The effect of insularity on mammal evolution is approached by considering endemic fossil mammals of islands in the Mediterranean. It is shown that in general the same mammals will arrive on the islands by sweepstake dispersal. Among the large mammals this includes elephants, hippopotamids and deer: all mammals known for their good swimming ability. The evolutionary changes these mammals underwent follow parallel patterns on different islands and can be explained as an adaptational process to an island environment lacking large carnivores.