The Komodo dragon is the world’s largest lizard and can grow up to 10 feet long and weigh 300 pounds. Until recently, it was thought that the dragons became so big because they had no competition from other carnivorous predators and evolved to prey on the local Timor deer. Nowadays scientists suspect that the dragons are a relict of the megafauna that once lived acrossIndonesiaandAustralia, species that are thought to have become extinct due to human predation. (According to the renowned evolutionary biologist and best-selling author Jared Diamond, the Komodo dragon may have evolved to feed on an extinct pygmy elephant that once lived on Flores.) Either way, they are remarkable creatures that must be treated with considerable respect. Komodo dragons have been known to attack humans, and to see them in Komodo National Park, a UNESCO World Heritage site, it is mandatory to be accompanied by park rangers.