New evidence pushes back the time of disappearance of the Indonesian ‘hobbits’

31 March 2016

Eight years of further excavations and study at the Indonesian cave site of Liang Bua have pushed back the time of disappearance of the ‘hobbits’ of Flores (Homo floresiensis) from as recently as 12,000 years ago to about 50,000 years ago—around the same time that modern humans (Homo sapiens) first dispersed through the wider region and reached Australia.

Dr Kira Westaway from the Department of Environmental Sciences at Macquarie University was involved in the research.

In 2003, archaeologists uncovered the remains of a human skeleton roughly six metres (20 feet) beneath the present-day surface of Liang Bua. The skull revealed an extremely small, chimpanzee-sized brain (about 400 cm3) and the limb bones showed that this fully-grown adult would have stood about 106 cm (3.5 feet) tall. In overall appearance, it was most similar to fossil human species that lived in Africa and Asia between 1 and 3 million years ago.

This new member of the human family tree, called Homo floresiensis and dubbed the ‘hobbit’, was first reported to the world in Nature on 28 October 2004. The skeleton was initially thought to be about 18,000 years old, with fragmentary remains of other individuals found in older and younger layers thought to have been deposited between 95,000 and 12,000 years ago. The surprisingly recent age for the disappearance of H. floresiensis implied that this diminutive human species had survived on Flores almost 40 millennia after modern humans first passed through this island archipelago, reaching Australia by around 50,000 years ago.

New excavations were carried out from 2007 to 2014 and new dates for the site show that all of the skeletal remains of H. floresiensis are between about 100,000 and 60,000 years old, with stone artefacts likely made by this species continuing to about 50,000 years ago.

Dr Westaway and Macquarie University’s ‘Traps’ MQ Luminescence Dating Facility assisted in dating the skeletal material.

“The cave has one of the most complex sedimentological histories ever recorded and during the original excavations there was no clear distinction between the older pedestal sediments and younger infill. Due to the articulation in the bones there was no reason to suspect that the age for the sediments did not represent the age of the bone, so it was not deemed necessary to take samples from the Homo floresiensis holotype species itself. The ages for the sediments were correct but the association of the ages with the Hf material was incorrect – once this was determined we set about the redate,” said Dr Westaway.

Modern humans were venturing through island Southeast Asia at around this time, but whether the two species ever encountered each other on Flores or elsewhere is currently unknown. Lead author of the study, Thomas Sutikna (University of Wollongong and National Research Centre for Archaeology), said, “We didn’t realise during our original excavations that the ‘hobbit’ deposits near the eastern wall of the cave were similar in age to those near the cave centre, which we had dated to about 74,000 years ago. As we extended our original excavations each year, it became increasingly clear that there was a large remnant pedestal of older deposits truncated by an erosional surface that sloped steeply toward the cave mouth.” This erosional surface was later covered by much younger sediments during the past 20,000 years.

“Unfortunately, the ages of these overlying sediments were originally thought to apply to the ‘hobbit’ remains, but our continuing excavations and analyses revealed that this was not the case,” said co-author Wahyu Saptomo, Head of Conservation and Archaeometry at the National Research Centre for Archaeology. H. floresiensis is not the only species that suddenly disappears from the Liang Bua stratigraphic sequence about 50,000 years ago. “Vultures, giant marabou storks, pygmy Stegodon (an extinct relative of elephants) and even Komodo dragons vanish from the sequence with H. floresiensis,” according to co-lead author Dr Matt Tocheri (Canada Research Chair in Human Origins at Lakehead University and Research Associate at the Smithsonian Institution’s Human Origins Program).

Other members of the research team included Jatmiko, Sri Wasisto and the late Rokus Due Awe (National Research Centre for Archaeology), the late Mike Morwood, Bo Li, Mike Morley, Tony Dosseto and Gerrit van den Bergh (University of Wollongong), Max Aubert, Rainer Grün and Adam Brumm (Griffith University), Jian-xin Zhao (University of Queensland), Michael Storey (Natural History Museum of Denmark), Brent Alloway (Victoria University of Wellington), Hanneke Meijer (University Museum of Bergen) and Bill Jungers (Stony Brook University). The research was supported by Australian Research Council grants and fellowships, the Waitt Foundation/National Geographic Society, the Smithsonian Scholarly Studies Program, the Peter Buck Fund for Human Origins Research, and additional funds from the Smithsonian’s Human Origins Program, the University of Wollongong, the Victoria University of Wellington, and the Villum Foundation.

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