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A hobbit-sized prehistoric man who lived on the Indonesian island of Flores until about 50,000 years ago is surprising scientists in more ways than one.
Homo floresiensis, the scientific name for the extinct species, was first discovered nearly 21 years ago, challenging the idea that human evolution occurred in a clear line from primitive to complex.
Experts don’t know why Homo floresiensis—nicknamed the “hobbit” after JRR Tolkien’s fictional characters—developed such a small body yet lived in such a relatively short time period, how it crossed the deep ocean to reach the island of Flores, where to place this strange little bird on the human family tree, or why it disappeared.
An analysis of recently described Homo floresiensis fossils published Tuesday in the journal Nature Communications attempts to answer some of these questions about the diminutive human. The remains examined in the new study include a fragment of a humerus — the lower half of the upper arm bone — and two teeth discovered at a site known as Mata Menge, one of two places on the island of Flores where fossils of the species have been found.
The study authors said their findings support an existing theory that hobbits developed their small size long ago and were most likely a miniaturized version of Homo erectus, the first ancient human to leave Africa about 1.9 million years ago, with a body size and upright gait similar to those of modern humans. The remains of Homo erectus have been found on the Indonesian island of Java and elsewhere in Asia and Africa.
The researchers believe that Homo erectus became isolated on the island about 1 million years ago and underwent a dramatic reduction in body size over a period of about 300,000 years. Such a reduction in size also occurs in other animals on remote islands in response to limited resources, the study says.
“Perhaps there was no need for a large body size, which requires more food and takes longer to grow and reproduce,” lead researcher Yousuke Kaifu, a professor at the University of Tokyo, said via email. “The isolated island of Flores had no mammalian predators and other hominin species, so a small body size was fine.”
Based on the estimated length of the bone, the team calculated that the owner was 100 centimeters (about 3.3 feet) tall. Teeth found at the same site, while smaller in size, showed a “high degree of similarity” to Homo erectus teeth unearthed in Java.
Digital microscopy of the bone structure indicated it was from an adult, not a child. The complete humerus would have been 21.1 centimeters to 22 centimeters (8.3 inches to 8.7 inches) long, the smallest human limb bone fossil ever found.
Previous research has shown that the sediment layer in which the fossils are located is approximately 700,000 years old.
New Homo floresiensis revelations
This early hobbit was 6 centimetres (2.4 inches) smaller than the original Homo floresiensis specimen, a nearly complete skeleton found in 2003 in Liang Bua Cave—about 75 kilometres (46.6 miles) west of Mata Menge—and dated to around 60,000 years ago. Liang Bua Cave is the only other site where hobbit fossils have been found.
The size difference between the two could reflect natural variation, as seen within modern human populations, the authors noted. Overall, the research suggested that the hobbit species’ small size remained remarkably consistent over long periods of time.
The newly analyzed finds, along with other teeth, a jawbone, and a skull fragment excavated at the same site and previously described, represent four hobbit individuals. Together with the more recent Liang Bua fossils, they suggest that the diminutive people were able to thrive on the island despite the presence of predators such as 3-meter-long (9.4 ft) Komodo dragons and crocodiles.
“The early dramatic decrease and subsequent stability in body size indicated that a smaller body size on this isolated island was beneficial for the survival of these archaic humans,” the study authors said in a statement.
The hobbit, along with the subsequent discovery of two other small-bodied, small-brained hominins that lived relatively recently—Homo naledi in South Africa and Homo luzonensis in the Philippines—and the much larger Denisovans, has led to a broader acceptance among paleoanthropologists that there were many different kinds of humans, including several that coexisted with our own species, Homo sapiens.
Before the discovery of Homo floresiensis, many experts in human evolution believed that essentially only one species of human had evolved over time, with regional variation.
The origin story of the ‘hobbit’
Not all scientists agreed with the study’s interpretation that the large Homo erectus was the ancestor of Homo floresiensis and that the hobbit represents a dwarf version of Homo erectus, said co-author Gerrit van den Bergh, a senior lecturer at the Centre for Archaeological Science at the University of Wollongong in Australia.
Others argue that the hobbit, with its small brain and chimpanzee-like wrist bones, may be more closely related to small hominids such as Homo habilis, known only from Africa.
Matt Tocheri, a Canadian research associate at Lakehead University in Ontario, said he was not convinced the hobbit was a scaled-down version of Homo erectus.
“I agree that their evidence indicates that small hominins were present on Flores at least 700,000 years ago. But why should that mean that their direct ancestors who first arrived on the island were larger?” said Tocheri, who is also a researcher in the Smithsonian Institution’s Human Origins Program.
“I think this question remains unanswered and will remain a subject of research for some time to come.”
Van den Bergh said the hobbit remains excavated at Mata Menge were found between 2014 and 2016. However, the humerus was broken into pieces and not immediately identified. One of the study’s authors later painstakingly reassembled it.
“The fossils occur in hard sandstone,” van den Bergh said via email. “(W)e are forced to use metal chisels and hammers to break up the sediments, and that is why some fossils are found in many pieces.”
To resolve the debate about the origins of the hobbit, hominin remains on Flores are needed that date from the period in which they arrived on the island, just over 1 million years ago, Van den Bergh and Tocheri say.
When the hobbit was first discovered, some experts in human evolution claimed that the bones belonged to a modern human with a growth disorder called microcephaly, a condition that results in an abnormally small head and body, and some cognitive impairment. That claim sparked a heated debate, but has since been largely dismissed.
According to the study, no signs of disease were found in the humerus.
“Every little fragment of Homo floresiensis or any other hominin is incredibly important,” Tocheri said. “These fossils are our window into the shared evolutionary past of our species. Without them, we have no idea what happened in the past.”
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