As sabre tooth tigers and woolly mammoths were wandering around Europe, unique, giant prehistoric animals were living in Australia -- three metre tall kangaroos and wombat-like creatures, the size of a four-wheel drive, were just some of the curious creatures Down Under. Yet mysteriously, sometime during the last 100,000 years, they disappeared forever. The extinction of these giant animals, known as megafauna, has generated great debate. One group advocates "human blitzkrieg" -- those asserting the first Australians hunted these beasts to extinction. Others, myself included, find there is too little evidence to confidently attribute responsibility to any particular factor. Nonetheless,...