Ancient 'hobbits' even smaller than originally thought

The discovery of 700,000-year-old bone fragments on the volcanic Indonesian island Flores suggests that the smallest known human species was even smaller than previously thought.

An analysis of fossilized remains of two teeth and an upper arm bone — called the humerus — of an extinct hominin species called Homo floresiensis has been published in the journal Nature Communications.

These pint-sized cousins of our own Homo sapiens species lived on the Indonesian archipelago until around 50,000 years ago, when they became extinct.

When the first Homo floresiensis specimen was unearthed in Flores' Liang Bua cave in 2003, archaeologists were struck by how small this species likely was — an adult would have stood at 106 centimeters (3 feet and 6 inches), which is about as tall as a modern 4-year-old. 

It inspired them to call the species ‘Flores man' or ‘Hobbit man', owing to its diminutive stature and the popularity of Peter Jackson's Lord of the Rings films at the time.  

But the species' origin and the cause of its short stature remain a mystery. Now, this new discovery has further shaken our understanding of the Flores hominins. 

World's smallest humans 

Finding ancient humans on Flores Island is hard, said archaeologist Adam Brumm from Griffith University in Australia, who was part of the team that made the discovery. 

"There's been years and years of digging. [Excavations have been] finding thousands of fossils from other types of animals, [like the] Stegodon, Komodo dragons and giant rats. But it's only this tiny little handful of human fossils that we've found," Brumm said.

About a decade ago, Brumm's research group was chiseling through layers of hardened sandstone in Mata Menge, a site 76 kilometers (47 miles) from the Liang Bua site where the first Hobbit man was found, when they first uncovered the new humerus. 

It took a moment to realize what they'd found, but surprise quickly turned to delight. 

"We weren't really sure what it was," Brumm said, "but it was quite similar to the fossils from Liang Bua cave, which is on the same island.”

Analysis confirmed the humerus to belong to an individual Homo floresiensis who lived around 700,000 years ago. 

Now, fresh comparisons with other specimens found the humerus to be the smallest ever recorded from any hominin species found.

The individual Homo floresiensis was about 1 meter in height. The authors said this indicates the species did not change in physical features much before it went extinct 50,000 years ago.

"Now we have these three extra fossils … when we move forward 650,000 years in time, the species had not changed that much … you can see that there's definitely an ancestral relationship with the earlier species," said Brumm. 

Did the hobbits of Flores shrink over time?

Flores Island's Hobbit man have been puzzling archaeologists since their first discovery. 

Some theories suggest the species was already a small-sized hominin before it landed on the island. 

Authors of the study said their research supports a different theory, namely that Hobbit men were descendants of a larger-bodied species of humans that shrank over time. 

"[We think they] migrated from the continent, getting stuck on this remote island of Flores and then [undergoing] dwarfing through time following this principle known as the ‘Island Rule'," said Brumm. 

This so-called island rule, he explained, was a process by which large-bodied mammals became isolated on islands and grew smaller over generations. 

But if this was the case, archaeologists would have predicted finding another Flores hominin of an intermediate height between Homo erectus and Homo floresiensis, said Susan Larson of Stony Brook University, who was not involved in the study. 

"The fact is this [specimen] is as small, if not smaller, than the Liang Bua [specimen], suggesting that the dwarfism happened very rapidly and was maintained for hundreds of thousands of years," said Larson. 

She added that it's hard to trace their evolution for certain, because there is a possibility the new fossils could be of an outlier individual.

"When you have one isolated specimen, it's a possibility that you've got an oddball. [However,] the fact that this humerus is very similar to the LB1 humerus makes me think this was pretty typical of the species," she said.

More bones required

Matt Tocheri, an anthropologist specializing in human origins at Lakehead University in Canada, said the study adds to the mystery surrounding the origins of the Hobbit man.

"The question is whether it is a dwarfed descendant of Homo erectus, a dwarfed descendant of some other early species of Homo (like Homo habilis), or simply the descendant of small-bodied early species of Homo. I think this question remains unanswered," Tocheri told DW via email.

The issue, he said, is that there is too little archaeological evidence these Hobbits to know their history and their origins.

"These authors argue that the 'dwarfing' must have therefore occurred earlier on Flores. Sure, that might be the case, but maybe there was no dwarfing at all, or perhaps only a slight size reduction. We simply can't say for certain yet," Tocheri added.

Filling in the gaps with more specimens would help expand the history of Hobbit man, but doing so will take time — and luck.

Edited by: Fred Schwaller

Source:

Kaifu et al (2024). Early evolution of small body size in Homo floresiensis. Nature Communications.