Lawyers.

A woman went to her doctor for advice. She told the physician that her husband had developed a penchant for anal sex, and she wasn't sure it was such a good idea. The Doctor asked, "Do you enjoy it?" She said that she did. He asked, "Does it hurt you?" She said no. The Doctor then told her, "Well, then, there's no reason that you shouldn't practice anal sex, if that's what you like, so long as you take care not to get pregnant." The woman was mystified. She asked, "You can get pregnant from anal sex?" "Of course. Where do you think lawyers come from?"