The skeleton of the Liang Bua hominid, Homo floresiensis, is a mixed bag of characteristics that until now have been associated with very different stages of human evolution.
One of the most striking characteristics of LB1, or Ebu, is her height. At around 1 metre tall she is far shorter even than modern Pygmies, who range from 1.3 to 1.4 metres, and roughly the same size as the relatively primitive hominid Australopithecus.
But australopithecines, such as the famous Lucy, lived in Africa between 1.4 and 4.5 million years ago, whereas the Liang Bua hominid lived from between 74,000 and 95,000 years ago, or until as recently as 13,000 years ago. These dates were established by techniques used to date both the material surrounding the remains of Ebu (Nature, vol 431, p 1055 and p 1087) and the remains of other recently discovered specimens of the new species.
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Indeed, the shape of Ebu’s skull is more like that of our ancestor Homo erectus, which lived between 1.8 million and 200,000 years ago. That suggests that she, like H. sapiens, is a direct descendent of H. erectus. “Her teeth are bigger than ours. And because her teeth are big, so is her mouth. Her face projects forward, and there is no chin at all,” says palaeoanthropologist Peter Brown, the leader of the team that discovered the new species. She also has protruding brow ridges, which are typical of H. erectus.
Her hands, too, are more human-like than those of australopithecines. Since the initial discovery, the team has excavated bones from at least four more specimens of the new species, including a hand and wrist. “They are remarkably tiny – they would make a great watchmaker or brain surgeon. But there is no evidence that they lived in trees. The [hands] are more human-like, more like us,” Brown says.
Meanwhile, the body shape of H. floresiensis is in many ways more like the australopithecines than any human species. Her arms, which were discovered just a few weeks ago, are so long her hands reach almost to her knees. She has short legs with curved thigh bones and a small pelvis.
That doesn’t mean H. floresiensis and Australopithecus are closely related, Brown says. The shared features are more likely a function of small size. “At birth, their heads would have been the size of a lemon, about 15 per cent of the volume of a modern human baby’s. They didn’t need a broad, gynaecological pelvis,” Brown says.
But it’s the size of the skull that has most shocked anthropologists. It could not have contained a brain any bigger than a grapefruit – similar in size to a small chimpanzee’s brain – which raises the conundrum of how such a minuscule brain was capable of the sophisticated behaviour suggested by the discovery of tools and animal remains nearby. Mike Morwood, who co-directed the dig, points out the cut-off for the genus Homo used to be 500 cubic centimetres; yet H. floresiensis has a capacity of only 380 cc.
Indonesian archaeologists have dug the Liang Bua cave site for Neolithic human remains for the past 20 years, so at first the hominid’s small skull misled the excavation team. “We thought the skull and the mandible were from a child,” says excavation site director Thomas Sutikna of the Indonesian Centre for Archaeology, who was there when the initial discovery was made in September 2003. “The bone was very soft, so the excavation was very slow, very careful. But after a week, we checked the teeth and saw that they were already worn, and that the molars had erupted, so she was more than 20 years old. The team was very surprised. We sent a message to Mike [Morwood] to say we had found an important thing. I directly made a drawing of the skull and mandible and faxed it to Mike.”
The researchers say the skeleton was as soft as wet blotting paper when they found it. They left it to dry for several days, then added a commercially available glue called Tarzan’s Grip to harden the bone. Blocks of sediment containing the remains were then cut out and shipped to a lab in Ruteng in western Flores. From there, it was flown to Jakarta, where the skeleton now resides at the Indonesian Centre for Archaeology.