The Hobbit, or to the Origins of Human Evolution and Back Again

In a cave in Indonesia there lived a hobbit. In fact, an entire community of hobbits. They appear to have lived there for hundreds of thousands of years - but we only recently discovered  their existence and still know very little about them.

These are not the merry, food-and-song-loving characters from Tolkien's novels but an ancient hominin species, scientifically known as Homo floresiensis. Named after the island of Flores, where its fossils were discovered, this species earned the nickname “hobbits” for their diminutive stature—just a bit over one meter tall. Twenty years after their initial discovery, these “hobbits” remain an enigma. When and how did they arrive on the island? Who were their ancestors? And how do they fit into the evolutionary tree—or more precisely, the tangled shrub of the evolution of our hominin family? What factors caused their small size, and why? Various theories, sometimes conflicting, have been proposed over the years. A recent study, which focused on an arm bone and a few teeth found on Flores, offers new insights - though it is unlikely to settle the ongoing debates. 

hese are not the merry, food-and-song-loving characters from Tolkin’s novels, but an ancient hominin species. Painting of Homo floresiensis, skull and face | Mauricio Anton / Science Photo Library

"It's A Different Species”

Our story begins in 2003, when researchers from Indonesia and Australia were searching for fossils in the Liang Bua cave in the mountains of Flores Island.They hadn’t anticipated discovering a new hominin species; they were searching for Homo sapiens fossils, hoping to uncover evidence of a stopover on the migration route taken by our ancient ancestors on their way from Asia to Australia. The dig unearthed many animal bones, including those of the Stegodon, a genus of dwarf elephant that lived on the island and has since become extinct. Nothing stood out as unusual or exciting, until they stumbled upon a skull in September. “A member of our team who specializes in animal and human bones came down and said, “Yes, I’m sure that’s a human bone. But it’s very small,” Wahyu Saptomo, one of the field archeologists working at the site, told the scientific journal Nature.

His colleague, Richard ‘Bert’ Roberts, also said that it was immediately clear that it was a very small skeleton. We first thought, “Oh, it’s a child.” …  But Rokus said, “No, no, no, it’s not a child. It’s not modern human at all. It’s a different species.”

The researchers, who were not experts in hominin skeletal remains, invited Peter Brown, a paleontologist from Australia, to come and look at the remains. They faxed him a sketch of the findings, but he said it didn’t convey much. He agreed to come to Indonesia, though he was skeptical that the team had indeed found a fossil of a new species. “I was interested and willing to go to Jakarta. It’s an interesting place to visit. I like the food. I like the atmosphere and the culture and every­thing else” said Brown, “but I didn’t expect to find anything interesting or important. At the most, I thought it was going to be a sub-adult modern human skeleton, probably dating to the Neolithic period or maybe a little bit earlier. The other possibility was a pathological individual, someone with a growth disorder.”

But when Roberts arrived at the site and saw the fossilized jawbone, everything changed. “And it was in about six seconds, maybe less, of looking at the lower jaw, I knew it couldn’t have been a modern human lower jaw,” he said.

“It was in about six seconds, I knew it couldn’t have been a modern human lower jaw”. The jaw found on Flores island in 2003  | Javier Trueba / MSF / Science Photo Library

Small Skull, Primitive Tools

A year later the researchers described their findings in two articles published in Nature. They had an almost complete skeleton of an adult female, along with numerous stone tools, similar to some of the earlier tools found in Africa. This individual stood just a few centimeters over one meter tall, with a skull volume of only 400 milliliters - about one-third the size of a modern human female's. Brown, who measured the skull, said that he was astonished when he saw the results. “The last time things with a brain that size walked was around about 2.5 million to 3 million years ago. It was not making any sense at all.”

Initial dating suggested the fossils were around 18,000 years old, but further analysis a few years later indicated they might be closer to 60,000 years old. Some anatomical features resembled those of Homo erectus, a hominin species that lived in Africa and Asia until about 110,000 years ago, though these remains were significantly smaller. Other features resembled even earlier species, like Homo habilis or even Australopithecus, which aren’t classified as part of the Homo genus. However, as far as we know, these species never left Africa.

Paleontologist Bill Jungers remarked that when he read about the discovery “I had to check the date to make sure it wasn’t April Fool’s Day. It was so preposterous…”

Nonetheless, some researchers believed that the skeleton belonged to a member of our species, Homo sapiens, suggesting that her small size and unusual anatomical features resulted from some genetic mutation. They suggested it was possible that she had microcephaly - a condition characterized by an abnormally small head circumference. Others proposed that she might have had Down syndrome. However, additional findings from the cave revealed that several small hominids had lived there and the disease hypothesis was eventually abandoned. Today, remains from at least 14 individuals have been found in the cave, though none are as complete as the first skeleton, and some remains consist of only a few teeth.

"I think the view now is: yup, it’s not a diseased modern human,” Roberts said in 2014. “But whether it’s a shrunken down version of a Homo erectus, or whether it’s something more ancient like a Homo habilis, or even an australopithecine who’s managed to struggle out of Africa — that’s still pretty much up for grabs.”

The volume of the skull that was found was 400 milliliters - about one-third of that of a modern woman. Homo floresiensis skull (left), alongside a modern human skull | Equinox Graphics / Science Photo Library

From Africa To Flores?

In 2017, a study was published in which researchers sided with the second hypothesis, that the "hobbits", Homo floresiensis, originated from an early hominid species with roots in Africa. Using novel methods to examine skulls and other bones  of Homo floresiensis and other hominin species - H. erectus, H. habilis, H. sapiens and others, the researchers concluded that the fossils from Flores are closer to Homo habilis, which lived in Africa until 1.4 million years ago, than to Homo erectus, which lived in Asia at a later time

“When we did the analysis there was really clear support for the relationship with Homo habilis. Homo floresiensis occupied a very primitive position on the human evolutionary tree,” said Mike Lee, one of the authors of the article, in an interview to the scientific journal Australian Geographic. “We can be 99 percent sure it’s not related to Homo erectus”.

Based on the evolutionary tree they constructed, the researchers argued that the lineage leading to the “hobbits” diverged from other known hominins at least 1.75 million years ago, likely in Africa. But how did the “hobbits” journey from there to an island in Southeast Asia? The researchers had no definitive answer.  “It’s possible that Homo floresiensis evolved in Africa and migrated,” said Debbie Argue, who headed the study, “or the common ancestor moved from Africa then evolved into Homo floresiensis somewhere”. However, not all scientists accepted these conclusions, and as we will see, later studies provided support for the idea that the “hobbits” originated from Homo erectus.

Related to H. habilis? H. erectus? Or perhaps another species? Australopithicus (left), Homo habilis (center) and Homo erectus |  Science Picture CO / Science Photo Library

Ancient Humans On Islands

The discovery of the fossils on the island of Flores encouraged scientists to search for hominin remains on other islands in the area. Until then, the prevailing view was that ancient humans, such as Homo erectus, only reached places they could walk to. They reached Indonesia, but only the islands that had been connected to Asia by land bridges over the last 1.5 million years, the period during which Homo erectus lived there. However, Flores was not one of these islands: reaching it would have required crossing the sea somehow. If the “hobbits” managed to reach Flores,  could there also have been ancient humans on other islands?

The island of Luzon in the Philippines was also never connected to Asia. In the past, therefore, archeologists excavating there assumed they would find, at most, fossils of our species, who, tens of thousands of years ago, already knew how to build simple boats to travel between islands. Homo sapiens arrived in Asia within the last  50,000 years, so the researchers tracing human origins did not see the need to excavate in archaeological sites dated to earlier times. This was what Filippino archeologist Armand Mijares did, when he excavated Callao Cave on the island in 2003. “Most Southeast Asian archaeologists would only excavate cave sites up to two meters, and they would stop,” he said in an interview to National Geographic.   

The “hobbits” convinced him to revisit the site in 2007 and dig further. He and his team found many animal bones, as well as one bone that appeared to be part of a human foot. They sent it to Australian paleontologist Philip Piper, who confirmed it was indeed human. “He called me up and said, ‘Hello mate, you've got human remains’.” said Mijares. “And I said, really? Then we'll go grab a beer!”

The ancient foot bone was dated to 67 thousand years prior to our time, but the researchers were unsure who it belonged to - Homo sapiens who arrived in the area earlier than previously thought? Homo erectus? Or perhaps another species?

 Hominin remains? Then we’ll go grab a beer!  Piper with the foot bone found on the island of Luzon | Lannon Harley, ANU

 

The Man from Luzon 

To answer this question, more fossils were needed, and indeed, such fossils were found - in the same cave, in 2011, with additional discoveries in 2015. The discovered remains included seven teeth, two finger bones, two toe bones and a part of a femur bone. While not extensive, even such findings can provide valuable data. In 2019, a study argued that the bones were sufficiently different from those of Homo erectus and any other known species to declare the fossils a new species - Homo luzonensis, the man from Luzon. 

“There are some really interesting features - for example, the teeth are really small," said Piper in a press release. “The size of the teeth generally, though not always, reflect the overall body-size of a mammal.” Therefore, researchers believe that the ancient humans from Luzon were of short stature. Unfortunately, without additional bones,  they can’t say much beyond this, and certainly not determine their actual height.   

Much like the “hobbits”, the people of Luzon also displayed an odd combination of characteristics, some resembling very early species and others resembling later ones. "It's quite incredible, the extremities, that is the hand and feet bones are remarkably Australopithecine-like.” said Piper. “The Australopithecines last walked the earth in Africa about 2 million years ago and are considered to be the ancestors of the Homo group, which includes modern humans. So, the question is whether some of these features evolved as adaptations to island life, or whether they are anatomical traits passed down to Homo luzonensis from their ancestors over the preceding 2 million years."

As is often the case in science, especially in a field like human evolution where there are many researchers but few findings, not everyone was quick to agree with Piper and his colleagues. Some researchers believe that the few fossils aren’t enough to definitively declare a new species, let alone speculate about its place on the evolutionary tree. American paleontologist John Hawks told National Geographic that while the fossils did exhibit unique features, making the case for a new species reasonable, it’s also possible that some traits of the bones appear more primitive than they truly are due to their small size. Overall, his take was “I really wish there were more bones.” Perhaps future excavations will make his wish come true. 

"The size of the teeth generally, though not always, reflect the overall body-size of a mammal. ” The small teeth of the man from Luzon | Callao Cave Research Project

Early Settlement

About a year before the article that introduced Homo luzonensis to the world was published, another paper came out, revealing much earlier hominin settlement in the island of Luzon. At a site dated to approximately 709,000 years prior to our time, 57 stone tools and various animal bones showing cut marks made by those tools were found, including bones of turtles, lizards, as well as deer, local rhinos, and stegodons. No human bones were found, so we can’t determine which species they belonged to, but they may very well have been the ancestors of Homo luzonensis. They might also have been relatives of Homo floresiensis, the “hobbits”, who reached the island that now belongs to the Philippines before eventually arriving on the Indonesian island: “A hominin presence in the Philippines about 700,000 years ago is indeed potentially a first step towards solving the mystery of the origin of the Flores hominins,” said Thomas Ingicco who headed the research, in an interview with New Scientist. 

There was also evidence of very early settlement on Flores. Stone tools and animal bones with cut marks on them were found at a site dated to about one million years ago. In the same area a lower jawbone and six teeth were later discovered, which were dated to around 700,000 years ago. The jaw and teeth were also small and resembled the teeth of Homo floresiensis found in the Liang Bua cave. In a recent study more fossils from the same period were uncovered: two teeth and a part of a humerus (arm bone). 

The humerus is less than 9 centimeters long, and it is smaller and narrower than that of the 60,000-year-old fossil found on the island. However, an examination revealed that it belonged to an adult. “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,” said Adam Brumm, a co-author of the paper. “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.”

“The smallest upper arm bone known from the hominin fossil record worldwide”. The recently discovered bone (left) next to the humerus of a Homo floresiensis fossil, found in 2003 | Yousuke Kaifu

Many Ways To Be A Human

The features of the 700,000-year-old fossils, especially the teeth, are quite similar to those of Homo floresiensis.  However, some of their traits resemble those of Homo erectus, particularly fossils found on the island of Java in Indonesia. Researchers suggest, therefore, that the “hobbits” evolved from Homo erectus, not from more primitive species, as previous studies claimed. They propose that the population that lived on the island 700,000 years ago represents an intermediate stage between Homo erectus and Homo floresiensis.

“The evolutionary history of the Flores hominins is still largely unknown”, said Brumm. “However, the new fossils strongly suggest that the “hobbit” story did indeed begin when a group of the early Asian hominins known as Homo erectus somehow became isolated on this remote Indonesian island, perhaps one million years ago, and underwent a dramatic body size reduction over time”. 

How did the ancestors of Homo floresiensis, the "hobbits", reach Flores, and how did the ancestors of Homo luzonensis reach Luzon? We still don’t know, but some researchers have hypotheses. “If rhinos can swim and get to places, certainly we can think of erectus, floresiensis, and luzonensis not necessarily just swimming but at least rafting, if not boating,” says paleontologist Michael Petraglia in the interview with National Geographic. “It's just pure speculation, but you could posit that and make some convincing arguments.”

This paper is unlikely to be the final word on the matter, and the debate regarding the origins of the “hobbits” will continue. One thing we do know now is that the ancestors of Homo floresiensis were already very small 700,000 years ago. That alone teaches us a lot. Yousuke Kaifu, who led the recent study, told Live Science that the rapid emergence of the “hobbits’" new, small body shape demonstrates that there are many directions in which human species can evolve. "Acquiring a large body and large brain and becoming clever is not necessarily our destiny. Depending on the natural environment, there were diverse ways of evolution not only for animals in general but also for humans."