User blog comment:The Bonehead Skipper/Law's Leftovers/@comment-3119203-20120322050527/@comment-3119203-20120322124449

Given that we have seen giants and mermaids, the thought that these creatures are natural seems more likely to me. After all, I don't recall ever seeing Brownbeard's lower body in the manga, and like Levi mentioned on another blog, if Law did it then the animals would still have control over the lower half.