March 31, 2016

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

Findings published in Nature reveal Hobbits may have lived along side modern humans.

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, according to new findings published today (31 March, AEDT) in Nature. 

The new dateline is around the same time that modern humans (Homo sapiens) first dispersed through the wider region and reached Australia. Researchers from the Centre for Archaeological Science (CAS) at the University of Wollongong have played a pivotal role in the latest findings. 

Lead author of the study is Thomas Sutikna (University of Wollongong and National Research Centre for Archaeology) while Professor Richard ‘Bert’ Roberts, Australian Research Council Laureate Fellow at the University of Wollongong, oversaw the various dating analyses used in the study. Other UOW researchers include the late Professor Mike Morwood, Dr Bo Li, Dr Mike Morley, Associate Professor Tony Dosseto and Dr Gerrit van den Bergh. 

In 2003, archaeologists uncovered the remains of a human skeleton roughly 6 metres 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 1 metre 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 found in deposits dated to about 18,000 years ago, with fragmentary remains of other individuals found in older and younger layers (95,000 to 12,000 years old). 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 by researchers from the National Research Centre for Archaeology (Indonesia), the University of Wollongong and the Smithsonian Institution (USA), and revealed a stratigraphic sequence far more complex than originally thought. 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. 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. 

Thomas Sutikna 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 and Visiting Fellow in CAS. 

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). 

“Lots of people may have interesting ideas about why these taxa disappear together like this, but the truth is that we don’t know precisely why—and we won’t know with any certainty until much more work is done at Liang Bua and other sites on Flores,” Dr Tocheri said. 

Professor Roberts said the team dated charcoal, sediments, flowstones, volcanic ash and even the H. floresiensis bones themselves using the most up-to-date scientific methods available. 

“In the last decade, we’ve vastly improved our understanding of when the deposits accumulated in Liang Bua, and what this means for the age of ‘hobbit’ bones and stone tools. But whether ‘hobbits’ encountered modern humans or other groups of humans—such as the ‘Denisovans’—dispersing through Southeast Asia remains an open and intriguing question.” 

Other members of the research team included Jatmiko, Rokus Due Awe and Sri Wasisto (National Research Centre for Archaeology), Kira Westaway (Macquarie University), 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.