Fossil bones and teeth found in the Philippines have revealed a species of long-lost cousins of modern people who evidently lived tens of thousands of years ago, around the time our own ancestors were spreading out of Africa.
It's yet another reminder that, although Homo sapiens is now the only surviving member of our branch of the evolutionary tree, we've had company for most of our existence.
In a study published Wednesday in 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 on the island of Luzon in the northern Philippines in 2007, 2011 and 2015.
Analysis of the bones from Luzon led the study authors to conclude that the fossils belonged to a previously unknown member of our "Homo" branch of the family tree. One of the toe bones and the overall pattern of tooth shapes and sizes differs from what's been seen before in the Homo family, the researchers said.
They dubbed the new species Homo luzonensis.
These individuals apparently used stone tools, and the small teeth suggest they might have had small bodies, said study leader Florent Detroit of the National Museum of Natural History in Paris.
There's no sign that H. luzonensis encountered any other member of the Homo group, Detroit said. Our species isn't known to have reached the Philippines until thousands of years after the bones were left in the Callao Cave, he said.
Detroit said it's not clear how H. luzonensis is related to other Homo species. 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 in 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: Perhaps some unknown creature other than H. erectus slipped out of Africa and into Europe and Asia, and later gave rise to both island species.
After all, he said, remains of the hobbits and of 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 have found in Africa 1.5 million 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.
Archaeologist 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."