Bones found in Philippines may belong to previously unknown human relative

Thirteen fossil bones and teeth excavated in a cave in the Philippines represent an enigmatic previously unknown human species, probably small in stature and possessing an unexpected mix of archaic and modern traits, scientists said on Wednesday.

The discovery of remains of at least three individuals from this species, named Homo luzonensis, in Callao Cave on the northern part of the island of Luzon, marked the second time in the 21st century that a bygone member of the human family has been found on southeast Asian islands.

And it makes our understanding of human evolution in Asia "messier, more complicated and whole lot more interesting," says Matthew Tocheri of Lakehead University in Thunder Bay, Ont.

In a study released Wednesday by the journal Nature, scientists describe a cache of seven teeth and six bones from the feet, hands and thigh of at least three individuals. They were recovered from Callao Cave in 2007, 2011 and 2015. Tests on two samples show minimum ages of 50,000 years and 67,000 years.

In 2003, fossils of another island-dwelling species — Homo floresiensis, dubbed the "Hobbit" due to its diminutive size — were unearthed in a cave on the Indonesian island of Flores, some 3,000 km from the Luzon site. There is no indication the two species interacted or were closely related.

Homo luzonensis was a contemporary not only of the Hobbit but of our own species, Homo sapiens, which emerged in Africa roughly 300,000 years ago.

The scientists said they could not rule out the possibility that the arrival of our species in the region contributed to the demise of Homo luzonensis. The Hobbit also disappeared about 50,000 years ago at the same time Homo sapiens was spreading through the region.

The main exodus of our own species from Africa that all of today's non-African people are descended from took place around 60,000 years ago.

Homo luzonensis apparently used stone tools and its small teeth suggest it might have been rather small-bodied, said one of the study authors, Florent Détroit of the National Museum of Natural History in Paris. 

There's no sign that H. luzonensis encountered any other member of the Homo group, Détroit said in an email. Our species isn't known to have reached the Philippines until thousands of years after the age of the bones, he said. 

But some human relative was on Luzon more than 700,000 years ago, as indicated by the presence of stone tools and a butchered rhino dating to that time, he said. It might have been the newfound species or an ancestor of it, he said in an email.

Détroit said it's not clear how H. luzonensis is related to other species of Homo. He speculated that it might have descended from an earlier human relative, Homo erectus, that somehow crossed the sea to Luzon.

H. erectus is generally considered the first Homo species to have expanded beyond Africa, and it plays a prominent role in the conventional wisdom about evolution outside that continent.  Some scientists have suggested that the hobbits on the Indonesian island are descended from H. erectus.

Tocheri, who did not participate it the new report, agreed that both H. luzonensis and the hobbits may have descended from H. erectus. But he said the Philippines discovery gives new credence to an alternate view: Maybe some unknown creature other than H. erectus also slipped out of Africa and into Europe and Asia, and later gave rise to both island species.

'Smoke from a much, much bigger fire'

After all, he said in an interview, remains of the hobbits and H. luzonensis show a mix of primitive and more modern traits that differ from what's seen in H. erectus. They look more like what one what might find in Africa 1.5 to 2.5 million years ago, and which might have been carried out of that continent by the mystery species, he said.

The discovery of a new human relative on Luzon might be "smoke from a much, much bigger fire," he said.

Michael Petraglia of the Max Planck Institute for the Science of Human History in Jena, Germany, said the Luzon find "shows we still know very little about human evolution, particularly in Asia."

More such discoveries will probably emerge with further work in the region, which is under-studied, he said in an email.