Traditional ethnobiological knowledge (tek) in Amazonia can be elucidated by comparative study within a language family. Some of thistek has been more resistant to change than certain elements from other cultural domains, such as kinship and politics. Although muchtek has been nevertheless eroded over time, the Tupí-Guaraní language family shows evidence for retention oftek concerning not only many domesticated and semidomesticated plants but also certain wild resources. In particular, that language family has evidently retained complexes of traits that (1) associate tortoises with the human female reproductive cycle; (2) associate Pachycondyla commutata ants with menarche and female initiation rites; and (3)prescribe the stings of Pseudomyrmex spp. ants as therapy for fever and inflammatory conditions. Such knowledge, however unequally shared in modern languages and cultures, appears to be very old.