Komodo Dragons (Varanus Komodoensis) are the largest lizards in the world, growing to a length of 3 meters (10 feet) and weighing 70 kg (150 lbs.) or more. Only a relic population of 3,000-plus dragons survives in the wild, but these giant lizards were once the top predators throughout much of Australasia. Their final refuge consists of a few small islands in the strait between the larger Indonesian islands of Flores and Sumbawa. Once the hunting preserve of the sultans of Bima, the islands of Komodo, Rinca and Gili Motang are now part of Komodo National Park. /> />These islands are part of Wallacea, a transitional ecological zone between continental Eurasia and Australia-New Guinea. With Charles Darwin, Alfred Russel Wallace was the co-discoverer of evolution by natural selection. The first scientist to recognize the significance of the remarkable plant and animal life forms on these Australasian islands, Wallace essentially invented the science of biogeography. (1) /> />During a glacial maximum — the last one was about 18,000 years ago — much of the northern hemisphere is covered by continuous ice sheets or glaciers. Sea levels drop 100 or more meters (m) below their level today, exposing the Sunda continental shelf under the South China Sea and joining the islands of Sumatra, Borneo, Java and Bali to the mainland of southeast Asia. /> />The gates of Wallacea are deep ocean straits that do not become dry land during glacial maxima. The Wallace Line tracks south from the Makassar Strait between Borneo and Sulawesi to the Lombok Strait separating Bali and Lombok, while the Lydekker Line follows the strait between Timor and northern Australia along the edge of the Sahul shelf north to the west coast of New Guinea and the Raja Ampat islands. /> />During glacial maxima, terrestrial animals ranged freely across the connected pieces of the Asian continental land-mass as well as the continuous Sahul continental shelf linking Australia and New Guinea. /> />The Wallace and Lydekker lines are filters, not absolute barriers. Plant and terrestrial animal species did enter Wallacea, including elephants and rats from Asia, as well as reptiles from Australia, most notably ancestral Komodo dragons. But other large mammals were effectively blocked from entering Wallacea from Asia until comparably recent times. This included bovids such as the banteng (Bos javanicus), a species of cattle endemic to Southeast Asia as well as predators such as canids (wolves, etc.) and big cats. The farthest east that any of the big cats ever got was Bali; the last Bali tiger (Panthera tigris balica) was killed by human hunters in 1937.