Fossils Shed New Light on Small ‘Hobbit-Like’ Humans That Lived on a Remote Island

Until some 60,000 years ago, petite early humans standing just over three feet tall lived on Flores Island in what is now Indonesia. These individuals—called Homo floresiensis and nicknamed the “hobbits” after J.R.R. Tolkien’s small Middle-earth inhabitants—were shorter than today’s average human 4-year-old.

Many questions about the diminutive species remain unanswered, but now, newly examined fossils—including the smallest adult human arm bone in the fossil record—are helping scientists unravel the mysterious origins of H. floresiensis. Some of the hobbits’ ancestors may have been even shorter than thought, according to a study published Tuesday in the journal Nature Communications.

The modern story of H. floresiensis starts in 2003, when scientists unearthed a nearly complete female skeleton in the Liang Bua cave on Flores Island. They dated the skeleton to around 60,000 years ago and determined the individual stood roughly 3.5 feet tall.

Then, in 2016, researchers found more hominin fossils on a different part of the island, at a site called Mata Menge. They dated the teeth and partial jawbone to around 700,000 years ago, but they couldn’t determine the height of the individual they belonged to.

Now, archaeologists have studied two more teeth and an adult’s partial upper arm bone found at Mata Menge. From these fossils, “we could finally determine the body size” of this hobbit ancestor, lead author Yousuke Kaifu, an evolutionary anthropologist at the University of Tokyo, tells New Scientist’s Michael Marshall.

They were able to deduce that the 700,000-year-old individual was even shorter than its 60,000-year-old counterpart—by about 2.4 inches, per NBC News’ Mithil Aggarwal.

That realization was a surprise. Researchers had assumed that older generations of H. floresiensis were taller than their descendants. They’re still trying to figure out why the species instead seems to have evolved to become larger over time.

Archaeologists have suggested the hobbits diverged from a larger species called Homo erectus, which might have traveled to Flores from the neighboring Java Island around one million years ago. This hypothesis makes the size difference between the different H. floresiensis generations even more perplexing: After diverging from larger ancestors, why would the hominins have gotten shorter and then, later, gotten taller?

“This is what we’re still trying to get our head round,” study co-author Adam Brumm, an archaeologist at Griffith University in Australia, tells the Australian Broadcasting Corporation’s Bianca Nogrady.

Perhaps the two fossil individuals represent natural variation in size, such as between males and females. Or maybe the conditions on the island changed over time, prompting evolution, scientists suggest. To know for certain, archaeologists will likely need to find fossils that fill in the long gap between the 700,000-year-old and 60,000-year-old specimens.

Whatever the reason for the change, the team has “convincingly shown that these were very small individuals,” says Dean Falk, an evolutionary anthropologist at Florida State University who was not involved with the study, to the Associated Press’ Adithi Ramakrishnan.

In general, certain species can become much larger or much smaller when isolated on islands. Creatures that would be little on the mainland, such as birds and lizards, tend to become massive in island settings—producing the 50-pound dodo and the ten-foot-long Komodo dragon, for example. Animals like humans and elephants, which would typically be big, might shrink on islands.

So, in some ways, the idea that H. erectus migrated to Flores Island and became smaller until it was hobbit-sized makes sense. “Perhaps there was no need to be large-bodied, which requires more food and takes longer to grow and breed,” Kaifu tells CNN’s Katie Hunt. “The isolated island of Flores had no mammalian predators and other hominin species, so small-body size was OK.”

But uncertainties remain about the hobbits’ evolution. Not everyone is convinced that H. floresiensis arose from H. erectus—in part because archaeologists have not found any H. erectus fossils on the island. Another possibility is that H. floresiensis descended from Homo habilis, an African species that was already small, then moved across Asia and eventually ended up on the island.

Another lingering question? How the ancestors of H. floresiensis—whoever they are—ended up on the remote Flores Island to begin with. Archaeologists have not discovered any evidence to suggest they made rafts or boats. One possibility is that they hitched a ride on floating vegetation, then became stranded. Once marooned, they adapted quickly to the ebbs and flows of their environment, including the availability of food.

Their arrival was “probably a freak event, we don’t know,” says study co-author Gerrit van den Bergh, a paleontologist at the University of Wollongong in Australia, to NBC News.

“On the mainland they can move, but on an island, they’re stuck,” he adds. “So, they have to adapt to changing climates.”

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.