I read something interesting on Wikipedia last night, about the development of a certain indigenous Caribbean language:
A few decades prior to the arrival of the first conquistadores, people who spoke a Cariban language expanded into the Lesser Antilles and killed or displaced and also mixed with the Arawak peoples who already inhabited the islands. The resulting language—Kalhíphona or Island Carib—was Carib in name but largely Arawak in substance. This happened because Carib men took Arawak wives, who then passed their language on to the children. For a time, Arawak was spoken by women and children and Carib by adult men, but as each generation of Carib-Arawak boys reached adulthood, they acquired less Carib until only basic vocabulary and a few grammatical elements were left.
However, this whole claim is uncited, and the main page about Island Carib presents a more uncertain and controversial picture, with the possiblity that there never even was an invasion but rather a peaceful assimilation of the Arawaks into Carib identity.