves and shoes, even
socks. Weapon and tool handling involves angular amplification, too.
Another factor to consider: was the pre-avian a ground, rock, bush
or tree-dweller?
Short down in pre-avian could play several roles: 1. Color, shape
of areas as visual signal, 2. enlargement of body, either just adding
to visual size or actively raise by muscles, and 3. just by moving,
rustling in air-movement. What would be the next step in the development
towards flight? Most likely, the flapping of arms as a visual signal.
With the presence of feather/down of correct density and size this
alone can lift the creature off the ground. The distance is not important
because we are only dealing with something like courtship or aggressive
New structures of minimal size are significant in proportion to size
of animal.
Feathers n hands or arms could be used as net and help in limiting
the movement of insects to be caught. But if pre-avian ate things
other the insects? Maybe tiny reptiles. Would this be practical?
Emu and ostrich have lost the ability to fly, but they have kept the
wings and plumage for purposes they are good for: visual sign and
A possible surviving early function of plumage: raising of feathers
(or hair, with mammals) to change, enlarge appearance. This can also
be a factor in developing reptilian side-ways legs to under-the-body
placement. Aside from locomotion, which is possible with splayed legs,
mammalian-type placement obviously enables the animal to increase
its apparent height and size.
Alan Charig in A New Look at Dinosaurs, 1979 says that Archeopteryx
has a running foot, not a perching foot, almost identical with that
of the coelosaur.
Possible stages: small, bipedal pre-avian runner develops down, then
feather as insulation and visual signal. competition causes feather/down
to increase in size. Then in ritual motions arm flapping provides
slight lift. This rising up in the air develops through competition
so the pre-avian can reach increasingly higher. This ability is also
used in acquiring food, escaping from enemies. Claws on hand are important
in catching a hold.
ground dweller -- because short armed, long hind-legged creatures
don not live in trees. Cf. squirrel -- front arms need to be long
Flapping motion of arms -- very useful in visual signalling. feathers
add to surface area. Color and flapping motion significantly visibility.
This is presently exhibited by ground-dwelling and water birds.
Tail may have been an important signal wielder, also.
If insulation is improved by down, then the creature can not only
survive better but can move into colder territories. Insulation can
extend geographical spread.
Important parts of behavior that should be considered: status, sex.
aggression, competition, environment/climate, niche (food, competition),
not just "gliding".
Advance steps toward flight
Small changes on small animals can be functional for "small" purposes.
For example, a tiny ground or tree-dwelling pre-bat (without wing-flaps)
can mutate a small web between the fingers. This increases the surface
area significantly because of the small absolute size of the animal.
Insect catching gains efficiency. When jumping, the small increase
in skin surface area provides more aerial surface, and jumping with
outheld hands promotes gliding. But a small change in visual appearance
is still more effective in functional effect. Tiny things that have
negligible physical effect have large visual one
Even "flying just a bit" can be originally a visual function. In fact
is more likely to be just that. Courtship and aggressive motions of
birds involve repetitious, hinged motions by head, neck, legs and
arms. An arm with enough surface area will lead to lift.
Where did pre-avians live? Plains, deserts, beaches, bushlands, forest.
trees, cliffs, rocks? Even once capable of rudimentary flight such
flying was best as a signal. not as a hunting or escape procedure.
What if pre-avian was a ground-dweller? Then it would run on its long
hind legs. But could also visit trees because its arms would enable
it to hold on. (The front legs of a squirrel are shorter than the
hind legs.) Short arms are useable up in trees because "ground" for
motion is no longer flat, 2-dimensional, but a 3-dimensioanl network.
But then, the small bipedal ancestor of birds would probably not live
in trees, but would run on the ground. So bird flight probably began
on the ground
Birds use fore-arms only for signalling and flying, not for anything
Survivals of earlier, original functions: flapping of wings, rustling
of feathers or down, insulation, increase of apparent size and signaling.
Also a small animal must be able to exhibit and also hide its signalling
device for defensive purpose. Birds can still do this: the wings
open up and fold down.
Wind: this factor is to be considered. Extended surface, either of
down or feather could cause lift simply by being moved by air-pressure.
One can imagine a courting pre-avian stretching out its plumed arms
or tail and being popped up and down by the breeze as part the ritual
Hands or arms with extended surface area can also be used in aggression.
Lizards, like iguanas (in Sundabar, for example) fight rearing up
on hind legs and tail. So a lizard can fight with its hands, standing
on two legs.
If a human being jumps the arms are thrown up by inertia. With pre-avians
with extended arm-surface jumping would initially throw the arms up
and be the first step in flight-motion.
Did pre-avians use their feet for holding, killing prey? Or did they
use their hands for this purpose? How did they sleep?
Best guesses for pre-avian adaptations: *small size, *presence of
down, *Down or feather grows on various parts of body, but only when
on arms, hands OR tail would lift be gained, *running, jumping or
ritual flapping part of behavior.
There was a time when the pre-avian lost the use of its hands \, except
perhaps for use of claws. When would this occur? Hands must have been
used for something else or else they would have become vestigial even
earlier. The pre-avian could have used its hands for handling food
at the mouth, for fighting with claws, for scratching, for balance
in bipedalism.
Origin of arm-flapping: before the time of gliding: as weapon in fighting
and how can an organ or function as signal. After gliding had been
attained flapping would increase gliding distance, and as simple arm
raising to catch a hold on arrival.
What social organization did pre-avians live in ? Groups, herds, families,
individuals? If they lived in groups then they may have had signals
other than mating and aggression, such as warning of danger or its
Feathered, downed arms would provide lift in catching food by jumping.
The arms being used as a reactive force to lift the body would also
lift the body by compressing air underneath them. Down on the arms
would also increase time spent in air, by retarding fall.
Coelosaur, as supposed ancestor of birds -- was small (30 inches
high) with long hind legs and short fore-legs, long fingers and claws.
30 inch size might be far to big for adapting to flight. The smaller
the better. Was it a ground or tree dweller? Short-armed, long-legged
types o not live in trees today. Squirrels do have somewhat short
fore-arms, but these are still proportionately longer than those of
a coelosaur. Squirrels also run a great deal on the ground. Why? Because
walking on two hind feet in trees is not practical, and living in
trees is assisted by long arms, cf. monkeys and apes. As for other
tree-dwelling mammals...(?)
ground-dwelling bipedal or semi-bipedal animals -- ostrich, emu, human,
kangaroo have much longer legs than arms. So the standard tree-dwelling,
glider ancestor of birds refers, if at all, to a late stage of flight
evolution, when the major necessary factors were all in place. Jumping
about in trees is not an immediate pre-construct for flight. It is
far from it. The crucial development is appearance of feather/down
and its location on the body. GENERAL RULES
How can an organ or function evolve when at the initial stage of
development it cannot be used for what later will be its function?
For example, wings? Wings don't appear full-fledged. The answer is
that if the creature is small enough, small developmental growths
can be functionally significant. If the creature is small enough,
a relatively small skin flap at the arm-body junction can offer a
flight surface. A larger animal; would need a considerably larger
increase of surface. This is a well-recognized fact. Size of animals
is rigidly limited by relative mass-\-to-surface ratios. But if a
small appendage or spot appears on a large animal, it can immediately
taken on a visual function. Visual variation in animals is of vast
extent, internal variation is much less.
Bivalence (multipotentiality) can only happen with a creature of relatively
small size. (True??) The potential for a biped is contained in the
quadruped, but can only come forth when the animal is of a certain
maximum size. Small animal needs small changes to become bipedal,
a large one needs larger changes because physics operates differently
according to absolute size. "Proof" of this is the fact that flight
is limited to small animals among the four flying phyla (insect, bird,
fish, mammal).
The rule summarized: *Function-multipotential; *One function= immediately
available; *Second function can develop in peace; *Original function
is built into the new organ or structure that is readily constructible
from existing structures. The notochord feathers, spines...--think
this over more!)
Why did frog evolution stop insofar as major changes go? Maybe once
perfected, they never again possessed any multipotential functions.
Each step in the development of a new function must be accounted for.
Multipotentiality_ human speech: from ape vocalization to infant sound
signalling to human sound and speech making. Human language --, sound
tags with association, rhythm and association (equality, descriptive,
command, that is copulative, adjectival, imperative verbs (In English
Without a significant function structures most often disappear. Or
always? see next paragraph:
webbing -- must be always potentially present. And other covering-tissue
growths like fins on fish and whales and dinosaurs (pelycosaurus,
ichtyosaurus) came about so "predictably". The most likely and most
efficient explanation is that the structuring is still hidden in
the genetic plan. But then if fins are generally not used by phyla
higher than fish, why did this potential not die off? * This subject
has not been explained yet.
Flapping a plane surface produces sound and lift. (insects, birds)
The original function is still present (unchanged, or maybe altered).
The flight of bats and flying mammals is derived from web growth.
Bivalence or multipotential in history of civilization(s):
each generation's psychology is based on status quo, which may rise
in standards of luxury and decline in morals as wealth increases.
An automatic, unavoidable transformation?
Brachiation: The existing mechanism and sensitivity (in controlling
your bodies dynamic movements with your arms, hands and shoulder)
can simply be applied to controlling the dynamic movement of an object
or projectile. In the first case the branch is steady and the body
moves in relation to it, on the second case the body is stationary
while the object changes in relative position to it. As to holding
tools or weapons, that is identical to holding on to branches.
Yawning: whether some intensified breathing or other unknown neural
activity takes place or not, the act of yawning exposes the teeth
or fangs. Maybe those early mammals who showed their fangs often when
they were getting ready to sleep kept communicating last minute reminders
to their mates, reminding them of the fangs or rather the dominance
it signals. The large angle of jaw-movement seen in yawning is does
not improve or amplify the amount or pressure of air exchanged. It
seems mainly to place pressure into certain muscles in the face and
the breathing muscles.
Multipotentiality: A structure develops that has more than one possible
uses. There is then a basis for evolving the second function without
loosing the structure while the second one is still not functional;
This is a statistical matter. Hand and arm articulation is rich in
multipotentiality. Consider that frogs or cockroaches have not evolved
from their near perfect? structure. Perhaps they have not come up
with any multipotentials. Or the environment would not allow one.
Indeed, the environment is an organic part of the potentiality. The
niche, the material, the geography of an animals existence are all
factors. Aesop's fable of a frog fell in a jar of cream is an example
of multipotentiality in the frog's swimming movements and foot-webbing:
just by trashing its legs in the cream churned the cream into butter
and so the frog was able to jump from the jar. Here the environmental
change enabled multipotentiality to act.
SPIDER SILK Another example of
multipotentiality is a spider's silk: silk can be used for making
net, to tie up victim, to execute quick downward movement by dropping
on a line of silk, in spreading baby spiders by air. Here we see another
general rule: immediacy of functional potential. Of the above four
uses of silk, spiders can use only one without having to perform any
other action besides secreting it: dispersal by air. Whether this
was the original function of spider silk is a good question, although
the appearance of silk secretion is itself not a simple development,
and needs other sources its origin. Dispersal by air is a good way
to spread out, but is hardly necessary for the success of the spiders.
There should be a simpler reason for the appearance of silk, and it
should work with only a small amount of silk material. A good function
for the evolution of silk glands would be as an adhesive to attach
eggs to a surface. This happens at a crucial bottle-neck of a spiders
life, and gluing a number eggs takes relatively small amounts of adhesive
substance. The major characteristic of the initially liquid glue must
of course be to dry on contact with air and loose solubility in water.
And this glue be derived from another substance the spider already
secretes: saliva or excretion, or cuticle substance -- arthropod cuticle
grows by a liquid come to the outermost surface through pores, and
there spreading out and drying to insoluble chitinous material.
F R O G S
Frogs have all kinds of special adaptations, even gliding in air,
but they are all basically the same anyway. So are most animals.
?? It can be said that only certain points in a development of a given
species can give rise to a new adaptation leading to a new species
with a new build, etc. because only these loci have multipotentiality.
But these multipotentials are statistically relatively rare. As
for the gliding frog, this one may under the right conditions could
have become the origin of a new type of animal, but because frogs
are not so much reproductively, but developmentally tied to water
this change is not likely. Some tropical frogs' eggs mature in the
air, but the tadpoles fall into water when they emergence. Only if
tadpoles mutated to having air-breathing lungs could frogs enter new
zones of evolutionary potentials. Or perhaps this is not even necessary:
theoretically a frog could evolve into a different animal without
ever leaving the water, perhaps reverting to it for good. Perhaps
the genetic makeup of frogs is not as mutation-prone as that of other
groups? perhaps the combination of frog mutational potentials and
their fundamental biology lacks easy ways to evolve into newer forms.
FLYING FISH The development of
flying fish show a simple sequence of functional multipotential: 1.
fins are rotate in relation to the body; 2. fish jump out of the water
(just by swimming fast enough through the air-water boundary. This
action may be employed in intra-specific communication or in escape;
3. fins have (or can develop through competition to have) sufficient
surface area to hold fish aloft for a while; doing this the fish temporarily
disappears from a predator's or competitor's view and appears at an
unexpected place. On the other hand, in mating behavior, if this is
true? two fish would likely both fly -- check on this!
These thoughts can lead to more general concepts: 1.It is not having
grown the first feather that counts so much as the appearance of genetic
ability , in an individuals makeup, to grow integumental salients
-- things that grow or stick out of the skin or hide. 2. The simplest
explanation may be that later phyla retain older phyletic designs,
however these are as a rule hidden. Nature re-uses, re-designs rather
than creates new design elements. Our tendency to clean ourselves
and our habitations is likely to be the same as that of any animal
that does similar things. What exactly is cleaning? The simplest way
to explain it is to assume some neural-behavioral path where one unit
detects a certain type of information, for example, a contrasting
area in the visual or tactile or odor field (for animals of respective
sensibilities), attached to a certain motor-behavior that removes
this contrasting area from the field. And of course, in humans and
closely allied animals there is also a tension and a resolution feeling
which reinforces the action. That is how the contrast in the field
is felt to be an irritation and its removal brings relief and satisfaction.
Our anger, it has been said, is the same as in reptiles. Of course
we usually have additional effects in our consciousness when we are
angry, it is more the wordless, emotional part of anger, or maybe
even lower, the action part of it, the one that has no thoughts, the
physical gesture that anger can trigger.
Immediate application: A good example occurs in human bipedalism.
This ability has several immediate applications: fighting, especially
among youngsters, hence a role in status determination. Cf. chimp
who dragged cans. Another ability, speech, also functioned as a sex-identifier
and too of attraction. The infant became respondent to voice, the
sexes find each others voices attractive.
The appearance of feather or side vane or skin-webbing is not the
main point. No, what appeared was the genetic potential realized to
grow certain structures. Maybe pre-bats had the potential to grow
webbing while other species, genuses do not?
A basic rules: what is still functional in adaptation that could have
been the original field of adaptation? Traces are enough. !. Adaptation
must have been continuous in functional use. 2>> What possible function
could have been the original one? 3. What setups in adaptation could
lead to the present form of the function?
Multipotentiality: It is not bivalence, but that "things, functions,
happenings" have many sides, points of view to be examined from. "Things,
functions, etc." also have different relationships to different corresponding
"things, functions, etc." = events. So you can't just say, flight
started with gliding. And feathers were originally insulation material.
What exactly happens at each crucial step that we can think of? gliding
and insulation are more than vague statements, they have precise qualities
and requirements, tendencies in the face of other events.
All periods of development must be accounted for: origin, early growth,
later growth. Hence, other theories of flight are incomplete. One
prerequisite -small size. Easy to imagine and it is physically and
dynamically necessary. Two possible/probable origins of feathers are
insulation and inter and intraspecific visual signalling. By the nature
of feather or down construction it is automatically an insulator if
its density is significant. But feather or down is always an excellent
visual datum.
Imagine a (small) dinosaur opening wide its forelimbs and then opening
also a fan of colored feathers.
rule: potential or alternate function can be hidden or present in
another function and it is this "hideousness" that lets the second
function develop until it can take up a role and evolve on its own.
The first function guarantees the survival of the second. To develop
a flying as an escape function is not as neutral a nursery as is
arm-signalling in sexual or competitive
The "Wegener theory" theory
A basic summary: an organ, appendage or other structure may develop
to perform another function. If this structure can intrinsically perform
another different one then this second one may develop and even supplant
the first function. This kind of double potential is inherent in biological,
physical and psychological Nature; natural elements, things that exist
can interact with others in many different relationships. For example,
when water evaporates from leaves, more water is automatically pulled
from the roots. All the tree need do is evaporate through the leaves,
the water uptake occurs automatically. It is better to say that the
water content is a single element which at one end moves out, at the
other one moves into the plant. Obviously, where one thing starts
another one begins is arbitrary.
Flying squirrel, lizard, pterosaur, bats -- how did these get skin
webs between arms and legs? Does skin tend to mutate often? Was there
a bi-valent, multipotential event in place? What basic structure accounts
for webbing? Is there still a segmentation-imitation function in higher
animals, just as in their remote ancestors? Can there still be a tendency
in the building plans to grow side appendages along the sides of the
long axis, corresponding to arms, ribs, legs and other vertebral side-shoots.
Does skin tissue occasionally mutate to grow in new patterns? Or maybe
growing webs between fingers or other joints is still dormant in all
of us animals and can it at times manifest? It is a fact that webbing
between fingers is just one of the unusual developments that 'occurs.
If so, this may be the basis of mammalian flight. All that is needed
is a multipotential development, and flight is achieved by mammals
The exact questions and answers making up the line of reasoning:<**><**>1.
Before anything else, list all possible pre-avian characteristics
pertinent: size. weight, limbs, food, reproduction, competition, niche.<**>2.
How did feather originate? Since feather is not ready-grown what form
at first? Down and filoplume exist today in limited, special cases.
This is too detailed here! To go on: what was the origin of down?
What use could it have had? How was it distributed on the body?<**>3.
How did down develop into feather? What functions, competition could
have done this? <**>4. How could flying arise? Etc.
The course of adaptation leading to flight or any other active function:
<**>1. The physiological basis.<**>2. Must have had continuous existence
and maybe, but not necessarily a conitual functional use. Through
the steps of development there must be a continuity of functional
role.<**>3. The hypothetical original function may still be active.
This would strengthen the argument.<**>4. This continuity must be
accounted for by careful examination of all probable behavioral details
of the evolving organism.