The available documentation is largely due to the efforts of early Catholic missionaries, as summarized by Rivet.
[citation needed] Yameo Masamae (Mazán, Parara) Peba Yagua Čestmír Loukotka (1968), a Czechoslovak linguist, also lists Masamae (Mazán, Parara) as part of the language family.
It is spoken around the Mazán River in Loreto Department, Peru, and is most closely related to Yameo.
There has likely been contact between the Yaguas and Bora–Witotoan peoples, perhaps particularly during the era of the rubber-trade; this may account for some structural similarities between the languages (Doris Payne, linguist, forthcoming).
[citation needed] Jolkesky (2016) notes that there are lexical similarities with the Kwaza, Zaparoan, and Nambikwaran language families due to contact.