In this article we provide a preliminary description and analysis of the most common ergative
constructions in Shawi, a Kawapanan language spoken in Northwestern Amazonia. We offer a
comparison with its sister language, Shiwilu, for which an optional ergativity-marking pattern has
been claimed (Valenzuela, 2008, 2011). There is not enough evidence, however, to claim the exact
same for Shawi. Ergativity in the language is driven by mere syntactic motivations. One of the
most common constituent orders in the language where the ergative marker is obligatory is OAV.
We close the article with a tentative proposal on the passive origins of OAV ergative constructions
in the language, via a by-phrase-like incorporation, and eventual grammaticalisation, resorting
to the formal syntactic theory known as Semantic Syntax (Seuren, 1996).