Passage: Since 1990, other researchers have begun to study and report on the development of this unique language and its community (including Ann Senghas, Marie Coppola, Richard Senghas, Laura Polich, and Jennie Pyers). While each has their own interpretation of the events leading to this language and its development since, all agree that the phenomenon being studied is one of the richest sources of data on language emergence discovered to date.

Question: what is the phenomenon best known for?
richest sources of data on language emergence