"At first we thought it was a child," Michael Moorwood and his colleagues wrote, describing the tiny, fragile skeleton they found lying in an island cave a little more than a decade ago. Or if not a child, then perhaps someone stunted by disease or malnutrition.

But then more remains were dug out of the cave on the Indonesian island of Flores: skulls, teeth, joints and limbs. The largest of the skeletons would have stood no taller than 3½ feet in life — the same size as a primitive Homo species living in Africa 2 million years ago. Yet these fossils were only a few tens of thousands of years old. They appeared to come from healthy adults. And they bore an eerie almost-but-not-quite resemblance to our own bones. The facts just didn't add up.

Ultimately, archaeologists concluded that the ancient bones belonged to a member of Homo floresiensis, a diminutive cousin of our own early human ancestors given the dubious nickname "hobbits." But not everyone agreed. As Moorwood himself initially had, many thought that the "hobbit" fossils came from a sickly modern human, not a different species. To prove that they had found something entirely new, he and his colleagues would need more evidence.

Now they have it. In two new studies in the journal Nature, Moorwood — along with about two dozen colleagues based on every continent but Antarctica — describes the discovery of 700,000-year-old ancient hominin teeth, a jawbone and stone tools at a second site on Flores that appear to come from ancestors of later H. floresiensis individuals.

The remains are an order of magnitude older than anything that had been found on the island, and they hint at a strange evolutionary origin story for the tiny species: a meager founding population of larger hominins washed up on the isolated island and then rapidly evolved to become smaller and slighter to survive in a place with paltry resources.

For paleoanthropologists, "these new findings are really going to put an end to this debate about whether it's a different species," said Aida Gómez-Robles, a researcher at George Washington University's Center for the Advanced Study of Human Paleobiology. Gómez-Robles was not involved in the new research, but she wrote commentary on the findings for Nature. "It implies that Homo floresiensis lived in Flores at this small size for a very long time," she said.

And for all of us, it is a reminder that human evolution is not a linear march toward bigger bodies and brains. We exist as we are because that's what turned out to be advantageous; under different conditions, we might be entirely different creatures.

"Homo floresiensis demonstrates that very different environmental or ecological situations can make very different traits to be important," she added. 

No one knows how the ancestors of the Flores hominins arrived on the island, but it almost certainly was not by boat. Stone tools appear in the fossil record about 1 million years ago — too soon for ancient humans to be building ocean-going vessels. Instead, Gerrit van den Bergh, an archaeologist at the University of Wollongong in Australia and a lead author of both studies, thinks it's possible that a "freak event" such as a tsunami may have washed a small group of people onto the island. This is less outlandish than it sounds; after the Christmas tsunami in 2004, several survivors — including a pregnant woman — were found clinging to flotsam and trees on islands miles from their homes. And other animals have washed ashore on entirely new continents after violent storms.

"We will probably never be able to prove this," van den Bergh said.

Although the how of "hobbit" ancestry remains a mystery, we now have a who: a Homo erectus or "Java man," hominins with human-like proportions that used sophisticated stone tools and perhaps even fire.

Reconstruction of Homo floresiensis by Atelier Elisabeth Daynes.
(Kinez Riza via Nature)

To make the evidence even more compelling, the six teeth that van den Bergh's team uncovered show almost all of the same dental features as those of Homo erectus but few of the traits characteristic of more ancient species, such as Australopithecus.

"Homo floresiensis is indeed a kind of dwarfed Homo erectus," van den Bergh said.

Tools discovered with the 700,000-year-old population are much smaller than the oldest found on the island, which clock in at about 1 million years old. That suggests that the tiny beings evolved from bigger-bodied ancestors. After arriving on Flores about a million years ago, Homo floresiensis probably was subject to "island dwarfism" — a phenomenon in which large island species tend to evolve smaller bodies in response to the scarce resources and absence of predators. Ancient elephants on Flores show the same trait: dwarf stegodon skeletons found there are less than half the size of their mainland relatives.

Three hundred thousand years is a pretty fast transition in human evolution, the researchers acknowledged. But it's nowhere near the record for island dwarfism: deer that wound up on the British island of Jersey were reduced to a sixth of their old body size in just 6,000 years during the last interglacial period.

The researchers are cautious about designating their new discoveries as Homo floresiensis, noting that they have only a few teeth and a jawbone from the second site, named Mata Menge.

"The evidence we have is few and quite fragmentary," said Adam Brumm, of Australia's Griffith University, who led the effort to date the remains. He would like to find parts of the rest of the skeleton before calling the identification absolute.

But the resemblance between the two sets of bones — which are separated by about 600,000 years — is clear. They have similar molar morphology, but the later fossils show evidence of some evolved traits; their jaws are also the same. The individuals from the original Flores site were slightly larger than those from Mata Menge, but that could mean several things: perhaps a small body size increased over time, or maybe mere intraspecies variation.

In one case, the similarities are almost too striking: Van den Bergh noted that the stone tools from Mata Menge are almost exactly the same as the later ones, a rarity for the usually innovative Homo genus.

"It just seems intriguing," he said. "Why didn't their technology change? Why don't we see new elements added?"

That stability, which endured even as humans were rapidly evolving on the mainland, may have come to a swift end. In March, after reanalyzing the original Flores fossils with more advanced dating techniques, the scientists behind the original discovery announced that the last remains date to 60,000 years ago — right about the time that modern humans arrived on the island. What's more, that time frame coincides with the extinction of several other species on Flores: vultures, giant storks, komodo dragons.

“The overlap does point to the possibility that our species may well have had a hand in their disappearance,” co-author Matt Tocheri of Lakehead University, also a research associate at the Smithsonian, told The Post at the time.

That mystery, and many others about our enigmatic hobbit cousins, remains unsolved — at least for now. But their existence, van den Bergh and his colleagues are now prepared to say, is almost certainly fact. Over the course of hundreds of thousands of years, lanky Homo erectus mastered fire and Homo heidelbergensis trekked into Europe and Neanderthals refined their tools and our own ancestors appeared on the scene, each of them progressively larger in body and in brain. And all the while, Homo floresiensis was flourishing on Flores, small but scrappy, in defiance of that trend.

"Evolution is not necessarily unidirectional," van den Bergh said. "Human diversity could have been far greater than we ever realized."

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