The first animal to be investigated in this commensal model
approach was the Pacific rat, R. exulans. This small rat was a known
food item throughout the Pacific region. Its natural distribution is
Island Southeast Asia (Tate, 1935) and recently the island of Flores
has been suggested as a likely homeland (Thomson et al., 2014a).
R. exulans remains are found in the earliest archaeological deposits
and middens throughout Polynesia and most of Remote Oceania. It
is a separate species from the later introduced European rats, and
cannot interbreed and generally does not co-exist with them in
European vessels. Therefore, it was argued that the R. exulans
populations found on Pacific islands today should be the direct
descendants of those introduced by the original Pacific colonists
and thus tracing the origins of the rat populations would identify
the origins of the canoes that transported them (Matisoo-Smith,
1994). The model was applied and analyses of mtDNA variation in
Polynesian populations identified multiple origins of rats to both
Hawai'i and New Zealand and indicated that there were two major
spheres of interaction within the Polynesian Triangle, a northern and a southern sphere, both interacting and most likely originating
in Central East Polynesia (the Cook Islands and the Society Islands)
(Matisoo-Smith et al., 1998).