In 2004, anthropologists on the Indonesian island of Flores discovered the remains of a diminutive hominin, Homo floresiensis. Now, a different team of researchers has discovered teeth and forearm fossils of the so-called Hobbit species, which they say belonged to the smallest known individual yet identified. These findings tease out details of how these small hominins evolved.
“This very rare specimen confirms our hypothesis that the ancestors of Homo floresiensis were extremely small in body size; however, it is now apparent from the tiny proportions of this limb bone that the early progenitors of the ‘Hobbit’ were even smaller than we had previously thought,” said Adam Brumm, an archaeologist at the Australian Research Centre for Human Evolution at Griffith University in Brisbane, in a university release.
Anthropologists found smaller, more ancient bones than before
The remains of H. floresiensis (pronounced flor-eh-see-en-sis) found in 2004 were dated to about 60,000 years old, about 10,000 years before the species’ extinction. Researchers determined that the small humans only grew to about 3 feet and 7 inches (109 centimeters) as adults. They quickly became known as the ‘Hobbits’ due to their stature.
The new research—published today in Nature Communications—details the teeth, jaw, and the fragment of a humerus (the long bone in the upper arm) which belonged to at least four H. floresiensis individuals some 700,000 years ago. Every fossil was smaller than the remains uncovered at Liang Bua, which are about 640,000 years younger.
“This 700,000-year-old adult humerus is not just shorter than that of Homo floresiensis, it is the smallest upper arm bone known from the hominin fossil record worldwide,” Brumm said. The recently discovered humerus was just 3.46 inches (8.79 centimeters) long, leading the team to conclude that it belonged to an adult individual just 3.28 feet (100cm) tall.
The research “strengthens the link between these early remains and the much later sample from Liang Bua, both in terms of morphology and a very small body size, even in adults,” said Chris Stringer, an anthropologist at London’s Natural History Museum who was not affiliated with the recent paper, in an email to Gizmodo. “Being able to track a single evolving hominin lineage over that time scale holds great promise for future research.”
‘Hobbit’ humans, insular dwarfism, and the hominin family tree
The Flores island humans persisted until about 50,000 years ago, around when modern humans appear in the fossil record in Southeast Asia.
In 2019, anthropologists discovered another diminutive fossil human species on the island of Luzon in the Philippines. The researchers determined that the species—Homo luzonensis—grew to about the same height as the Flores humans.
The hominins may have evolved to be small as a result of insular dwarfism, a process by which species with access to fewer resources shrink in proportion to what’s available to them. For example, H. floresiensis shared Flores with Stegodon, an extinct species of very small elephant.
In 2021, a different team of researchers found evidence of interbreeding between Denisovans—yet another group of extinct hominins—and modern humans in Southeast Asia, hinting that the small-statured species farther south could be some kind of offshoot of the Denisovans. Since the Mata Menge Homo floresiensis are about hundreds of thousands of years older than the earliest evidence for Denisovans, it seems more likely that these small-statured individuals did not descend from Denisovans. So how did the Flores Hobbits come to be?
What the Homo floresiensis fossils mean for human evolution
The recent team posits that the Flores hobbits descended from Homo erectus in Java. In their paper, the team notes the similarities between the more ancient species’ teeth and that of the 700,000-year-old hobbits. The team also cited stone tools found in the So’a Basin as an indication that H. erectus became isolated on Flores about 1 million years ago, and shrank in size over the next 300,000 years. But that is far from a sure thing.
“Although the authors argue that these finds add to the likelihood that floresiensis ultimately evolved from Indonesian Homo erectus precursors, there is still the puzzling presence in floresiensis of wrist bones that closely resemble those of Australopithecus afarensis and chimpanzees, rather than humans,” Stringer said. “Perhaps early erectus ancestors still had such wrist bones, or (what seems much less likely to me) floresiensis re-evolved this more primitive anatomy in the wrist.”
Stringer added that, while a dwarfing process may have occurred on Flores, it may have happened on other islands in the area like Sumbawa or Sulawesi.
More fossils may help to explain how the small-statured humans in our family tree emerged, as well as why they disappeared. For now, a 700,000-year-old arm bone seems to suggest a new record for the smallest ancient human.
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