The Outback is a vast desert in the interior of Australia, extending from the north to south coast of the island, and divided between tropical and monsoonal climates in the north, arid areas in the center, and semi-arid and temperate climates in the south. Aboriginal Australians inhabited the Outback for tens of thousands of years, and early European exploration of the Outback was sporadic. Afghan and Indian camel drivers played an instrumental role in opening up the Outback from 1858 on, and a telegraph line was established in the 1870s. Agriculture, tourism, and iron, aluminum, manganese, and uranium mining make up the largest industries in the Outback, and the Outback had a population of 690,000 in 2006, down from 700,000 in 1996.