I'd be grateful if the anti-Darwin folks around here would tell the whole story. From Chapter 5 of Descent:
The aid which we feel impelled to give to the helpless is mainly an incidental result of the instinct of sympathy, which was originally acquired as part of the social instincts, but subsequently rendered, in the manner previously indicated, more tender and more widely diffused. Nor could we check our sympathy, even at the urging of hard reason, without deterioration in the noblest part of our nature. The surgeon may harden himself whilst performing an operation, for he knows that he is acting for the good of his patient; but if we were intentionally to neglect the weak and helpless, it could only be for a contingent benefit, with an overwhelming present evil. We must therefore bear the undoubtedly bad effects of the weak surviving and propagating their kind ...
Why are you lost? You posted something about Darwin's attitude toward human reproduction. I posted the context of it for the benefit of those who may be interested in Darwin's attitude toward reproduction, birth-control, etc. What's confusing you?