The older OSL dates are probably due to some grains not being exposed to sufficient sunlight before burial.
Based on these results, the researchers conclude that human habitation of the Jinmium site is certainly no older than 10,000 years (ie end of the last ice-age), and probably quite a bit younger, with the oldest inhabited level being perhaps 6000 years old - about the time farming began in the Middle East.
Luminescence dating is often used to determine age-estimates of sediment in stratigraphy where artefacts have been located.
Contamination from earlier or later layers can sometimes misrepresent the correct age of the sediment, hence the age-estimates for the associated artefacts may be inaccurate.
Some sites that were originally dated using luminescence have since been re-examined and found to be older or younger than initially thought.
However these layers have now been intensively re-dated using the latest and most sophisticated techniques by a dating team from La Trobe University, the Australian National University, CSIRO, the Australian Nuclear Science and Technology Organisation (ANSTO), the Australian Museum and University College, London.
"These findings mean that all the 'hype' about modern humans being in Australia before they had apparently even left Africa has been put to rest, and we no longer need to debate the issue of human origins on the Jinmium evidence," says team leader Dr Richard Roberts of La Trobe University. But that still leaves us with the fascinating question of when humans entered Australia - and whether it has any connection with changes in the pollen and charcoal records we see taking place about 120,000 years ago.