The history of Queensland encompasses both a long Aboriginal Australian presence as well as the more recent periods of European colonisation and as a state of Australia. Before being charted and claimed for the Kingdom of Great Britain by Lieutenant James Cook in 1770, the coast of north-eastern Australia was explored by Dutch and French navigators. Queensland separated from the Colony of New South Wales as a self-governing Crown colony in 1859. In 1901 it became one of the six founding states of Australia. Indigenous people Established theories estimate that between 50,000 to 60,000 years ago, humans first arrived in Australia - although some theories suggest this figure to be much higher. They are thought to have arrived either by boat or by land bridge. The most likely route was from Southeast Asia across the Torres Strait. During the initial ten thousand years, these people and their descendants are thought to have traveled over much of the continent. Around 25,000 years ago, an ice age began with a rapid drop in the temperature of the earth of eight degrees. Food was difficult to find and this led to the origin of seed-grinding technology. This climate change is estimated to have lasted for over 10,000 years. As the temperature rose, the land bridges from Southeast Asia and to Tasmania were reclaimed by the sea. About 15,000 years ago, global temperatures warmed and rainfall increased along the eastern coast of Australia. The inland of Queensland, also receiving rainfall, again became habitable. Coastal lands decreased due to rising sea levels and tropical rain forests spread. The Kalkadoon people of the inland central gulf region, dug wells 10m deep to maintain their supply of freshwater. From 10,000 years until European arrival, despite the favourable warmer climate, humans were unable to develop either agriculture or animal husbandry due to the lack of domesticable cereal plants or suitable animals. When James Cook explored and charted the east coast of Australia in 1770-72 he was able to navigate close to shore in shallow water as HMB Endeavour was flat bottomed, so he and the other scientists on board had plenty of time to examine the land through telescopes whilst depths were taken every few metres for the charts, but they reported they saw no evidence of either agriculture or permanent structures, which caused them to believe the people were nomads and therefore the land was "Terra Nullius"