 First, Cohen maintains that, whilst providing “microfoundations”—what he prefers to call “elaborations” of a functional mechanism—would improve a functional explanation, their absence does not necessarily invalidate it. The nineteenth-century Darwinian claim that birds have hollow bones because hollow bones facilitate flight, for example, was already an “excellent” explanation, which was subsequently rendered “even better” through twentieth-century developments in the science of genetics (G. Cohen 1988: 12). Marx’s theory of history might be figuratively located at an analogous position to that not-yet-fully-elaborated Darwinian stage.