Early human occupation at Devil's Lair, southwestern Australia 50,000 years ago

New dating confirms that people occupied the Australian continent before the earliest time inferred from conventional radiocarbon analysis. Many of the new ages were obtained by accelerator mass spectrometry C-14 dating after an acid-base-acid pretreatment with bulk combustion (ABA-BC) or after a newly developed acid-base-wet oxidation pretreatment with stepped combustion (ABOX-SC). The samples (charcoal) came from the earliest occupation levels of the Devil's Lair site in southwestern Western Australia. Initial occupation of this site was previously dated 35,000 C-14 yr B.P. Whereas the ABA-BC ages are indistinguishable from background beyond 42,000 C-14 yr B.P., the ABOX-SC ages are in stratigraphic order to similar to 55,000 C-14 yr B.P. The ABOX-SC chronology suggests that people were in the area by 48,000 cal yr B.P. Optically stimulated luminescence (OSL), electron spin resonance (ESR) ages, U-series dating of flowstones, and C-14 dating of emu eggshell carbonate are in agreement with the ABOX-SC C-14 chronology. These results, based on four independent techniques, reinforce arguments for early colonization of the Australian continent. (C) 2001 University of Washington.