Homo floresiensis

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Homo floresiensis ("Man of Flores") is a newly described species in the genus Homo, remarkable for its small body, small brain, and recent survival, thought to have been contemporaneous with modern humans (Homo sapiens) on the remote Indonesian island of Flores. Seven skeletons and associated stone tools were discovered on Flores in 2003.

Flores has been described (in the journal Nature) as "a kind of Lost World", where archaic animals, elsewhere long extinct, had evolved into giant and dwarf forms through allopatric speciation. The island had dwarf elephants (a species of Stegodon, the recent ancestor of the Indian Elephant) and giant lizards akin to the Komodo dragon, as well as H. floresiensis, which can be considered a species of dwarf human. The discoverers have called members of the diminutive species hobbits, after J.R.R. Tolkien's fictional race of roughly the same height.

Discovery

The first (and so far only) specimens were discovered by a joint Australian-Indonesian team of paleoanthropologists and archaeologists looking on Flores for evidence of the original human migration of H. sapiens from Asia into Australia. They were not expecting to find a new species, and were quite surprised at the recovery of the remains of at least seven individuals, from 95,000 to 12,000 years old, from the Liang Bua limestone cave on Flores.

The specimens are not fossilized, but were described in a Nature news article as being "the consistency of wet blotting paper." Researchers hope to find preserved mitochondrial DNA to compare with samples from similarly unfossilised specimens of Homo neanderthalensis and H. sapiens. The likelihood of there being preserved DNA is, however, low, as it degrades more rapidly in warm tropical environments; in such conditions it is known to degrade in as little as a few dozen years. Contamination from the surrounding environment seems highly possible given the moist environment in which the specimens were found.

Small bodies

Homo erectus, thought by the discoverers to be the immediate ancestor of H. floresiensis, was approximately the same size as another descendant species, modern humans. In the limited food environment on Flores, however, H. erectus is thought to have undergone strong island dwarfing, a form of speciation also seen on Flores in several species, including a dwarf Stegodon (a recent ancestor of the Indian elephant), as well as being observed on other small islands.

Despite the size difference, the specimens seem otherwise to resemble in their features H. erectus, known to be living in Southeast Asia at times coinciding with earlier finds of H. floresiensis. These observed similarities form the basis for the establishment of the suggested phylogenetic relationship. Despite a controversial reported finding by the same team of alleged material evidence of a H. erectus occupation 840,000 years ago, actual remains of H. erectus itself have not been found on Flores, much less transitional forms.

The type specimen for the species is a fairly complete skeleton and near-complete skull of a 30-year-old female about 1 metre (3 feet 3 inches) in height. Not only is this a drastic reduction compared to H. erectus, it is even somewhat smaller than the three million years more ancient ancestor Australopithecines, not previously thought to have expanded beyond Africa. This tends to qualify H. floresiensis as the most "extreme" member of the extended human family. They are certainly the shortest and smallest.

Homo floresiensis is also rather tiny compared to the modern human height and size of all peoples today. The estimated height of adult H. floresiensis is considerably shorter than the average adult height of even the physically smallest populations of modern humans, such as the African Pygmies (< 1.5 m, or 4 ft. 11 in.), Twa, Semang (1.37 m, or 4 ft. 6 in. for adult women), or Andamanese (1.37 m, or 4 ft. 6 in. for adult women). Mass is generally considered more biophysically significant than a one-dimensional measure of length, and by that measure, due to effects of scaling, differences are even greater. The type specimen of H. floresiensis has been estimated as perhaps about 25 kg (55 lb).

Homo floresiensis had relatively long arms, perhaps allowing this small creature to climb to safety in the trees when needed.

Inevitable comparisons with modern human achondroplasiacs (about 1.2 m, or 3 ft. 11 in.) or other dwarfs, are flawed, as these people are not generally proportionally smaller than other humans, only short-limbed.

Small brains

In addition to a small body size, H. floresiensis had a remarkably small brain. The type specimen, at 380 cm³(23 in³), is at the lower range of chimpanzees or the ancient Australopithecines. The brain is reduced considerably relative to this species' presumed immediate ancestor H. erectus, which at 980 cm³ (60 in³) had more than double the brain volume of its descendant species. Nonetheless, the brain to body mass ratio of H. floresiensis is comparable to that of H. erectus, indicating the species were unlikely to differ in intelligence. Indeed, the discoverers have associated H. floresiensis with advanced behaviors.

There is evidence of the use of fire for cooking. The species has also been associated with stone tools of the sophisticated Upper Paleolithic tradition typically associated with modern humans, who at 1310-1475 cm³ (80-90 in³) nearly quadruple the brain volume of H. floresiensis (with body mass increased by a factor of 2.6). Some of these tools were apparently used in the necessarily cooperative hunting of local dwarf Stegodon by this small human species.

Flores, because of a deep neighboring strait, remained isolated during the most recent ice age despite the low sea levels that united much of the rest of Sundaland. This has led the discoverers of H. floresiensis to conclude that the species or its ancestors could only have reached the isolated island by water transport, perhaps arriving in bamboo rafts around 100,000 years ago. This perceived evidence of advanced technology and cooperation on a modern human level has prompted the discoverers to hypothesize that H. floresiensis almost certainly had language. These suggestions have proved the most controversial of the discoverers' findings, despite the probable high intelligence of H. floresiensis.

Recent survival

The other remarkable aspect of the find is that this species is thought to have survived on Flores until at least as recently as 12,000 years ago. This makes it the longest-lasting non-modern human, long outsurviving the Neanderthals (H. neanderthalensis) who went extinct about 30,000 years ago. Homo floresiensis certainly coexisted with modern humans, who arrived in the region 35,000-55,000 years ago, for a long time, but it is unknown how they may have interacted.

Local geology suggests that a volcanic eruption on Flores was responsible for the demise of H. floresiensis in the part of the island under study at approximately 12,000 years ago, along with other local fauna, including the dwarf elephant Stegodon.

The discoverers suspect, however, that this species may have survived longer in other parts of Flores to become the source of the Ebu Gogo stories told among the local people. The Ebu Gogo are said to have been small, hairy, language-poor cave-dwellers on the scale of H. floresiensis. Widely believed to be present at the time of the Dutch arrival five hundred years ago, these strange creatures are said to have last been spotted just a century ago.

Similarly, on the island of Sumatra, there are reports of a one metre tall humanoid, the Orang Pendek, which a number of professional scholars take seriously. Both foot prints and hairs have been recovered. Scholars working on the Flores man have noted that the Orang Pendek may also be surviving Flores men still living on Sumatra.

Significance

The discovery is widely considered the most important of its kind in recent history, and came as a surprise to the anthropological community. The new species challenges many of the ideas of the discipline.

Homo floresiensis is so different in form from other members of genus Homo that it forces the recognition of a new, undreamt-of variability in that group, and reaffirms an intellectual trend away from the idea of linear evolution.

No doubt this discovery provides more fuel for the fire of the perennial debate over the out-of-Africa or multiregional models of the speciation of modern humans, despite H. floresiensis not itself being an ancestor of modern humans. Already, voices have been heard arguing it furthers either side.

The discoverers of H. floresiensis fully expect to find the remains of other, equally divergent Homo species on other isolated islands of Southeast Asia, and do not think it impossible, if not quite "likely", that some lost Homo species could be found still living in some unexplored corner of jungle.

Henry Gee, a senior editor of the journal Nature, has agreed, saying, "Of course it could explain all kinds of legends of the little people. They are almost certainly extinct, but it is possible that there are creatures like this around today. Large mammals are still being found. I don't think the likelihood of finding a new species of human alive is any less than finding a new species of antelope, and that has happened."

Reaction

Professor Teuku Jacob, chief paleontologist of the Indonesian Gajah Mada University and other scientists reportedly disagree with the placement of the new finds into a new species of Homo. "It is a sub-species of Homo sapiens classified under the Austrolomelanesid race," he said. He will attempt to prove that the find is from a 25-30 year-old omnivorous subspecies of H. sapiens, and not a 30-year-old female of a new species. He is convinced that the small skull is that of a mentally defective human.

Some scientists reportedly believe the skeleton found may be of a male and not a female and the subject may have been suffering from the disease microcephaly. When interviewed on the Australian television program Lateline, Professor Roberts reportedly conceded that the skeleton may be that of a male rather than a female but he strenuously maintained the fossil is of a new species.

References

Homo floresiensis was first described in two papers which appeared in the journal Nature, a year after the discovery:

Brown, P., et al. "A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia." Nature 431: 1055-1061 (October 27 2004)
Morwood, M. J., et al. "Archaeology and age of a new hominin from Flores in eastern Indonesia." Nature 431: 1087-1091 (October 27 2004)