Our family tree may have grown a new branch today, with scientists announcing they have found a new species of early human in the Philippines.

Key points: New species found on Luzon island in the Philippines dubbed Homo luzonensis shows a curious mix of features

New species found on Luzon island in the Philippines dubbed Homo luzonensis shows a curious mix of features It could be a product of the same island processes that led to evolution of the "hobbit" on the Indonesian island of Flores

It could be a product of the same island processes that led to evolution of the "hobbit" on the Indonesian island of Flores Claims rely on analysis of several teeth, along with hand, foot and leg bones, but not all scientists are convinced it's a new species

An international team of researchers report today in the journal Nature that the discovery, dubbed Homo luzonensis, lived over 50,000 years ago on the island of Luzon.

They say a handful of teeth and bones are the remains of at least three individuals — a child and two adults — of the now-extinct species.

Not everyone is convinced we know how old Homo luzonensis is, or even if it really is a new species. But most experts agree the island-rich South-East Asia is fast rivalling Africa as a hotbed of hominin evolution.

Modern humans are the only living representatives of the hominin group.

The announcement of Homo luzonensis comes 15 years after the discovery of the Indonesian hominin, Homo floresiensis or the "hobbit", which was also named after the island it was found on.

It's no coincidence that new species are often found on islands, said Philip Piper, an archaeologist at the Australian National University and co-author of the paper.

"Islands are like evolutionary places of experiment, so you get all kinds of weird and wonderful things happening on islands," Professor Piper said.

"Because there are so many islands in South-East Asia, this suggests it would be a place of diversity of hominins.

"Think about the Galapagos tortoises — each island in the Galapagos chain has got its own species of tortoise."

Building on earlier discoveries

Professor Piper said he unknowingly discovered the first bone belonging to Homo luzonensis in 2007 while working at the University of the Philippines.

In material collected from the limestone Callao Cave in northern Luzon, he found a strange-looking bone that he dated to around 67,000 years old.

He knew it was from a species of Homo, but couldn't tell which.

Three long excavation seasons later and Professor Piper and colleagues dug up 12 more bone fragments from the same site, giving a total of seven teeth, two hand bones, three foot bones and one thigh bone.

Using 3D scanning and computer modelling, the researchers then compared the bones to other hominin species.

Professor Piper said that, just like the hobbit, Homo luzonensis had a unique combination of features that justified it being classified as a new species.

For example, the toe bones were curved — like those from Australopithecus, an ancient hominin that lived in Africa up to 2 million years ago — yet the crowns of its teeth were like a modern human's.

The researchers used a technique called uranium-series dating to work out the teeth were at least 50,000 years old. In addition to the original foot bone, they had also previously dated two deer teeth found alongside the Homo luzonensis bones to over 50,000 years old.

Since modern humans were in South-East Asia before this time, it's possible they encountered Homo luzonensis, Professor Piper said.

In an accompanying commentary in Nature, Matthew Tocheri from Lakehead University in Canada wrote that "one thing can be said for certain — our picture of hominin evolution in Asia during [this time] just got even messier, more complicated and a whole lot more interesting".

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 15 seconds 15 s Toe bones of Homo luzonensis (middle) are more curved than Homo sapiens (right) and more like Australopithecus (left) (Supplied: The Callao Cave Research Project Team)

'Sensational' finding

Archaeologist Adam Brumm of Griffith University's Australian Research Centre for Human Evolution called the finding "truly sensational", and said Professor Piper and colleagues had done "a very meticulous and commendable job" describing the new fossils.

A model of the Hobbit skull. No skull of Homo luzonensis has been found yet. ( Stephen Hird: Reuters )

"But we'll have no idea what this ancient human actually looked like until we have a relatively complete skull," Dr Brumm said.

"Such is life."

He added that this part of the world had shown him that "anything's possible".

"Nothing surprises me — but that doesn't mean I'm jaded," he said.

"Reading papers like this sends shivers down my spine.

"It's like the Flores 'hobbit' all over again, if not even more enigmatic."

But without bones from a complete adult arm or leg, it was impossible to calculate Homo luzonensis's height.

Professor Piper said it was "likely to have been smaller than a modern human" given its small teeth, although how much smaller, he couldn't say.

He said it could have shrunk from a larger ancestor due to a phenomenon called island dwarfism, in which large mammals generally get smaller.

It's the process believed to have been at work in the evolution of the short-statured hobbit.

'Not convinced'

Still, some say there isn't enough evidence to support the claims, such as palaeontologist Darren Curnoe of the University of New South Wales, who also works in South-East Asia.

"I'm not convinced that there's enough fossil material to inform a description of a new species," he said.

"They haven't convincingly established it is not a Homo floresiensis, for example.

"I'd liked to have seen the authors be a little more cautious and not rush to announce a new species."

Dr Curnoe was also concerned about the dating provided by the researchers.

"I don't think we know how old these fossils are," he said, but added the fossils were clearly not modern human and the findings were "potentially very exciting".

"I'm certainly quite compelled by the study that they've found something very usual and very unique."

Unfortunately — just as with the hobbit — Professor Piper and colleagues have not yet found any DNA in the fossils to help settle the question.

Focus on South-East Asia

Whether or not the new fossil claims stack up, Dr Curnoe said tropical caves like this in South-East Asia were yielding "lots of surprises" that were challenging traditional views.

"I think we've had for a long time a bias in archaeology towards Africa," he said.

"We're starting to get a sense that there seems to be a lot more diversity in places like South-East Asia that were traditionally considered evolutionary dead ends."

Despite Dr Curnoe's reservations about the work, others like palaeoanthropologist Michael Petraglia, from the Max Planck Institute for the Science of Human History in Germany, agree with Dr Brumm that the work is impressive.

"The researchers have convinced me that this is a genuine species given the fossil descriptions and comparisons," Professor Petraglia said.

"It is probable that Homo luzonensis is closely related to Homo floresiensis.

"It would not be surprising to find additional new species in places such as island South-East Asia, as hominin populations could have easily become isolated."

He said the new species could be descended from Homo erectus which was in mainland Asia and in places like Indonesia long before 50,000 years ago.

Another suggested ancestor for the new species are the enigmatic Denisovans.

Professor Petraglia said previous research on Callao Cave found stone tools and animal bones with cut marks in the same layer as the new fossils.

"[This] shows that these hominins were making efficient cutting tools and that they were able to access meat, which they probably hunted."

Excavations at Callao Cave. ( Supplied: Callao Cave Archaeology Project )

Palaeontologist Gert van den Bergh of the University of Wollongong's Centre for Archaeological Science was also positive about the findings, describing them as "spectacular".

Despite the "limited" material, he said it was "highly likely" the fossils were from a separate to Homo floresiensis.

Last year, Dr van den Bergh and colleagues reported the discovery of 700,000-year-old tools at an open grassland site called Kalinga in the Cagayan Valley, 30 kilometres from the Callao Cave — the earliest evidence of hominin activity in the Philippines.

The tools had been used to butcher a rhinoceros, but no evidence of the tool users was found at the site.

So could Homo luzonensis be the descendants of these rhino eaters?

Only time will tell.