Linguist Daniel Everett spent 40 years studying the Pirahã people of Brazil, originally as a Christian missionary who abandoned his faith after witnessing their remarkable happiness and moral clarity without religious belief. His fieldwork revealed that Pirahã—an isolated language unrelated to any known tongue—lacks recursion, directly contradicting Noam Chomsky's universal theory of language and sparking one of academia's most contentious debates about human cognition and linguistic structure. Everett's fieldwork with the Pirahã disproved Chomsky's claim that all languages require recursion, demonstrating that universally accepted linguistic rules can be challenged by undocumented languages studied through deep, long-term immersion.