It seems counting may not be as universal to language as we thought:

The MIT team decided to add a new twist—they started with 10 objects and asked the tribe members to count down. In that experiment, the tribe members used the word previously thought to mean “two” when as many as five or six objects were present, and they used the word for “one” for any quantity between one and four.

This indicates that “these aren’t counting numbers at all,” said Gibson. “They’re signifying relative quantities.”

The Pirahã have become a constant source of interest for researchers studying the nature of language, often upsetting assumptions scholars have held for decades.

A New Yorker piece from last year gives a fuller picture of the controversy and invites one to consider just how much we really understand about the nature of language.