Large carnivores that become marauders and man-eaters are frequently thought to be old or infirm, apparently incapable of normal predatory behavior. To evaluate whether this “infirmity theory” offers a general explanation for animal–human conflicts, we examined teeth and jaws of lions (Panthera leo) in museum collections. Although tooth wear and breakage are normal in lions, they are rarely accompanied by severe pathologies. Although the infirmity theory may explain specific instances of carnivore–human conflict, including the infamous case of Tsavo's man-eating lions, most other conflicts can be linked to alternative explanations, especially prey depletion in human-dominated areas, which trigger the opportunity and necessity of exploiting people or livestock (or both) as prey.