A Canadian study, long overlooked, asks “Does a parasite have a better chance of survival if an Inuit or a Mayan spits on it?” Author Ed Shields sent us a copy accompanied by a note saying “Years ago, I chose its provocative title as an attempt to awaken folks to the potential immunochemical importance of salivary glands. I totally failed. It appears that no one read the paper. (Even my mother refused to read it.) Unlike the title, the publication is rather dry (so to speak).” The study is:
“Does a parasite have a better chance of survival if an Inuit or a Mayan spits on it?” Edward D. Shields, Journal of Craniofacial Genetics and Developmental Biology, 1998 Jul-Sep;18(3):171-81.The author, at McGill University, Montreal, Quebec, explains:
“An earlier puzzling observation that the prevalence of a polymorphic male predominate, major salivary gland-associated, static lesion of the mandible increased exponentially from the Arctic to the Tropics was explained by both positive and negative selection (balancing) on major salivary gland endocrine and exocrine factors. Additional prevalence rates presented here identified three high prevalence high-Temperate zone cultures that were unusually exposed to alimentary parasites. A correlation between macroparasite exposure and the mandibular lesion helped refine the potential selective forces that fashioned major salivary gland size variation. The data suggests that positive selection occurred for androgen-induced enlargement of the suite of major salivary glands and consequently increased quantities of factors. Increased quantities of salivary gland biologically active factors enhance innate protection against infestation of macroparasites per se, especially gut parasites. The data further suggests that negative selection against enlarged salivary glands occurred as protection against electrolyte imbalances in electrolyte stressed environments and in females.”
