A discovery that seemed to throw the modern human occupation
a lot further back than was previously thought, having serious implications for rival theories of human evolution
. A later study rejected the more sensational dates.
In 1996 Aboriginal paintings in Jinmium Cave were dated using thermoluminescence. A quartz surface over some of the engravings showed a date of between 50 000 and 75 000 years BP. This was in an underlying deposit, which held human artefacts, dated as between 116 and 176 thousand years old.
The question was whether the lower deposits had been contaminated by material of later date falling into it. Thermoluminescence analyses groups of grains and may itself be subject to contamination.
A new study in 1998 using the more precise optically stimulated luminescence (OSL) showed that the base of the deposit was no more than 22 000 years old, and some of the quartz grains on the artwork were less than 10 000 years old. These dates accord with radiocarbon dating of the site.
The oldest ages (based on luminescence dating) for any human site in Australia now stand at between 50 and 60 thousand years, at Malakunanja II and Nauwalabila I.