Board Thread:Wiki Discussion/@comment-24977962-20140524183914/@comment-3492791-20140524184719

I'm guess that since humanity only exists in Dark Souls that you mean that and not Dark Souls 2, but in the future please place your questions in the correct forum.

As to the topic, depending on your progress through the game (which you said is only to Sen's Fortress) you can farm the Undead Rats in the Depths, Baby Skeletons in the Tomb of the Giants, or if you're feeling adventurous the Pisacas in the Duke's Archives.