Dear Phil,
before we even start to discuss feathers on birds, it is necessary to understand that evolution does not have a mechanism to go from a simple creature to a bigger, more complex creature, be it from a single celled organism to a Mouse or a Mouse to a Man.
The exquisitely brilliant design and organic technology at work in every living cell on the planet, be it in a Mosquito, a Moth, or a Mouse, or a Man, has no mechanism available to initially create the heritable complex specified information that codes for the structures and processes in that organic technology.
It is nothing more than a ‘faith’ held position that evolution somehow happens.
Natural Selection cannot create.
So, where did all the new specified complex information come from that codes for the new structures and processes in the exquisitely brilliant design and organic technology?
Remember, before we even get as far as Birds and feathers, there is the enormous gap from a single celled self replicating organism to Birds. That gap, in effect means that far more than encyclopaedic quantities of heritable complex specified information has to be written somehow to a quality standard that is unimaginable to most humans like myself.
Random mutations and time are all you have!
You state, “A change is made in the population either for an immediate advantage, or sometimes just random changes occur that have no real benefit” and that is correct, as far as it goes, except that is not evolution of the type of change that sees a single celled organism go through millions of iterations to become a man.
It is merely differential reproduction within a population, i.e., the variation in genetic information across a population, permits those with genetic information more favourable to the current environmental conditions or niche to increase in numbers.
Evolution simplistically claims the origin of species is through some individuals in a population being more suited to prevailing environmental factors such that they increase in numbers within that population over others less suited that correspondingly decrease in numbers within that population, but that IS NOT evolution, again that is merely differential reproduction. A cat is still a cat etc…
Where does the UPHILL INCREASE IN HERITABLE COMPLEX SPECIFIED INFORMATION come from?
Remember, Natural Selection is ruled out as it can only ever select from what is already present in the genome of an organism.
God bless,
jon