If, at present, variation of labor imposes itself after the manner of an overpowering natural law, and with the blindly destructive action of a natural law that meets with obstacles everywhere, large-scale industry through its very catastrophes, makes the recognition of variation of labor and hence of the fitness of the worker for the maximum number of different kinds of labor into a question of life and death. This possibility of varying labor must become a general law of social production, and the existing relations must be adapted to permit its realization in practice. That monstrosity, the disposable working population held in reserve, in misery, for the changing requirements of capitalist exploitation, must be replaced by the individual man who is absolutely available for the different kinds of labor required of him; the partially developed individual, who is merely the bearer of one specialized social function, must be replaced by the totally developed individual, for whom the different social functions are different modes of activity he takes up in turn. (Capital, pg. 618)
This is Marx’s humanism. Is it also the place at which some kind of Darwinian naturalism comes to bear a significant amount of weight in his philosophy of history?