Homo floresiensis: the Hobbit

Homo floresiensis is a species of dwarf human discovered at the Liang Bua cave on the Indonesian island of Flores in 2003 (Brown et al. 2004, Morwood et al. 2004, Lahr and Foley 2004). H. floresienses was only about 1 meter in height and fully bipedal, with a very small brain size of 417cc. The skull has human-like teeth with a receding forehead and no chin. floresiensis fossils have been discovered from 38,000 to 18,000 years ago, though archeological evidence suggests it lived at Liang Bua between at least 95,000 and 13,000 years ago. It used stone tools and fire, and hunted pygmy elephants (mostly juvenile ones), Komodo dragons, and the giant rats found on Flores. Its discoverers believe that floresiensis is a dwarf form of Homo erectus - it is not uncommon for dwarf forms of large mammals to evolve on islands.

The most complete floresiensis fossil, LB1, consists of an almost complete skull and a partial skeleton consisting of leg bones, parts of the pelvis, hands and feet, and some other fragments. LB1 was an adult of about 30, probably female judging by the pelvis. Males could have been larger, though the other fossils found so far indicate only individuals about the same size as LB1. Because of the damp condition and young age, the bones of LB1 have not fossilized (i.e. had not turned to stone), and reportedly had the consistency of mashed potatoes.

The brain size of the floresiensis skull is extraordinarily small, at 380cc. This is as small as any australopithecine ever discovered, and fairly typical for a chimpanzee. (Chimps range from about 300 to 500cc, averaging about 400cc, but are physically bigger than floresiensis.) This is smaller than would be expected even for a dwarf form of Homo erectus, and suggests there was active selection for a small brain size for some reason. (Human pygmies, incidentally, are nothing like H. floresiensis; their brains are almost as large as those of normal-sized humans)

There has been some speculation that the stone tools found with it were actually made by Homo sapiens, mainly because it is hard to believe a creature with such a small brain could make such sophisticated stone tools. There is no other evidence in support of this, however, and if it were not for the small brain size, there would be no hesitation about assuming floresiensis made the tools because of the close association between the tools and the fossils. The same tools are found through the entire deposit (from 90,000 to 13,000 years ago) and, interestingly, they are not like any stone tools made by Homo erectus.


Skull of LB1 compared
with a modern human Because evolving from erectus to floresiensis is such a drastic reduction in body size, there has been some speculation that floresiensis might actually have evolved from something smaller, such as the Dmanisi hominids found in Georgia, some of which have brain sizes between 600 and 700 cc, smaller than the 800-900cc typical of early erectus.

Flores was also in the news in 1998, when Mike Morwood (who is also involved with this new find) announced the discovery of stone tools at another site on Flores dated at 840,000 years. It was assumed at the time that this was evidence of Homo erectus, since erectus was the only pre-sapiens hominid known to have existed in Indonesia. Because Flores is thought to have always been separated from Java by a deep sea passage, this indicated a hitherto-unsuspected ability of H. erectus to cross sea barriers. The possibility now exists that the hominid responsible for this early archaeological evidence might not have been Homo erectus, but something else such as a Dmanisi hominid or a partly evolved form of floresiensis.

Modern humans arrived on Flores between 55,000 and 35,000 years ago, and presumably interacted with floresiensis, though there is no evidence of this at Liang Bua. However Indonesian folklore tells of creatures called Ebu Gogo which were small, inarticulate, and walked with an odd gait. This sounds remarkably suggestive of floresiensis, but it could easily be coincidence - if floresiensis had been found in Ireland, we'd possibly be wondering if they were leprechauns.

There is a possibility that DNA, particularly mitochondrial DNA (mtDNA), might be able to be retrieved from the bones. Their relatively recent age and the fact that the bones have not been been fossilized increases the likelihood that this can be done, but the tropical climate of Indonesia reduces the chance of success. High temperatures degrade DNA, and the Neandertal fossils from which mtDNA have been extracted all came from much colder climates than Indonesia. We will have to wait and see whether mtDNA can be successfully extracted from LB1. If so, it should prove very enlightening. (Some creationists are predicting that it will show floresiensis to be modern humans, but if, as Brown et al. believe, they descended from Homo erectus, the mtDNA of floresiensis should be even more different from modern humans than the Neandertals were.)

The discovery of H. floresiensis does not change the broad picture of human evolution, including our lineage - it was certainly not ancestral to us. But since it is the most extreme example of human adaptation ever found, it suggests that humans are more subject to evolutionary forces than we tend to think. And the fact that floresiensis lived so recently and yet has been unknown until now suggests that there could be other surprises waiting in the human family tree.

http://www.talkorigins.org/faqs/homs/flores.html