Researchers in Philippines have announced that they have discovered a species of ancient human previously unknown to science. It has been named as Homo luzonensis. The discovery, reported in Nature on April 10, 2019, is likely to reignite debates over when ancient human relatives first left Africa. And the age of the remains possibly as young as 50,000 years old suggests that several different human species once co-existed across Southeast Asia.
The discovery adds to a growing body of evidence that human evolution is not as linear as was once thought. It also raises some questions which are unanswered such as how the species arrived on the Luzon island and who its ancestors were.
The researchers found teeth and bone of the distinct species while digging Callao Cave, Luzon. Callao Cave is one of the limestone caves located in the municipality of Penablanca, Cagayan province, in the Philippines.
The 2019 discovery shows at least three individual bones were found in the stratigraphic layer of Callao Cave. The newly discovered species, Homo luzonensis, differs from previously identified species in the genus Homo. This included H. floresiensis and H. sapiens. However, some scientists think additional evidence is required to confirm the fossils as a new species, rather than a locally adapted population of other Homo populations, such as H. erectus or Denisovan.
The excavation did not find a complete skeleton. Seven teeth, two hand bones, three foot bones, and one thigh bone were found, thought to belong to two adults and one child. Nevertheless, the fossils provide intriguing clues to the appearance and lifestyle of Homo luzonensis. The tiny teeth suggest the human would have been shorter than 4ft tall, possibly even shorter than another ancient species, Homo floresiensis, sometimes called the ‘hobbit’, also found in Southeast Asia and dating to about the same period. The teeth are relatively simple shapes, but one premolar has three roots, which is common among modern humans.
Most intriguing was the presence of a curved toe bone, which closely resembled the anatomy of far more ancient species such as Australopithecus, known only in Africa and dating back to more than 2 million years ago. The research also finds that ‘Hobbit’ species did not evolve from ancestor of modern humans. The bone anatomy indicates a mixed lifestyle with an ability to walk on two legs and climb trees. One possibility is that this primitive trait reappeared once the species had become isolated on the island. It is also not known whether the new species, along with the ‘hobbit’, represent earlier dispersals from Africa than Homo erectus, or whether they are descendants who later shrank and evolved new anatomical traits. Another mystery is how they arrived at Luzon, a large island that has never been connected to the mainland by a land bridge. It is possible that the early humans set out to sea intentionally on some form of raft. Or it could be that people were swept there in relatively large numbers due to a natural event such as a tsunami.
The DNA test shows that the bone found in the cave was half Neanderthal. Homo luzonensis had some physical similarities to recent humans but in some other features they resemble to the Australopithecines, upright walking ape like creatures that lived in Africa between two million and four million years ago.
Earlier studies confirm that Homo luzonensis was a proficient toolmaker and hunter. In 2018, stone tools and butchered rhinoceros skeleton that are more than 700,000 years old were found near Callao Cave.
According to the researchers Homo luzonensis lived on the island of Luzon at least 50,000–67,000 years ago. The discovery could mean primitive human relatives left Africa and made it all the way to Southeast Asia, something not previously thought possible.