When the remains of the the diminutive Homo floresiensis were first discovered in 2004, the one meter-tall “hobbits” were so unexpected that many scientists spent a decade looking for any option but accepting them as a new species of humans. But with partial skeletons of at least nine individuals, the remains from Liang Bua on the island of Flores in Indonesia do appear to represent a previously unknown, small, distinct member of the human family.
And now it appears that scientists have found another.The discovery, reported in the April 10 edition of Nature, comes from Callao Cave on the island of Luzon, in the Philippines. When the first remains were found in the cave a decade ago, they were reported as being plain old H. sapiens — though from a small example. That no longer appears to be the case. With a variety of bones from the skeletons of two adults and a child, researchers have named the source of the remains Homo luzonensis, adding another branch to a family tree that seems more varied and complicated with each passing year.
What used to be naively presented (especially in the popular press) as a simple “ladder” of species ending with modern humans triumphant, has been revealed a very complex with a lot of branches whose relationship are far from clear. Not that long ago, the Earth was home to modern humans, Neanderthals, the still largely mysterious Denisovans, and the “hobbits” on Flores all at the same time. And that’s not all. Genetic research indicates there is at least one still unknown, but genetically distinct group whose traces remain in the genes of some living humans. And that is not counting the new species covered in this report from the Philippines.
A French team under Florent Détroit from the National Museum of Natural History in Paris, believes that these specimens are distinct both from modern humans, and from H. floresiensis. But if they are right about the age of these specimens—as young as 50,000 years—that means that the not-all-that-ancient Earth was home to an even broader group of human species.
The authors of the study point to differences in the teeth of the Philippine species as reasons to differentiate the remains from both H. sapiens and H. floresiensis. But there’s a far stranger feature to the bones than just the teeth.
The French team suggests that the foot bones of the remains from Callao Cave resemble more those of primitive hominins like Australopithecus than they do those of modern humans, or even human ancestors like Homo erectus. Similarly, the researchers suggest that the finger bones of the Philippine specimens show more curvature than modern humans, which might have made them more adept at climbing trees.
The problem is that all these features are not only very primitive features, they are features of ancient hominins which have never been found outside Africa. It seems very unlikely—very, very unlikely—that the specimens from Luzon represent some relic population of early hominins who somehow managed to trek to that location all the way from Africa without leaving any trace along the way.
Whether or not H. luzonensis holds up as a species, or whether additional specimens only muddy the already confusing picture, the remains coming out of the Philippines appear for the moment to be unique and interesting. They may, as with those of the “hobbit” represent a second instance of “Insular dwarfism,” a process in which large animals restricted in range may tend toward a decreased body size. They may also represent a unique form of parallel evolution in which local conditions caused the population to develop features that mimic more primitive hominins. They may also represent what many researchers first thought about the specimens from Flores—a small family group whose features are not representative of a genuine, extended population.
But the apparently primitive features in the remains are hugely interesting. If additional finds are made, and they really do indicate a direct connection to earlier forms that bypasses the known migration of H. sapiens and H. erectus, this discovery could hugely impact our understanding of human evolution and the spread of human species around the planet.
“Island southeast Asia appears to be full of palaeontological surprises that complicate simple scenarios of human evolution," says William Jungers, a palaeoanthropologist at Stony Brook University in New York.