Hobbit history gets new preface

Say hello to hobbits’ possible ancestors. Excavations of fossils from roughly 700,000-year-old hominids on the Indonesian island of Flores have reinvigorated scientific debate over the evolutionary origins and identity of Homo floresiensis, a half-sized member of the human genus — dubbed hobbits — that lived much later on Flores.

Remains of at least three individuals found at a central Flores site, called Mata Menge, probably represent early versions of H. floresiensis, says a team led by paleontologist Gerrit van den Bergh of the University of Wollongong in Australia and Japanese biological anthropologist Yousuke Kaifu. A lower-jaw fragment and six teeth excavated in 2014 come from hominids that were about as small as hobbits. These fossils look enough like hobbit jaws and teeth to be assigned provisionally to H. floresiensis, the researchers conclude in the June 9 Nature.

Researchers are divided over what the new finds imply about hobbit evolution. “Nothing related to humans on Flores has a simple explanation,” says paleoanthropologist María Martinόn-Torres of University College London. She calls the new discoveries “puzzling and exciting.”

In a second paper in Nature, archaeologist Adam Brumm of Griffith University in Nathan, Australia, and colleagues describe chemical analyses of one hominid tooth and two animal teeth, as well as of volcanic ash and sediment layers at Mata Menge, that yielded the age estimate for the finds. Excavations also uncovered 149 stone artifacts, including 47 that lay among hominid fossils, Brumm says. Nonhuman animal bones unearthed in the new dig indicate that Mata Menge hominids lived in a river valley dominated by grasslands.

Mata Menge hominids were “a dwarfed descendant of early Homo erectus that somehow got marooned on Flores,” suggests Kaifu, of the National Museum of Nature and Science in Tokyo. The Mata Menge fossils look more like H. erectus than other ancient hominids, his team reports.

H. erectus reached the Flores vicinity deep in the Stone Age, arriving on the nearby island of Java at least 1 million years ago. An unknown hominid species inhabited the Indonesian island of Sulawesi by 194,000 years ago (SN: 2/6/16, p. 7).

Hobbit fossils, previously unearthed 74 kilometers west of Mata Menge in Flores’ Liang Bua Cave, range in age from 100,000 to 60,000 years ago (SN: 4/30/16, p. 7). Stone tools probably made by hobbits date to as early as 190,000 years ago.

Stone implements previously found at Mata Menge and another Flores site date to between around 1 million and roughly 800,000 years ago (SN: 6/3/06, p. 341). The new hominid fossil finds provide the first peek at the likely makers of the Mata Menge tools, Brumm says.

Too few fossils have been found to exclude the possibility that, even if Mata Menge and Liang Bua hominids were related, they belonged to different populations that arrived on Flores at different times, Martinόn-Torres says.

Even so, the new discoveries fit a scenario in which presumably large-bodied H. erectus settled on Flores around 1 million years ago and shrank in size over the next 300,000 years, a surprisingly short time for such dramatic brain and body changes to evolve, Kaifu says. These hominids may have evolved smaller bodies over a relatively short period in response to limited island resources, proposes archaeologist Robin Dennell of the University of Sheffield in England.

But biological anthropologist William Jungers of Stony Brook University School of Medicine in New York says it’s unlikely that H. erectus shrunk to two-thirds of its initial body size and half its original brain size over only several hundred thousand years on Flores. He predicts that ongoing excavations at Mata Menge and nearby sites will uncover 1-million-year-old fossils of small-bodied hobbit ancestors that differed in many respects from H. erectus.

Like the Mata Menge team, though, Jungers says the new discoveries challenge an argument that a partial hobbit skeleton represents a Homo sapiens with Down syndrome (SN Online: 8/5/14).

Proponents of that idea disagree. Different hominids could have reached Flores at different times, as suggested by Martinόn-Torres, says Penn State developmental geneticist Robert Eckhardt. Not enough fossil evidence exists to show an evolutionary link between Mata Menge and Liang Bua individuals, Eckhardt and biological anthropologist Maciej Henneberg of the University of Adelaide in Australia argue.