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This is where scientists may find the next hobbits

New discoveries in the Philippines suggest that the mysterious Homo floresiensis may have been far from alone

Great archaeological detective stories start with unexpected discoveries in unusual places.

In May, an international team of scientists led by Thomas Ingicco revealed new archaeological findings from Kalinga, in the northernmost part of Luzon, Philippines. Until now, scientists have mostly assumed that the Philippines were first inhabited by modern humans, only after 100,000 years ago. But the artifacts unearthed by Ingicco and coworkers were much older, more than 700,000 years old.

Philippines and neighboring areas. Present land areas are shown in green, also shown is the 120-meter depth line marking ancient land areas during the last glaciation.

They didn’t find any hominin fossil skeletons, but the stone tools and the butchered remains of a rhinoceros show that somebody lived on this island long before modern people evolved in Africa.

Luzon was never connected to the Asian mainland, even when sea level was at its lowest during the Ice Ages. To get there, ancient hominins had to float. Who were they, and how did they get there?

The hobbit connection

Luzon isn’t the first deepwater island to produce such ancient evidence. In 2003, Indonesian and Australian archaeologists uncovered skeletal remains and ancient tools on the island of Flores. The bones were so strange, so primitive, that scientists named a new species, Homo floresiensis.

Most people know them by their nickname, the “hobbits.”

The best-known fossil specimens from Flores come from Liang Bua cave, where they are between around 100,000 and 60,000 years old. Those bones include LB1, a skeleton which had a tiny brain, a small body, elongated feet and toes, and apelike wrist bones.

Scientists called her “Flo”, and she was like nothing they had ever seen. The discovery gave rise to debates that are still raging, 15 years later. Who were the ancestors of the hobbits, and how did they reach Flores? We still don’t know for sure, and the mystery has only deepened since 2004.

A cast of the LB1 “Flo” skeleton, on exhibit at the Royal Belgian Institute of Natural Sciences. Ghedoghedo (via Wikimedia) CC-BY-SA 4.0

The hobbit bones were a big surprise. Still, as early as the mid-1990s, archaeologists knew that some ancient tools on Flores went back to the Middle Pleistocene. That was long before modern humans could have reached the island.

After the hobbit fossil discovery at Liang Bua, a team including Adam Brumm, Mark Moore, and Gerrit van den Bergh expanded excavations in the So’a Basin, covered with up to 70 meters of volcanic ash and other sediments.

The oldest site in the basin, called Wolo Sege, dates back more than a million years. At Mata Menge, van den Bergh and coworkers found a fragment of a tiny hominin jaw and six teeth. The remains come from at least three individuals who lived around 700,000 years ago.

At first, most anthropologists assumed that Homo floresiensis must have come from erectus, shrinking body and brain in the process. But hobbit bones don’t share many features with erectus, and today many anthropologists think they might have come from an even earlier, more primitive branch of our family tree.

But how widespread were they? Until archaeologists find them on other islands, we won’t know.

A tarsier, one of the mammal inhabitants of the Philippine islands. Photo: Jan Hazevoet (CC-BY 2.0)

The diversity of the Philippines

Like Flores, the Philippine Islands were once home to large mammals that are now extinct, including the elephant-like stegodonts. Other ancient species still inhabit the island. Ancestors of tiny tarsiers crossed to the islands more than 35 million years ago, while others — like macaques — reached the Philippines much more recently. This island history has given the Philippines a unique biological diversity.

Living people in the Philippines are also very diverse. Some groups have continued traditional hunting and gathering lifestyles until very recently, like the Aeta and Agta of Luzon and the Mamanwa of Mindanao. These people have very small body size and look rather different from the larger populations of the Philippines, whose ancestors farmed for thousands of years.

Anthropologists historically considered the small-bodied people as a distinct racial group, called “Negritos”. They thought that these Philippines groups were closely related to other small-bodied hunting and gathering peoples of southeast Asia and the Andaman Islands. The idea was that all Negrito populations today are remnant survivors of an ancient race that inhabited mainland and island southeast Asia before rice agriculturalists dispersed from southern China across the region.

Recent genetics shows that this historical picture is outdated. Last year, Timothy Jinam and coworkers from the National Institute of Genetics in Japan examined the DNA of these small-bodied groups. They found that the Philippines “Negritos” all share more DNA with other larger-bodied groups in the Philippines and mainland agricultural populations, than they share with mainland “Negrito” groups or Andaman Islanders. Meanwhile, Luzon groups like the Aeta and Agta have some notable genetic differences from the Mamanwa of Mindanao.

Small-bodied populations of the Philippines, the Aeta, Agta and Mamanwa, have more Denisovan ancestry than other groups outside New Guinea and Australia.

A curious genetic fact about the small-bodied populations of the Philippines is that they are more “Denisovan” than anyone else outside New Guinea or Australia. The Denisovans were a group that emerged in our evolutionary history around the same time as Neanderthals. Their DNA suggests that the Denisovans separated from the African ancestors of modern humans around 700,000 years ago, and shortly afterward from Neanderthals. But scientists know almost nothing about what the Denisovans looked like, or where they lived. So far we only know about them from the DNA of a few fragments from Denisova Cave, in southern Siberia.

Somehow, the early modern humans who eventually settled in New Guinea and Australia met and mixed with the Denisovans. The modern human ancestors of the Aeta, Agta, and Mamanwa people must have mixed with the Denisovans, too.

That high level of Denisovan mixture is not shared by other populations that anthropologists have called Negritos on the mainland or the Andaman Islands. It’s a signature unique to deepwater islands and Sahul. The island connection may mean that Denisovans themselves existed in island southeast Asia before modern humans.

It is possible, in other words, that the hobbits were far from alone.

Archaeology adds to the picture

The new discovery at Kalinga is not the first evidence for ancient tools in the Philippines. Previous archaeological surveys on Luzon have uncovered many ancient-looking stone tools.

Some of the first artifacts were found by Ralph von Koenigswald, the paleontologist famous for finding many ancient Homo erectus remains on Java. In 1957 and 1958, he visited the Cagayan Valley of Luzon. The invitation came from H. Otley Beyer, an American anthropologist at the University of the Philippines, who had collected teeth from an extinct rhinoceros from Cagayan. In two visits, von Koenigswald found simple “pebble tools,” resembling the tools from sites like Zhoukoudian, China, where the famous “Peking Man” fossils of Homo erectus had been found.

Von Koenigswald thought that these tools probably represented people who had lived alongside the extinct mammals. Even with just a few artifacts, he gave them a distinct name, the “Cabalwanian” industry. They were very different from the tools made by any people who had lived in the Philippines during the last 10,000 years.

“the geological evidence is such that one might conclude that [the Cabalwanian] is of Pleistocene antiquity” — Ralph von Koenigswald

But he didn’t find any tools together with extinct animals.

The same problem plagued later archaeologists. For example, Alfred Pawlik led a team of excavators at Arubo 1 in 2001, a site identified when a bulldozer unearthed some stone tools from a fishpond. The archaeologists found many simple core tools and flakes, and even a “proto-handaxe”, but could not place them definitively in time.

Callao Cave, in Peñablanca, Philippines, is a cave with ancient archaeological discoveries — including a 66,000-year-old foot bone. Photo: Rawen Balmana (CC-SA 2.0)

The story changed in 2003, when a team led by Armand Mijares returned to work in a large cave known as Callao Cave. During a second dig season in 2007, Mijares and his team found a hominin foot bone among many stone artifacts. They determined that this bone, a metatarsal, is at least 66,000 years old.

The Callao foot bone is very small, even compared to small-bodied peoples like the Agta. Intriguingly, it is a near-match for the size of a floresiensis foot.

The new discoveries from Thomas Ingicco and his coworkers add significantly to these earlier archaeological findings. Surveying the Cayagan Valley deposits for ancient mammals, Ingicco’s team was following the footsteps of von Koenigswald, looking for similar signs of ancient tools or bones.

The most promising site was near Kalinga, where they began to excavate in 2014. The archaeologists uncovered the remains of a rhinoceros that had been butchered with stone tools. At last, they found tools in the same ancient layer as extinct animal bones.

Geochronologists on the team focused on the rhinoceros teeth. Teeth absorb uranium from groundwater over time, and the enamel is affected by natural radiation. Studying these effects, the scientists found that the rhino teeth were approximately 709,000 years old. The layer just above the rhinoceros gave slightly a slightly younger age, and the layer below gave a slightly older age. That consistency gives some confidence that the estimates are accurate — although with an error up to 70,000 years, no one should set their clock by them.

Looking to the future

We don’t know yet if the Luzon toolmakers could have been the same population as the Flores hobbits. The tiny foot bone from Callao Cave hints that there might have been a hobbit-like population on Luzon as well.

Already it’s clear that the history of this region was complicated. Homo erectus inhabited Java by 1.4 million years ago, and someone — maybe erectus, or maybe a different population — reached Flores before 1 million years ago. On Luzon, somebody made stone tools and butchered a rhinoceros before 700,000 years ago.

And in 2016, Gerrit van den Bergh and archaeologist coworkers found stone tools at Telepu, Sulawesi, that are older than 118,000 years. That date may not seem as impressive as the much older artifacts on Luzon and Flores, but it’s still far earlier than modern humans are thought to have arrived in this region.

Who were these ancient islanders, and how did they manage these deepwater crossings so long ago?

During the last few years, the pace of discoveries in island southeast Asia has markedly accelerated, generating more and more surprises. As these discoveries continue, we may be able to answer some of the basic questions, but I expect many new mysteries will emerge.

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