Local geologists on St. Kitts and Nevis determined that at one point millions of years ago there was a land bridge between the two islands. This means the St. Kitts rodent and the Nevis rodent were once part of the same population. The population was later separated with the collapse of the land bridge that connected St. Kitts and Nevis. A portion of the population of rodents was isolated to each island. The separated portions of the original population each adapted to the island they were isolated on. This event led to the allopatric speciation of the St. Kitts and Nevis rodents.