Miniature Mediterranean Mammoths

Insular dwarfism is a phenomenon that has occurred many times throughout evolution. What happens is that a population of some large animal becomes trapped on an island, out of contact with its mainland kin., Because the island has a limited size, it also has a limited amount of food on it, and this is a problem for a large animal that needs plenty to eat,

If the island is particularly small, of course, the animals in question are likely to die out, if not immediately, then dwindling over a few generations until they lack the genetic diversity to sustain themselves. On the other hand, if the island is a large one (such as, say, Britain) then there may not be a problem at all, and nothing happens beyond the usual genetic drift between isolated populations.