It seems absurd to me that Darwin doesn't acknowledge the power that females hold in reproductive scenarios.
Darwin observes that human males are stronger, and often more skilled (among other compliments) and that human females are merely good nurturers. How does the man not see that the only reason males have developed (or even simply displayed) those "superior" characteristics is to impress the females and compete with other males! Within this situation and from an evolutionary standpoint, the females are just as fit and powerful as the males. With the ability to choose a mate based on the "show" that the males put on, the females are equal, if not superior, to males.
Darwin says himself, "In the struggle for survival, the fittest win out at the expense of their rivals because they succeed in adapting themselves best to their environment." In the case of a woman there is no reason to adapt the same qualities as a male because the environment does not demand it of her. Her adaptations will be based on her own reproductive goals and should not be compared so directly to the male's.