All languages are supposed to derive from an ancestral sole language. Or at least they followed some strict grammar rules during their evolution, as synthesized by the Universal Grammar (UG), which made famous in the 1960s Noam Chomsky, MIT professor of linguistics.

Now a vivid debate was started by the work of Daniel L. Everett, a linguist at Illinois State University, who has lived several decades studying Pirahã, the language of a small tribe of 350 indigenous hunter-gatherers in the Amazon rainforest.

But many linguists, including MIT linguistics professor David Pesetsky, disagree with many of Everett's interpretations, both cultural and linguistic, about the Pirahã. "What we tried to do in our response was to highlight the ways in which we are trying to unravel the system that unites all the languages in the world, including Pirahã." said Pesetsky.

Detractors say that the claims about some unique traits to that language can be actually found in other well-documented languages also, such as Bengali and even German. The Universal Grammar changes the focus from philology (the detailed description of individual languages and language families) to the knowledge of the remarkable number of common traits that all languages share, a tool to penetrate inside the human mind.

Everett's 2005 study, "Cultural Constraints on Grammar and Cognition in Pirahã: Another Look at the Design Features of Human Language," described a set of "gaps" in Pirahã morphosyntax (the relationships between words and how their elements convey meaning).

"As a culture, Pirahã speakers lack any sense of the past beyond what living individuals have personally experienced, and they have no creation myths or fiction, no sense of numbers or counting, and no art. Constraints of culture in turn impoverish the language, which has no tenses, no names for colors and other allegedly unique paucities." said Everett.

"The language constraints indicate some of the components of so-called core grammar are subject to cultural constraints, something that is predicted not to occur by Chomsky's universal-grammar model."