Nearly a decade after its discovery in Liang Bua cave on the Indonesian island of Flores, scientists are still debating just what Homo floresiensis, aka the Hobbit, really is. There’s still no clear answer, but new research presented at a conference in Germany hints at what H. floresiensis may not be.
Debbie Argue, a palaeoanthropologist at Australian National University in Canberra who led the study, says theories about the Hobbits’ origins fall into two categories. Some scientists say that H. floresiensis represents a dwarfed or diseased descendant of anatomically modern Homo sapiens. A second camp, to which Argue belongs, contends that the Hobbit is a dwarfed descendent of another ancient hominin species.
She thinks theories positing that the most complete floresiensis fossil, called LB1, represents an individual with some disease or pathology — microcephaly, dwarfism and cretinism have all been proposed — don’t hold water because LB1 is a poor match to the skeletons of contemporary humans with these conditions.
Certain features of H. floresiensis, such as the shape of its jaw bone, also discount the theory that the Hobbit is an evolutionarily dwarfed human, she says. Other animals, such as the pygmy hippopotamus, have evolved smaller bodies than their mainland ancestors, presumably to cope with a lack of food available on islands.
To determine which other human ancestor the Hobbit may have evolved from, Argue and her collaborators are in the process of comparing the features of LB1 to other hominin fossils. “We’ll put it all into an analysis and see what comes out,” she says.
At the European Society for the Study of Human Evolution conference in Leipzig, Germany on Friday 23 September, Argue presented a preliminary comparison to Homo erectus, the first human ancestor known to have migrated beyond Africa. The first H. erectus fossils were discovered on another Indonesian island, Java, and the species survived in Southeast Asia until about 50,000 years ago.
Argue pointed out a number of “striking differences” between H. erectus and H. floresiensis. The two species’ jaw bones, for instance, don’t resemble one another in profile. A bone that forms the brow-ridge, the supraorbital torus, also differs between the two species: H. erectus possess a massive bar that flares out, while the Hobbit’s is less pronounced. The two species’ dental anatomy also differ substantially, Argue says.
“It’s hard to envisage erectus being the ancestor of Homo floresiensis because there are so many differences,” she says, quickly adding that this conclusion is based on a visual comparison, not the quantitative comparisons her team have planned.
Another recent study found the H. floresiensis skull a poor match to H. erectus. But its authors interpreted this as evidence that H. floresiensis is a human that suffered from microcephaly and not another species of hominin.
If Argue’s hunch is correct, and the Hobbit doesn’t descend from H. erectus, just what is it? She and her colleagues favour earlier forms of Homo that tromped around Africa around 2 million years ago, such as Homo habilis and Homo rudolfensis, a point they made in a previous paper. But there are other possibilities. Perhaps, Argue says, H. floresiensis left Africa in its current form.
Australopithecus sediba, a 2-million-year old hominin recently discovered in South Africa, may even make a candidate as the ancestor of H. floresiensis, should it stand scientific scrutiny as a genuine new species, says Lee Berger, a palaeoanthropologist at the University of Witwatersrand in South Africa, whose team recently described A. sediba’s anatomy in a series of papers, identifying a mix of both primitive and modern, human-like traits. “Suddenly something like floresiensis doesn’t look so weird.”
Image of Homo floresiensis LB1 skull beside a modern human skull