New Species of Tiny Humans Were Smart, Brain Study Reveals

TALLAHASSEE, Florida, March 4, 2005 (ENS) - The first technical study of the brain of Homo floresiensis, a newly discovered species of small early humans, shows anatomical features consistent with higher thought processes, such as taking initiative, planning and language.

Homo floresiensis is a new species of human whose 18,000 year old skeletal remains were excavated from Liang Bua, a limestone cave on the remote Indonesian island of Flores east of Bali.

The skeleton is of a one meter (39 inch) tall female aged about 30. The discovery by an Australian-Indonesian team led by Professor Mike Morwood of Australia's University of New England was announced last October.

Now, Dean Falk, professor of anthropology at Florida State University, has led a team that created the first virtual computer model, or endocast, of the tiny humanís braincase. The reconstruction used three dimensional technology to reproduce details of the external surface of the brain, smaller than the brain of a modern chimpanzee.

"I thought the Homo floresiensis brain would look like a chimp's," said Falk. "I was wrong."

brain

Right frontal view with red brain cast of Homo floresiensis encased in transparent image of the skull. (Photo courtesy Washington University in St. Louis)
Among other discoveries, Falk's team found that the Homo floresiensis brainís frontal lobe, an area thought in humans to be involved in higher thinking processes, contains significant swelling. The study is reported in Thursday's issue of the journal "Science."

The researchers estimate that the tiny people lived on Flores from about 95,000 years ago until at least 13,000 years ago, during the 25,000 years that Homo sapiens was presumed, until recently, to be Earth's sole human inhabitant.

The ancient female was nicknamed the Hobbit because her small size evoked the tiny characters known as Hobbits in J.R.R. Tolkien's books "The Hobbit" and "The Lord of the Rings" trilogy.

Given the Hobbit's small brain, Falk, a paleoneurologist, was intrigued by the sophisticated tools and evidence of fire that archaeologists uncovered near the remains.

The cave where scientists found the Hobbit also contains remnants of stone tools, fire, and a pygmy elephant. Scientists say these remains suggest, but do not prove, that Homo floresiensis may have had advanced cognitive abilities for its small brain size.

Critics said she could have been an individual with a disorder that limits brain growth known as microcephaly.

Nothing is left of the Hobbit's brain in her fossilized skull, but the living brain makes lasting impressions on the interior of the skull that can be used to determine some aspects of brain structure.

With funding from the National Geographic Society, Falk and a team at Washington University Mallinckrodt Institute of Radiology in St. Louis used a computer process to reproduce the hobbit's external brain features.

They created a three-dimensional model, or endocast, based on computer tomography (CT) data gathered in Indonesia. Falk also created a physical model out of latex.

Falk

Dr. Dean Falk focuses her research on the evolution of the brain and cognition in higher primates, including hominins. (Photo courtesy FSU)
Together the two techniques provided a detailed map of imprints left on the Hobbit's braincase that corresponded to the once-living organ's shape, grooves, vessels and sinuses.

For comparison, scientists scanned brain cases in several skulls on loan from the Cleveland Museum of Natural History and the American Museum of Natural History. As they did with the Hobbit data, scientists then used the scanning results to produce virtual endocasts, three dimensional computerized representations of likely features of the brains contained in the skulls.

Falk and her team produced additional data for comparisons by measuring latex endocasts - real models cast in latex of the likely brain structures found in10 human skulls, 18 chimpanzee skulls and five skulls of Homo erectus, a hominin that lived in Asia and Africa from about two million to 25,000 years ago.

Included among the human skulls were a microcephalic skull and a pygmy skull. In microcephalic patients, chromosomal abnormalities impede normal growth of the top of the skull and the brain.

Scientists found few structural similarities between the brains of modern microcephalics and the Hobbit.

"We still can't rule out secondary microcephaly, which can be caused by exposure to infections or toxins in the womb," explains an author of the study, Charles Hildebolt, Ph.D., associate professor of radiology at Washington University.

"But there are reports that scientists in Indonesia have found more fossils like the Hobbit," Hildebolt said. "As those surface, it becomes much harder to attribute their brain size to secondary microcephaly."

Falk said the endocasts revealed "a surprising and significant swelling of the frontal lobe, along with other anatomical features consistent with higher cognitive processes."

brain

Frontal view of transparent skull that shows the encased brain cast (Photo courtesy WUSTL)
In addition to studying brain shapes, researchers conducted detailed comparisons of dimensions in the virtual endocasts. These analyses identified several similarities between the Hobbit's brain and that of Homo erectus. However, there were also significant differences between the Hobbit and Homo erectus.

Falk identified a fissure near the back of the Hobbit's brain as its lunate sulcus. The structure is similarly located toward the back of modern human brains.

"The lunate sulcus separates the primary visual cortex from the rest of the brain," Hildebolt explains. "It tends to get pushed toward the back of the brain as the occipital, parietal, and temporal lobes expand, so normally it's a sign of advanced brain development."

Falk contends that her team's exhaustive analysis refutes skeptics' suppositions that Homo floresiensis was either a pygmy or a microcephalic. "The scaling of brain to body isn't at all what we'd expect to find in pygmies, and the shape is all wrong to be a microcephalic. This is something new."

Morwood said the discovery was one of the most important early hominin discoveries of the last 100 years.

"It is a new species of human who actually lived alongside us, yet were half our size. They were the height of a three year old child, weighed around 25 kilograms and had a brain smaller than most chimpanzees. Even so, they used fire, made sophisticated stone tools, and hunted Stegodon - a primitive type of elephant - and giant rats. We also believe that their ancestors may have reached the island using bamboo rafts. The clear implication is that, despite tiny brains, these little humans were intelligent and almost certainly had language."

The scientists base their theory on charred bones and stone tools found on the island. The blades, perforators, points, and other cutting and chopping utensils were apparently used to hunt big game.

Of the find, Thomas Sutikna, from the Indonesian Centre for Archaeology, who directed the archaeological excavations at Liang Bua, said, "Every aspect of Homo floresiensis seems to yield more surprises, but the new findings about Homo Floresiensisí brain explain how she and her kin could hunt little elephants (Stegodon), make sophisticated stone artifacts and use fire. What else they were up to during their 800,000 years of isolation on the island of Flores will be incredibly interesting."

Samples of hair found during excavation of the remains of Homo floresiensis, could contain DNA that would help to clarify the relationship between this species and our own, Morwood told an international archeology conference in December.

Morwood

Professor Mike Morwood led the expedition that discovered the Hobbit. (Photo courtesy UNE)
The possibility that the skeleton was that of a dwarf has been ruled out, and analysis shows that the Hobbit was perfectly proportioned for someone her size. The discovery of the remains of similar hobbit sized individuals in other parts of Liang Bua, shows that she was a member of a population of little hominins.

"Hundreds of thousands of years of isolation on a relatively small and resource poor island with few predators selected for smaller body size," said Dr. Gert van den Bergh, project palaeontologist from the Royal Netherlands Institute for Sea Research.

As a result, Flores ended up with the smallest species of human known anywhere. The same evolutionary pressures operated on Stegodon, the only other large mammal to make it to the island unassisted. The smallest known Stegodon species, about the size of a water buffalo, also evolved on Flores.

The "little people" may have existed on the island right up to the 16th century when Dutch traders arrived, the research team learned from local stories still told on Flores today.

Professor Richard "Bert" Roberts, with Dr. Chris Turney and Kira Westaway at the University of Wollongong, have used radiocarbon and luminescence dating techniques to establish that the most recent fossil remains in the cave are 13,000 years old, still, the team has not ruled the possibility that the hobbit sized humans could have survived until relatively recently.

"There are lots of local folk tales in Flores about these people, which are consistent and incredibly detailed," Roberts said. "The stories suggest there may be more than a grain of truth to the idea that they were still living on Flores up until the Dutch arrived in the 1500s."