“The Pirahã, Everett wrote, have no numbers, no fixed color terms, no perfect tense, no deep memory, no tradition of art or drawing, and no words for “all,” “each,” “every,” “most,” or “few”—terms of quantification believed by some linguists to be among the common building blocks of human cognition. Everett’s most explosive claim, however, was that Pirahã displays no evidence of recursion, a linguistic operation that consists of inserting one phrase inside another of the same type, as when a speaker combines discrete thoughts (“the man is walking down the street,” “the man is wearing a top hat”) into a single sentence (“The man who is wearing a top hat is walking down the street”). Noam Chomsky, the influential linguistic theorist, has recently revised his theory of universal grammar, arguing that recursion is the cornerstone of all languages, and is possible because of a uniquely human cognitive ability.”
http://www.newyorker.com/magazine/2007/04/16/the-interpreter-2