If the flight feather has at least five necessary components, why do you expect me to think it's rational that natural forces with no intention to add functionality came up with mutations, one mutation at a time, to bring the flight feather into fruition? That would be even more miraculous than someone turning water into wine.
Elijah: “Well that is why you look it up. If you did, you would learn that evolution works by steps and that each step has to have some fitness benefit (or at least be neutral). If a modern feather needs 5 different components for flight, then each of those 5 components served a different role in the past.”
Correct me if I’m wrong about the steps evolution would take:
1. featherless birds with featherless wings
2. quilled birds with quilled wings
3. quilled and barbed birds with quilled and barbed wings
4. feathered birds with feathered wings
Four steps doesn’t look overly complicated but the absurdity isn’t diminished. There are many fine details involved:
-superficial layers of fibres, the ultimate size-class in the hierarchy of feather keratin filaments (approx. 6 mm diameter), wound circumferentially round the rachis
-megafibrils
-the medulloid pith comprising gas-filled polyhedral structures
-rachidial fibres (a fibrous composite material, consisting of long fibres (contributing stiffness and strength) bonded by an amorphous matrix
-residual cytosol of keratinocytes housing effete organelles and cytoskeletal elements—all degraded along with corneous envelope
-interdigitating plasma membrane of the original keratinocytes with associated corneous envelope proteins
-three keratin layers comprising circumferential and longitudinal fibres of the cortex and polyhedra of medulloid pith
-smooth muscles that control feather movement
-corpuscles are closely associated with feather follicles and serve primarily as mechanoreceptors that detect subtle ground vibrations and changes in air current
-the calamus is a short, tubular, unpigmented end of the feather, which is rooted in the feather follicle
-the superior umbilicus, a small hole entering the calamus, separate the rachis from the calamus
-two parts of the vane are differentiated: an upper pennaceous portion and a lower plumulaceous portion
-barbules branch from both sides of every barb, and in the pennaceous portion barbules interlock with neighboring barbules to hold the barbs together
-afterfeathers, or hypopennae, are feather-like structure that are attached to the underside of a feather at the superior umbilicus
-feathers are arranged in well-defined tracts
-the size and number of feathers are related to the metabolic rate, temperature, weight, and surface area of the body of that particular species
-the thinness of the skin of birds is one of their unique anatomic adaptations that limits their weight for flight.
-invaginations of the skin form feather follicles.
-the uropygial gland’s oily secretions are spread through the feathers by the bill during preening.
-similar to mammalian keratinocytes, avian keratinocytes undergo keratinization as they move from the basal layer to the outer cornified layer, and they undergo a metamorphosis from a cuboidal to a more squamous form. A unique feature of avian keratinocytes is that they produce large amounts of lipids.
-the lipids produced by the keratinocytes are combined with oils secreted by the uropygial (preen) gland to form a thin film that is deposited over the feathers. This oily film is important for waterproofing feathers, inhibiting bacterial and fungal growth, and preventing feathers from drying out.
-feathers are not permanent structures in a bird; they are shed and replaced on a cyclic basis.
Here’s a classification of feathers:
-filoplumes [ hair-like feathers]
-bristles [stiff, tapered rachis with no barbs]
-powder-down feathers [A whitish talcum-like powder, consisting of keratin granules, is seen on the outer sheaths]
-contour feathers [the largest and the predominant feathers covering a bird’s body]
-down feathers (semiplumes) [a rachis that is shorter than their longest barb]
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