On the Philippines' northern island of Luzon, researchers have made an exciting find: stone tools and bones from a butchered rhinoceros that date to 709,000 years ago, hundreds of thousands of years before modern humans evolved.
As Belinda Smith at the Australia Broadcasting Company reports, the find raises questions about what species of human made it to Luzon that long ago and how they traversed the ocean. But it also contributes to an increasingly complex picture of human migration. “The original story for human evolution was very basic, that maybe there was one single migration into places like South-East Asia,” says Gilbert Price, paleontologist at the University of Queensland who was not involved in the study, Smith reports. “But it's becoming so much more complicated now.”
The remains aren’t the first evidence of ancient human activity found on the island, but they are the oldest researchers could accurately date. In the 1950s, a team of U.S. researchers discovered butchered animal bones and stone tools in the Kalinga region of Luzon. But with limited dating methods, they could only guesstimate the age, suggesting a range of 780,000 to 120,000 years old. Until this most recent find, Smith reports, the only strong evidence of hominin occupation came from a foot bone found in nearby Callao Cave on Luzon, which was dated to 67,000 years ago.
In 2013, paleontologists decided to return to Cagayan Valley, near where the previous artifacts were found. “For the first couple of weeks, we didn't see much,” Gert van den Bergh, a paleontologist at the University of Wollongong in Australia tells Smith. “But we kept going, and not long after, bingo! Nearly a whole rhinoceros skeleton.”
That wasn’t all. They also found 57 stone tools including 49 sharp-edged flakes and six cores, or the stones the flakes were chipped from, and two possible hammer stones, according to a press release. The rhino skeleton had cut marks on 13 of its bones and both of its humerus bones were cracked open, giving feasting hunters access to its marrow. There were other animal remains as well, including deer, a turtle, a monitor lizard and a stegodon, an elephant relative with a weird sideways trunk. The researchers detail the find in a new paper published in the journal Nature.
To come up with a date, the researchers analyzed both the clay layer where they found the items and the enamel of a rhino tooth. The tests suggest the remains are between 777,000 and 631,000 years old. That’s 300,000 years before researchers think modern humans, Homo sapiens, even evolved.
So if modern humans didn't cut up the rhinoceros, who did? Van den Bergh tells Smith it was likely Homo erectus, the first hominin believed to have ventured out of Africa.
As Jen Viegas at Seeker reports, the species was common in Asia by that time and had four potential routes into the Philippines. But recent studies also suggest Homo floresiensis—also known as “hobbits”—could have beat Homo erectus to the area. They were found on the nearby island of Flores in Indonesia ten years ago. It’s also possible the rhino was butchered by some as-yet-undiscovered Homo species.
As van den Bergh tells Smith, the species responsible for the butchery remains speculative since the researchers found no hominin fossil evidence, and many species created the type of tools found in the region.
There’s also the question of how the ancient humans got to the island nation in the first place. As Thomas Ingicco, lead author of the study, tells Viegas, it’s most likely that they arrived accidentally, riding on natural floating rafts of mangroves tangles that could have broken from mainland Asia during typhoons or tsunamis. Much less likely, but still possible, is the idea that they came to the islands using a primitive boat.
The latest find also raises the possibility that even older evidence of ancient human activity exists on the island. And researchers are on the case. As van den Bergh says in the press release: “Now we can go looking in older strata and see if we can find more artifacts, or even better, fossil evidence.”