From the moment that the announcement of a 1-meter-tall ancient human nicknamed “the hobbit” shocked the world in 2004, supporters and skeptics alike have longed for more fossils. After the first couple years of discoveries, the research team kept digging, hoping to shore up the creature’s status as a separate species and settle the mystery of its origins. They dug at the original find site, they dug elsewhere on the Indonesian island of Flores, and they dug on nearby Sulawesi. They unearthed thousands of stone tools and tens of thousands of animal bones. But they found no human fossils. Until now.

This week in Nature, the team announces that they have found specimens of a tiny hominin at a site on Flores called Mata Menge, 74 kilometers from the hobbit’s home in Liang Bua cave. The haul is meager—a fragment of jaw and isolated teeth—but the fossils’ diminutive size suggests they belong to the hobbit’s species, Homo floresiensis, or a precursor to it. They are securely dated to 700,000 years ago, hundreds of thousands of years earlier than the hobbit—and they are about 20% smaller. Their size is “amazing!” says Christoph Zollikofer of the University of Zurich in Switzerland, who studies fossils of the human ancestor H. erectus from Dmanisi, Georgia.

To many, the finds suggest that a lineage of tiny humans evolved on Flores, emerging surprisingly soon after their ancestor, likely H. erectus, arrived about 1 million years ago. “We expected to find a large-bodied, close relative of Homo erectus,” says paleontologist Gerrit van den Bergh of the University of Wollongong in Australia, co-leader of the discovery team. “Instead we found fossils of tiny humans, even slightly smaller than 
H. floresiensis!”

The scanty new fossils are the fruit of a herculean effort at Mata Menge, in the Soa Basin on Flores. About 50 years ago, a prescient Dutch Catholic priest and amateur archaeo
logist discovered stone tools there and concluded that H. erectus had washed up on Flores, perhaps from nearby Java. No one believed him at the time, but researchers, including members of the current team, have scoured the basin ever since. Grassy vegetation and a humid climate obscure and destroy any fossils that peek from the surface, so the team had to dig through swaths of the landscape wholesale. They bulldozed off top layers of soil, employing up to 120 students and local workers to sieve tons of dirt and chisel out fossils over 10 field seasons.

Finally, in the last few weeks of the project’s final season in 2014, their labors paid off. A sharp-eyed worker spotted a hominin tooth, which was followed by a bit of lower jaw and cranium plus five more teeth, includ
ing two baby teeth.

The jaw—clearly that of an adult, as a wisdom tooth had erupted—is about 20% smaller than the two recovered from Liang Bua, which are about the size of a 5-year-old modern human child’s. The relatively thin body of the jaw and a crest on one molar link the fossils to H. erectus and H. floresiensis, but not to the earlier human ancestor Australopithecus, the team reports. That argues against one scenario for hobbit origins—that a very small, primitive hominin such as Australopithecus somehow got out of Africa and to Flores.

Because the fossils are fragmentary, “we want to have other skeletal elements before we finally conclude about taxon,” says team member Yousuke Kaifu of the National Museum of Nature and Science in Ibaraki, Japan. For now, he and his colleagues simply call it “Homo floresiensis–like.”

To arrive at the 700,000-year figure for the bones’ age, the team used radiometric techniques to date volcanic layers above and below the soil layer where they were found, and also directly dated a partial hominin tooth. From abundant animal and plant remains they built a picture of the ancient environment: savannalike grasslands watered by meandering streams and populated by pygmy elephants, giant rats, freshwater crocodiles, and carnivorous Komodo dragons.

They also examined 149 simple stone tools uncovered near the hominins, which are mostly similar to thousands uncovered elsewhere on Flores, says team member Mark Moore of the University of New England in Armidale, Australia. He notes that one kind of relatively complex tool characteristic of H. erectus appears in the Flores record only about 1 million years ago, and vanishes after that. But the other, simple tools, perhaps made by hobbitlike people, remain unchanged for hundreds of thousands of years.

Putting all the evidence together, Van den Bergh and project co-director Adam Brumm of Griffith University, Nathan, in Brisbane, Australia, tell hobbit history this way: A little more than 1 million years ago, a small group of H. erectus was marooned on Flores, perhaps washed in by tsunamis from the islands of Java or Sulawesi. Because food was scarce and small bodies were adaptive, they quickly evolved to be smaller in size, a process called island dwarfing that is known to affect other vertebrates and also produced the island’s pygmy elephants.

Several other researchers agree with this picture and praise the team’s excavation. The finds “end the argument” that H. floresiensis is a diseased modern human rather than a separate species, as some critics have argued, says paleoanthropologist Russell Ciochon of the University of Iowa in Iowa City, who was not part of the team. (That view was already tottering after the team recently redated the original hobbit skeleton to at least 60,000 years ago, thousands of years before modern humans apparently reached the region.)

Still, the fragmentary nature of the fossils leaves parts of the story open to interpretation. “The authors have done a good job with what they have—but they don’t have a lot,” says paleoanthropologist Susan Antón of New York University in New York City. 
Zollikofer says it’s possible that the Mata Menge and Liang Bua remains reflect separate colonizations and dwarfing events, given the 600,000 years that separate them. And skeptic Robert D. Martin of the Field Museum in Chicago, Illinois, says he won’t be convinced that the hobbit’s puny brain isn’t pathological until a second skull emerges.

For the team, the road ahead is clear. Van den Bergh is succinct: “More digging.”

Source: Science Mag