Fuller (1997) presents a refutation of the evidence of ancylostomids (hookworms) in the New World. She argues that the life cycle of hookworms limits them to warm, moist environments and, thus, confines their prehistoric distribution to the Old World. Smith (1990) emphasizes that very little is known about the ecological parameters of egg and larval survival and that eggs and larvae can survive in cold environments. Fuller's hookworm life cycle is oversimplistic and does not address the diverse array of infection modes available to Ancylostoma duodenale. This species is capable of mucosal penetration and, therefore, can cause infection if its larvae are eaten. In other words, A. duodenale is a geohelminth, and the host can be an active player in the infection mode.