There is significant debate over the date of arrival of Aboriginal and Torres Strait Islander people into the Australian continent. Until the 1950s it was often believed that arrival of the first Aboriginal people was within the last 10,000 years. In the 1950s, the dates were extended to the last Ice Age, based upon falling sea-levels at that period and the existence of landbridges linking the islands of the Sunda Shelf and the Sahul Continental Shelf with Australia, New Guinea and Tasmania. The discovery and use of C14 dating extended the dating to 40,000 years at Lake Mungo, and this was the date most frequently given. However, more recently, the analysis of sea levels has shown that coastlines 40,000 years ago were not as exposed as they were 60,000 to 70,000 years ago. The submergence of the earliest sites of occupation due to rising sea levels has meant that the earliest archaeological signature may in fact represent occupation much later than the initial time of arrival. The difficulty in establishing a date of arrival earlier than 50,000 years has been compounded by the widespread use of radiocarbon dating and the supposed "radiocarbon barrier" which establishes 40,000 years as a limit to which C14 dates can be easily and reliably extracted. This limitation has prompted many archaeologists, including Rhys Jones and Alan Thorne, to include thermoluminescence dating methods in their studies of early occupation sites. It is argued that 60,000 to 70,000 years best fits the evidence from the Human genome diversity project and a number of other new dating technologies. Some have proposed dates extending back 100,000 to 120,000 years, but these dates are criticised on technical grounds and are not accepted by most scientists. A recent study by Eske Willesev of the University of Copenhagen, of the genome of an Aboriginal man from the Western Australian Goldfields confirms that the Aboriginal population separated from the early human stock 70,000 years ago, in Africa or from Oman, and travelled fairly rapidly across south and south eastern Asia to arrive in Australia at least 50,000 years ago, before a second wave travelled into Europe and Asia, receiving some input from the Aboriginal people who had already made that journey.