 There is evidence that ancestors of the fisher migrated to North America during the Pliocene era between 2.5 and 5 million years ago. Two extinct mustelids, M. palaeosinensis and M. anderssoni, have been found in eastern Asia. The first true fisher, M. divuliana, has only been found in North America. There are strong indications that M. divuliana is related to the Asian finds, which suggests a migration. M. pennanti has been found as early as the Late Pleistocene era, about 125,000 years ago. There are no major differences between the Pleistocene fisher and the modern fisher. Fossil evidence indicates that the fisher's range extended farther south than it does today.
