The National Geographic has an article on dinosaurs from Transylvania in which they say Islands are wonderful natural laboratories for the study of
evolutionary change and for that reason have long attracted the
attention of biologists. Large animals often become smaller on islands and small ones become larger. This phenomenon is known as the "island rule."

Those sentences remind of sitting around a campfire in the Sierras with a friend – maybe 45 years ago. As I was staring at the fire, I noticed that the fire didn't actually touch the logs. It seemed to start just a little above the wood being consumed. I asked my friend, who was  somewhat of an amateur scientist, Why doesn't the fire touch the wood? 

My friend watched the fire for a few minutes as he thought over the question. Finally, he said, It's the fire principal. A relative of the Island Rule, I guess.