IT WAS the most spectacular fossil find of a generation. The discovery that a mysterious and apparently ingenious human species may have shared the planet with our own less than 15,000 years ago captured the imagination of palaeontologists and public alike.
No wonder the diminutive Homo floresiensis, known as Ebu, discovered on a remote Indonesian island attracted critics. Some argued it was a pygmy, others that it was a full-sized human with a malformed skull and brain. Now a detailed analysis of the skull’s anatomy has laid both ideas to rest, and confirmed that Ebu is a unique species.
“Ebu’s brain has remarkably advanced features for such a tiny skull, backing up the claim that she was an advanced thinker”
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“Unequivocally it is not what you would expect a miniaturised modern human brain to look like,” says anthropologist Bernard Wood at George Washington University in Washington DC. “Nor is it like the brain of a human with a pathological microcephaly.”
What is more, Ebu’s brain has remarkably advanced features for such a tiny skull, backing up the claim that she was an advanced thinker. “It has an extraordinary morphology that’s unlike anything I’ve seen,” says Dean Falk, an expert on brain evolution at Florida State University in Tallahassee, whose team carried out the analysis.
The refusal, until now, by some anthropologists to accept the Ebu fossil as not H. sapiens echoes the reception to the first Neanderthal specimen. After that skeleton was unearthed in a German quarry in 1856, the eminent German pathologist Rudolf Virchow dismissed it as the skeleton of a modern human with rickets.
The H. floresiensis skull and other bones of one female and fragments from up to six other individuals were discovered in caves on the island of Flores in 2003 and revealed to the world last year (91av, 30 October 2004, p 8). The remarkably petite human stood just a metre tall and had a grapefruit-sized brain.
The charred bones of animals also found in the caves hint that H. floresiensis may have made hunting tools and even cooked, suggesting impressive intelligence. “We find nothing to contradict this speculation,” Falk says. “It may be that the population was hunting, making tools and using fire.”
Falk used data collected during CT scans performed shortly after the skull was discovered to build a 3D computer model of the cranial cavity. This mirrors the overall shape of the brain and reveals surface features. She compared the model with other extinct pre-humans, along with modern humans and living apes (see Diagram). The shape of the brain of H. floresiensis most closely resembled that of H. erectus, an ancestor that disappeared around 200,000 years ago.
Falk found several advanced morphological features, including enlarged frontal and temporal lobes and an extended area at the back called the lunate sulcus. The frontal lobes of our own brains are associated with forward planning and problem solving, and temporal lobes are thought to play a role in memory.
Chris Stringer at the Natural History Museum in London is more cautious though. “I reserve judgement on what kind of intelligence and technology the animal might have had,” he says. He is also sceptical of the reasoning that Ebu’s presence on the island is itself evidence that H. floresiensis had the brain power needed to build boats for a sea crossing. He suggests they could have arrived by accident, citing remarkable tales of survival after the recent Asian tsunami. “People were found hundreds of miles out to sea after several days,” he points out.
There has been a bitter row over access to Ebu’s remains (91av, 11 December 2004, p 4), which until recently were held at the National Research Centre for Archaeology in Jakarta under the care of Teuku Jacob, an influential palaeoanthropologist sceptical about its classification. The bones were returned to the fossils’ finders on 23 February.
