The Madjedbebe rockshelter can be found in Kakadu near Jabiru in the Northern Territory. In 1989, a small excavation at the site suggested human occupation at 60,000-50,000 years ago, but the numbers were disputed. The site was therefore further excavated in 2012 and 2015.

The team used the latest technology as seen on the increasingly popular TV programs that have done so much to turn archaeology into a glamour profession. Ground penetrating radar a-la the TV series Time Team was used to survey the area before digging. As digging proceeded, laser scanning (Time Scanners) was used to create accurate three-dimensional maps recording the placement of artefacts for later study.

A variety of dating techniques were used including OSL - optically-stimulated luminescence. This allows the last time quartz sediment was exposed to light to be dated, useful if you are trying to date artefacts or human remains surrounded by sand.  

The results of the team’s work was published in Nature in July, attracting worldwide headlines. They showed an earliest occupation date range of 65,000 years, plus or minus 5000 years. Further, that date was associated with artefacts including the earliest known global example of a ground-edge axe indicating a sophisticated and well-established lifestyle.

Within weeks, on August 9, 2017, results were published in Nature from Lida Ajer, a Sumatran Pleistocene cave with a rainforest fauna associated with fossil human teeth. These indicated an early modern human presence of 73,000 to 63,000 years ago, the same date range as Madjedbebe.

What do these and other discoveries mean? I think that we can summarise the results this way, recognising that new evidence is emerging all the time.

The date for the emergence of modern homo sapiens is being pushed back all the time, with modern homo sapiens widespread across Africa before a 100,000 out-of-Africa migration date. That date is looking increasingly uncertain to my mind.

The number of identified hominid species continues to increase, with modern humans living alongside them in the same time space, and indeed the same geographical space in some cases, for extended periods.

The DNA evidence shows interbreeding between hominid species, casting doubt on the old idea of straight-line evolution in which modern humans simply supplanted other hominid species such as the Neanderthals. Rather, there may have been parallel and overlapping evolutionary paths. We carry our complex past in our DNA!

As the time span of Aboriginal history increases, so does the range of environmental changes they were subjected to. We cannot understand Aboriginal history unless we understand those changes.

There is therefore a growing need for a full and understandable environmental history of this continent, accessible to all.

Jim Belshaw’s email is ndarala@optusnet.com.au. He blogs at newenglandaustralia.blogspot.com.au and newenglandhistory.blogspot.com.au