Why is the Yapese language different from many other languages in the Federated States of Micronesia?

The Yapese language is considered distinct from other languages in the Federated States of Micronesia primarily because it is only distantly related to the Nuclear Micronesian languages spoken throughout the rest of the region.1

While Yapese is classified as an Austronesian language, it is categorized as an "aberrant" language because it shares very little vocabulary with more typical languages in its group. Although it is now generally believed to be part of the Oceanic subgroup, its specific placement remains obscure, and it has long been considered unplaceable. Furthermore, the Yapese people themselves are noted for having cultural and linguistic ties that are more closely related to Melanesian traditions than to those of the other Caroline Islands.234