Estimates of the number of people living in Australia at the time that colonisation began in 1788, who belonged to a range of diverse groups, vary from 300,000 to a million, and upper estimates place the total population as high as 1.25 million. A cumulative population of 1.6 billion people has been estimated to have lived in Australia over 65,000 years prior to British colonisation. The regions of heaviest Aboriginal population were the same temperate coastal regions that are currently the most heavily populated, the  Murray River valley in particular. In the early 1900s it was commonly believed that the Aboriginal population of Australia was leading toward extinction. The population shrank from those present when colonisation began in New South Wales in 1788, to 50,000 in 1930. This drastic reduction in numbers has been attributed to outbreaks of smallpox and other diseases to which the Indigenous peoples had no immunity, but other sources have described the extent of frontier clashes and in some cases, deliberate killings of Aboriginal peoples.