Tag Archives: Java

Early modern humans in Sumatra before the Toba eruption

In late July 2017 news emerged that modern humans first reached Australia at least 65 thousand years ago. Confirming that the date of departure from Africa to end up in SE Asia and Australasia was  considerable earlier than previously believed, deposits in Sumatra that contain remains of early Home sapiens have yielded even older ages (Westaway, K.E. and 22 others 2017. An early modern human presence in Sumatra 73,000–63,000 years ago. Nature v. 548 online; doi:10.1038/nature23452). This resulted from a re-examination of material from the Padang Caves first excavated more than a century ago by Eugène Dubois, famous for his discovery in Java of the first H. erectus remains. A richly fossiliferous breccia in the Lida Ajer cave yielded a fauna characteristic of a rainforest biome and included two teeth that Dubois considered to be human. Several later palaeontologists confirmed his identification as have hominin specialists in the present Australian-Indonesian-American-British-Dutch-German team. The fossil assemblage has long suggested great antiquity for the site, but only now has it been dated precisely. The dating employed three methods: optically stimulated luminescence dating of quartz grains from the breccia (85±25 to 62±5  ka); uranium-series dating of speleothem including fragments of hollow ‘soda-straw’ stalactites(84±1 to 71±7 ka); uranium-series dating of gibbon and orangutan teeth found together with the human teeth (86±13 to 76±7 ka). Statistical analysis of the age data suggests 73 to 63 ka for the fauna, with a maximum age for deposition of the breccia of 84±1 ka.

Satellite image of Lake Toba, the site of a VE...

Satellite image of Lake Toba in NW Sumatra (at centre), the site of the largest volcanic eruption during the history of human evolution ~71,600 years ago (credit: Wikipedia)

Stone tools which may have been carried by anatomically modern humans into the area have previously been used to suggest a minimum date of the arrival of migrants, though they may have been carried by ­H. erectus. Remarkably, such tools have been found beneath a thick bed of volcanic ash found throughout southern Asia and in Indian Ocean sediment cores. This has been dated at 71.6 ka and represents the explosive collapse of the caldera now containing Lake Toba in NW Sumatra that was the largest volcanic event in the entire history of the genus Homo. The new age data from Lida Ajer suggests that modern humans were present in its vicinty before the eruption, a view also supported by ‘molecular-clock’ dating of the range of mitochondrial DNA carried by living SE Asian people (79 to 75 ka). So, despite the stupendous magnitude of the Toba eruption is seems likely that some of the migrants survived.  Together with the dating of the earliest Australians the Sumatran evidence is at odds with the view, widely held by palaeoanthropologists, that the ‘Out of Africa’ exodus began by crossing the Straits of Bab el Mandab between 74 and 58 ka when global sea-level fell markedly during marine oxygen-isotope Stage 4 (MIS4). A problem with that hypothesis has been that climatic and ecological conditions in southern Asia during MIS4 were unfavourable. But is seems that modern humans were already there and capable of adapting to both the climate shift and to the devastation undoubtedly caused by Toba.