Scientists Learn More About Our Hobbit Hominin Cousins
A new discovery tells us more about our human cousins, known as the Hobbits, and inspires even more questions
Hiya!
We, Homo sapiens, are the only Human species alive today, but we are by no means the only ones to have ever lived. We’re merely the last of a long line of hominin species to evolve. We even coexisted with a few of our hominin cousins before their lines disappeared, leaving us as the last surviving hominin on Earth — for better or worse.
The Neanderthals are our most well-known cousins, and we’re starting to learn more about the Denisovans. Not only did we coexist with these groups, we mated with them — as evidenced by their DNA within our modern DNA. But there are many other ancient hominin cousins we know little about. Scientists have recently gained more insights into one particular species, however, thanks to the discovery of the smallest human adult arm bone in the fossil record.
Initial Discoveries
It all started in the 1950s and ‘60s with a university-educated Dutch priest named Father Theodor Verhoeven, who lived on today’s small Indonesian island of Flores, to the East of the larger Java island.
Verhoeven worked at a Catholic Seminary on Flores but also geeked out about archeology. During his time there, he located and excavated dozens of archeological sites — and unearthed a treasure trove of Neolithic burials and grave goods along the way.
Liang Bua Cave
Archeologists continue to excavate some of Verhoeven’s sites, and one location, the Liang Bua cave, continues to reveal discoveries decades later.
In 2003, palaeoanthropologist Peter Brown, at the University of New England, Australia, and his team of scientists, including local Indonesian archeologists, excavated the Liang Bua cave and discovered a nearly complete, yet unknown, hominin skeleton.
An analysis determined the remains belonged to a female adult who lived between about 50,000 and 90,000 years ago and was over 20 years old when she died. But curiously, she was only about three-and-a-half feet (about one meter) tall.
Whoever this female was, she wasn’t a Homo sapien like us, but a previously unknown hominin cousin of ours. The researchers named them Homo floresiensis, after the island the remains were found on. Though, considering the adult H. floresiensis appears to be about the size of a modern human 4-year-old, they’ve since been nicknamed the “hobbits” after J.R.R. Tolkien’s Lord of the Rings characters.
Mata Menge
Then, in 2016, Yousuke Kaifu, a paleoanthropologist at the University of Tokyo, and his colleagues found additional hominin remains East of the Liang Bua cave, in the grasslands of the So’a Basin on Flores, at a site known as Mata Menge, which was once a riverbed.
There, Kaifu and his team unearthed six teeth, part of a skull, and a piece of jawbone — all of which seemed unusually small for a hominin. Incredibly, dating showed these remains to be about 700,000 years old — about 650,000 years older than those found at the Liang Bua cave.
The significant age difference between the remains at the two sites is staggering, yet the bones appear to belong to very small hominins. Might the remains be from the same species as those found at Liang Bue cave, just separated by several hundred thousand years?
Unfortunately, the remains were too fragmentary for the researchers to definitively tell whether the remains at Mata Menge belonged to the Liang Bua cave hominin population or were a different, earlier hominin species. And since they didn’t find any bones belonging to the body other than the head, the team couldn’t determine the body size — but that’s changed now.
Newest Discovery
Kaifu and his colleagues — Adam Brumm, a Professor of Archaeology at Griffith University in Australia, and Gerrit (Gert) van den Bergh, a paleontology researcher at the University of Wollongong also in Australia — told the story of their newest discovery in an article published by The Conversation.
The researchers explain in the article that three years before their 2016 study was published, they’d discovered fragments of a tiny limb bone in their excavations of Mata Menge. The bone pieces were in the same 700,000-year-old fossil layer as the teeth and other cranial they reported in 2016, but at the time, they assumed the bones were from a reptile, so they did not include the fragments in their paper. They say:
“We initially thought it was from a reptile, until in 2015 the curator of fossils at the Geology Museum in Bandung, Indra Sutisna, restored the bone fragment and recognised it as the shaft of a human upper arm bone. This was later confirmed by one of us (Kaifu), although initially it was thought to belong to a child because of its extremely small size.”
The bad news is that even after restoration, the humerus (upper arm bone) remains incomplete since part of it snapped off at some point. Still, even as a fragment, it’s the smallest adult arm bone in the human fossil record. But the good news is that even with the shaft snapped, the team could still determine the body size of the individual it belonged to. They published their study in August 2024 in the journal Nature Communications.
The Study
The researchers searched the bone for markings to tell them how far down the shaft the bone snapped, such as a groove that functions as an attachment point for a muscle and supports a nerve. Identifying these key bone markers helped the team determine that the shaft broke about halfway down.
With this information, the team estimated that the bone was originally about 8 or 9 inches (20.6 or 22.6 cm) long, making the Mata Menge hominin between about 3 feet, and 3 feet 9 inches tall (93 and 121 cm tall). Their best estimate is somewhere in the middle, at around 3 feet 2 inches (100 cm) tall, which is three inches shorter than the female Liang Bua hominins.
A couple of inches may not seem like that big of a size difference, but the team was surprised because they assumed the older generations of H. floresiensis, the Mata Menga hominins, would be taller than their Liang Bua descendants. But to better understand this dilemma, we must go back even further in time.
Remaining Mysteries
On the surface, it’s reasonable to assume H. floresiensis from the Liang Bua cave is an evolutionary descendent of the smaller, older hominin found at Mata Menge, considering the similarities between the remains found at both sites, their proximity, and the vast timeframe between dates. But things get murkier when we go a bit deeper.
Who Did They Evolve From?
Some experts believe the Liang Bua hominins and Mata Menga people descended from Homo habilis because they were also a small species. The problem is, fossils belonging to H. habilis have only been found in Africa (mainly Tanzania) and nowhere near Indonesia in southeast Asia.
Those who believe that H. habilis is the actual ancestor of H. floresiensis hypothesize that the Liang Bua hominins originally evolved in Africa from H. habilis, then migrated East at some point and ended up on Flores.
However, most experts, including Kaifu and his colleagues, believe the Liang Bua hominins and Mata Menge are descendants of Homo erectus, which, in my opinion, is the ultimate of all Human species.
H. erectus lived and walked the Earth from about 1.89 million to 110,000 years ago, making them the longest-living hominin species ever. For comparison, they were around about nine times longer than the 300,000-ish years our Homo sapien species has been here. The timeline means our two human species coexisted on Earth for a bit, though we don’t know if we interacted. Badassery aside, scientists name H. erectus as a likely ancestor of the Mata Menge and the Liang Bua hominins for two reasons.
One reason is that H. erectus was the first hominin species to live outside of Africa — including on Indonesia’s Java island near Flores. Another reason came when scientists found similarities in the shape characteristics of Mata Menge's and the Liang Bua hominin’s teeth and those belonging to H. erectus.
However, the idea that Mate Menge or the Liang Bua hominins descended from H. erectus has flaws.
The first issue is that while H. erectus remains have been found near Flores, on the island of Java, none have been discovered on Flores itself. The tiny arm bone is another hesitation. Kaifu and his colleagues write in The Conversation:
We should note that the Mata Menge arm bone is not necessarily Homo erectus-like. It more resembles small-bodied Homo such as Homo floresiensis and Homo naledi.
Side note: Netflix has an excellent documentary about H. naledi.
Still, the researchers explain in their article that the Liang Bua hominins have “very odd quirks of evolution,” which they say show “a mixture of archaic and modern traits” that suggest they may have evolved from H. erectus. Another possibility is that they may have developed the characteristics on their own after being isolated on an island for a long time. Ultimately, the team concludes:
In our view, the new fossils from Mata Menge confirm the hypothesis that a group of early Asian Homo erectus somehow became isolated on Flores and underwent a remarkable process of evolutionary change, giving rise to Homo floresiensis.
But perhaps the most significant issue with the idea that H. erectus is the ancestor of H. floresiensis is that H. erectus is believed to have been between about 4.5 and 6 feet (137 to 185 cm) tall — much taller than H. floresiensis.
In other words, if the Mata Menga and Liang Bua hominins are descendants of H. erectus, how and why did they become so small? The answers may have something to do with a key feature of evolution.
Why Are They So Small?
A critical feature of evolution is that it changes anything and everything about a species to help it adapt to changing environments. And it’s evolution that may explain the size difference between H. erectus and its potential Hobbit descendants.
See, species can evolve to become significantly larger (Gigantism) or smaller (Dwarfism) depending on their environment — like, say, being isolated on an island.
Animals that tend to be smaller on the mainland, like lizards and birds, are known to become significantly larger in island settings — like the 10-foot (3-meter) long Komodo dragon, which still inhabits Indonesian islands, and the 50-pound (22.6 kg) dodo. The dodo didn’t inhabit Indonesia but did live on Mauritius Island, which is just southwest of Indonesia across the Indian Ocean toward Madagascar.
On the flip side, animals typically larger on the mainland, like elephants, can shrink when isolated on islands. (Fun fact: Flores happens to be home to pygmy elephants.)
So, the idea that H. erectus somehow wound up on Flores Island, possibly by accident, and shrunk over time in isolation until it was hobbit-sized isn’t completely far-fetched. Kaifu explained to Katie Hunt of CNN:
“Perhaps there was no need to be large-bodied, which requires more food and takes longer to grow and breed. The isolated island of Flores had no mammalian predators and other hominin species, so small-body size was OK.”
Considering the size discrepancy, Kaifu estimates the descendants would have evolved smaller bodies over about 300,000 years of isolation. He suggested to Hunt,
“They were small early and then they remained small for a long, long time.”
As much as it would be nice to say Dawrfism is the ultimate answer and everything is now explained… we can’t because while it makes sense that the descendants of H. erectus shrunk over time to resemble the Mata Menge hominins, it doesn’t explain why the descendants of Mata Menge, the Liang Bua hominins, evolved to be taller. And scientists don’t yet have an answer.
How Did They End Up On Flores?
Regardless of which species our Hobbit hominin cousins evolved from, they somehow ended up stranded on the remote Flores Island — so how did it happen?
Sarah Kuta of the Smithsonian Magazine says archaeologists haven’t found evidence suggesting the hominins made or used rafts or boats. That’s not too surprising, though, considering if they did, they’d have been made from natural materials that would have decomposed long ago.
Another possibility is they were stranded or marooned somehow. Gerrit van den Bergh, who co-authored the study and Conversation article, told Mithil Aggarwal of NBC News that whoever the original Hominin species was, their arrival to Flores Island was “probably a freak event, we don’t know.”
Hopefully, more fossils will be discovered to help fill in the 650,000-ish-year gap in evolutionary history between the Mata Menge and Liang Bua populations. Ideally, archaeologists will also find fossils to determine who their ancestors were and how they ended up on the island.
What Happened to Them?
Of course, the last major question is, what happened to the Hobbits? The remains of the Mata Menge and Liang Bua H. floresiensis hominins tell us they inhabited Flores Island for several hundred thousand years, so what could have caused their disappearance?
Further excavations of the Liang Bua cave suggest H. floresiensis disappeared relatively recently, between about 50,000 to 12,000 years ago — which happens to coincide with a wave of our Homo sapien ancestors migrations from Africa. Maybe the timeline is a coincidence, and some other currently unknown event led to the disappearance of H. floresiensis. Or maybe, our H. sapiens ancestors wiped them out. We’ll just have to hope archeologists can unearth more answers.
Perspective Shift
Naturally, my mind is spinning with possible explanations for these mysteries, especially how any hominin species ended up isolated on an Indonesian island.
I grew curious about the area’s topography and learned that Indonesia is between the Pacific and Indian Oceans and on both sides of the equator. But more significantly, it exists on two continental shelves, the edges of continents that lie under the ocean. In this case, Indonesia shares terrestrial borders with East Timor, Malaysia, and Papua New Guinea.
The number and landscapes of Indonesia's islands vary. The latest estimate is 14,752 islands. Some consist of lowlands, while some larger islands, including Java, are more mountainous. Many of the mountains on these continental shelves are volcanic, and the islands have many crater lakes — Java alone has over 60 active volcanos. Unsurprisingly, Indonesia’s location makes it especially prone to earthquakes.
Given that the Indonesian landscapes change over time, and the number of reported islands has varied over the years, maybe Homo erectus did occupy the area at some point but geological events forced them to higher elevations and ultimately trapped them. I mean, who knows? But it sure is fun to think about.
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Interesting. One possibility that occurred to me regarding why the island residents were so small is that maybe they were isolated there on purpose. Perhaps “runts” or oddly shaped folks were banished to a place away from the rest? Or, because they were different, they chose to isolate themselves for safety, or for other reasons?