Human evolution is usually portrayed as a neat linear progression, from hunched primate to tall, proud man. In 2003, a discovery on the Indonesian island of Flores scrambled that narrative.

In cave called Liang Bua, researchers found the nearly complete skeleton of a tiny human who lived between 50,000 and 100,000 years ago, and who stood just over a metre high. They declared it a new species, officially called Homo floresiensis but quickly nicknamed the “hobbit” hominin. But almost everything about these extinct people was a mystery. Where did they come from, and how did they get there?

On Wednesday, researchers writing in the journal Nature announced they had discovered much older, even tinier human fossils on Flores. The 700,000-year-old remains are helping scientists understand the origins of one of the most enigmatic members of our genus.

“These guys survived there for 650,000 years or so, which is quite amazing,” said Bence Viola, a professor of paleoanthropology at the University of Toronto, who was not involved in the research.

The research team found the new fossils in 2014 at a site called Mata Menge, which sits more than 70 kilometres away from the Liang Bua cave. Archeologists had already discovered tools at Mata Menge that are at least a million years old, but until now, there had been no human fossils to match.

In a layer of sediment that dates to 700,000 years ago and also contained stone tools and fossils of several animals, the researchers discovered a jaw fragment and teeth belonging to at least three individuals. Amazingly, the jaw was 20 per cent smaller than the smallest jaw from Liang Bua.

The research team was careful to say that until more specimens are discovered, they can’t say for sure if these even tinier people are the direct ancestors of Homo floresiensis. But the discovery helps resolve some of the arguments about the hobbits’ origins.

The species of human thought to be responsible for dispersing out of Africa, Homo erectus, was about as tall as us. Did Homo floresiensis undergo dwarfism on the island? Or are they descended from smaller, more ancient primates — Homo habilis, or even Australopithecus — that most researchers think did not leave Africa, nevermind make it to Asia? Some scientists even argued Homo floresiensis was a diseased modern human.

Because the new teeth and mandible bear none of the traits of the more primitive primates, the discoveries support the theory that Homo floresiensis evolved from Homo erectus, our own species’ ancestor. Their age, which predates Homo sapiens by 500,000 years, punctures the idea that the hobbits are just diseased modern humans.

“It seems to confirm what most of us suspected all along,” said David Begun, also a U of T paleoanthropologist who was not involved in the research. It “makes more sense, since Homo erectus had a big brain and was more sophisticated in terms of its adaptations to the environment . . . You had to be pretty sophisticated, cognitively, to get to Flores.”

That means Homo floresiensis likely shrank after reaching the island. Island dwarfism is in fact an established phenomenon: constrained by lack of food, large-bodied animals on small islands tend to shrink over millennia, a pattern observed in deer on the island of Jersey and mammoths on Siberia’s Wrangel Island. Smaller animals, meanwhile, tend to become larger-bodied, since there are fewer predators.

In fact, the elephant species that lived on Flores at the same time as the hobbits was also dwarfed — it was about the size of a pig — and the rats that lived on Flores were giant. But island dwarfism had never been observed in a primate, and on Flores it appears to have happened extremely rapidly, in just 300,000 years.

“We often think that humans create our own environment. We have cities, civilizations, agriculture — that we’re kind of immune and don’t evolve,” said Begun. “This shows humans react to the environment the same way that any other animal does.”

Mysteries of the hobbit remain. How did they get to Flores? When sea levels were lower, “Java and a lot of other islands in Indonesia could be reached by foot. But Flores is far enough that it was never connected to Asia. You always needed a boat to get there, or a raft,” Viola said. Did these early human species have maritime technology?

And the tool technology associated with Homo floresiensis appears to have never evolved, which is very unusual for that long a period — in fact, some technologies even disappeared.

Scientists hope that more discoveries on Flores will help resolve these questions.

“I would like to know more about the archeology, about the culture that they had,” Begun said. “It looks like they were on that island for a really long time, basically in total isolation. I would like to know what they were doing there.”

Source: The Star.com