In a recent study reported in Global Ecology and Biogeography, Dr. Meiri and his colleagues looked at a theoretical optimum body size towards which mammals are expected to grow, on both island communities and on the mainland.
“Contemporary evolutionary thinking maintains that smaller island mammals will rapidly grow larger towards the optimal size, while bigger animals will rapidly shrink due to the constraints of competition on the islands. The researchers found that island isolation per se does not really affect the evolutionary rate, the rates of diversification of species, or the rate at which body size shifts in populations of island and mainland animals.
Employing their own statistical tools incorporating large data sets that compared body sizes on various islands and on mainland communities, Dr. Meiri and his colleagues found no such tendency for bizarrely-sized animals to develop on islands. “We concluded that the evolution of body sizes is as random with respect to ‘isolation’ as on the rest of the planet. This means that you can expect to find the same sort of patterns on islands and on the mainland.”
Dr. Meiri attributes our widely held misperceptions about “dragons and dwarfs” to the fact that people tend to notice the extremes more if they are found on islands.
Or to the fact that we kill them when we find them on the mainland.