The discovery of additional bones in an Indonesian cave supports a stunning claim made last year that a new species of a very small hominid existed at the same time as modern humans.
When Michael Morwood and Peter Brown of the University of New England in Armidale, New South Wales, and their team announced last October that they had found the partial skeleton of a meter-tall human in the cave of Liang Bua on the island of Flores, they raised a few eyebrows. Although the bones were tiny--particularly the skull, which had the brain volume of a chimpanzee--the teeth, jaw and cranium were described as similar to those of members of our own genus, Homo. The evidence, including stone tools, signs of fire and the bones of a dwarfed elephantlike beast, dated to about 18,000 years ago and prompted the scientists to assign the human remains to a new species, Homo floresiensis. Rebuttals ensued. Some proposed that the mini-human was a pygmy; others suggested that the skull came from a modern human who had suffered from microcephaly, a birth defect that results in a very small head.
Now Morwood, Brown and their colleagues say that various arm, leg, jaw, toe and finger bones as well as a scapula and vertebra were excavated in 2004, bringing the estimated number of individuals represented thus far at Liang Bua to nine and casting doubt on those alternative interpretations. Analysis of the second jaw shows that it is very similar to the first one. Both notably lack a chin, which is a unique characteristic of Homo sapiens, even those that suffer from microcephaly. And further study of the leg and arm bones confirm that H. floresiensis was about a meter tall and had long arms. Modern adult pygmies have legs and arms that are proportional to their short stature. "We can now reconstruct the body proportions with some certainty," the researchers write in the October 13 issue of Nature.
When the team published their first report on H. floresiensis, they proposed that it was a dwarfed descendant of Homo erectus, which may have arrived on the island hundreds of thousands of years earlier and evolved into a smaller being thanks to the lack of predators and limited resources. Flores already boasts species that have undergone this kind of evolution, such as giant rats and miniature elephant cousins that are now extinct. The new finds, however, have revealed similarities to the much older Australopithecus afarensis, which lived in Africa, underscoring the possibility that the tiny Flores people instead descended from an as yet unknown hominid more primitive than H. erectus. Thus, although H. floresiensis does appear to be a new species, the authors admit that its genealogy remains a mystery. But only a small portion of the site has been excavated and the scientists hope that further digging will reveal more answers.