Darwins Theory of Evolution states that the evolution of life underlies processes like selection, reproduction and variation. I think, essentially he says, that the occurences of any ability or property are completely random and the survival of some of them depend on the natural environment and nothing else. I guess this also includes the development of mind or human reason. So human reason may as well not exist at all.
But in his Groundwork for the Metaphysic of Morals Kant says:
We take it as an axiom that in the natural constitution of an organized being (i.e. one suitably adapted to life) no organ will be found that isn’t perfectly adapted to its purpose.
So reason isn’t competent to act as a guide that will lead the will reliably to its objectives and will satisfy all our needs (indeed it adds to our needs!); an implanted instinct would do this job much more reliably. Nevertheless, reason is given to us as a practical faculty, that is, one that is meant to have an influence on the will. Its proper function must be to produce a will that is good in itself and not good as a means.
His argumentation completely relies on an axiom that is incompatible with the Theory of Evolution.
I always understood Kant's ethics to build on nothing but reason, because of his argumentation above.
So to what extent does Darwin's theory argue against Kant's moral philosophy?