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Homo floresiensis

2007 Schools Wikipedia Selection. Related subjects: Mammals

                   iHomo floresiensis
   Homo floresiensis cranium. On the cover of Nature.
   Homo floresiensis cranium.
   On the cover of Nature.

                             Conservation status

   Prehistoric
               Scientific classification

   Kingdom: Animalia
   Phylum:  Chordata
   Class:   Mammalia
   Order:   Primates
   Family:  Hominidae
   Genus:   Homo
   Species: H. floresiensis

                                Binomial name

   †Homo floresiensis
   P. Brown et al., 2004

   Homo floresiensis ("Man of Flores") is the proposed name for a possible
   species in the genus Homo, remarkable for its small body, small brain,
   and survival until relatively recent times. It is thought to have been
   contemporaneous with modern humans (Homo sapiens) on the Indonesian
   island of Flores. One largely complete sub-fossil skeleton (LB1) and
   one molar (LB2), dated at 18,000 years old, were discovered in deposits
   in Liang Bua Cave on Flores in 2003. Parts of seven other individuals
   (LB3 – LB9, the most complete being LB6), all diminutive, have been
   recovered as well as similarly small stone tools from horizons ranging
   from 94,000 to 13,000 years ago.

   The first of these fossils was unearthed in 2003 and the publication
   date of the original description is October 2004. Confirmation of
   species status was expected to appear in March 2005, following
   publication of details of the brain of Flores Man in Science. However,
   several other researchers have argued that the original specimen does
   not represent a new species, but rather a modern H. sapiens with
   microcephaly. The original discoverers and others have argued against
   these interpretations and maintain that H. floresiensis is a distinct
   species. To date, the only complete cranium is that of LB1, and
   additional skeletons may be required to resolve this debate.
   Regardless, the discovery is widely considered the most important of
   its kind in recent history, and came as a surprise to the
   anthropological community.

Discovery

   ██ Flores is the westernmost large island in the group of islands shown
   in yellow.
   Enlarge
   ██ Flores is the westernmost large island in the group of islands shown
   in yellow.

   The first 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 nearly complete skeleton of a
   hominid they dubbed LB1 (for the first skeleton recovered at the Liang
   Bua Cave). Subsequent excavations recovered seven additional skeletons,
   dating from 38,000 to 13,000 years old, from Liang Bua limestone cave
   on Flores. An arm bone, provisionally assigned to H. floresiensis, is
   about 74,000 years old. Also widely present in this cave are
   sophisticated stone implements of a size considered appropriate to the
   1 m tall human: these are at horizons from 95,000 to 13,000 years and
   are associated with juvenile Stegodon, presumably the prey of LB1.

   The specimens are not fossilized, but were described in a Nature news
   article as having "the consistency of wet blotting paper" (once
   exposed, the bones had to be left to dry before they could be dug up).
   Researchers hope to find preserved mitochondrial DNA to compare with
   samples from similarly unfossilised specimens of Homo neanderthalensis
   and H. sapiens. It is unlikely that useful DNA specimens exist in the
   available sample, as DNA degrades rapidly in warm tropical
   environments, sometimes in as little as a few dozen years. Also,
   contamination from the surrounding environment seems highly possible
   given the moist environment in which the specimens were found.

Anatomy

   In their initial reports, Peter Brown, Michael Morwood, and their
   colleagues argued that a variety of features, both primitive and
   derived, identified the skeleton of LB1 as that of a new species of
   hominin, H. floresiensis. The most important and obvious of these
   features are the small body and small cranial capacity of LB1. Brown
   and Morwood also identified a number of additional, less obvious
   features, that might distinguish LB1 from modern H. sapiens, including
   the form of the teeth, the absence of a chin, and the unusually low
   twist in the forearm bones. Each of these putative distinguishing
   features has been heavily scrutinized by the scientific community, with
   different independent research groups reaching differing conclusions
   whether these features support the original designation of a new
   species, or whether they identify LB1 as a severely pathological H.
   sapiens. The discovery of additional partial skeletons have verified
   the existence of some features found in LB1, such as the lack of a
   chin, but Jacobs and colleagues argue that these features do not
   distinguish LB1 from local H. sapiens morphology.

Small bodies

   The type specimen for the proposed species is a fairly complete
   skeleton and near-complete skull proposed to be that of a 30-year-old
   female (LB1), nicknamed Little Lady of Flores or Flo, about 1.06 m
   (3 ft 6 in) in height. This short stature is also supported by the
   height estimates derived from the tibia of a second skeleton (LB8), on
   the basis of which Morwood and colleauges suggest that LB8 might have
   stood 1.09 m (3 ft 7 in) high. These estimates are outside the range of
   normal modern human height and 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. LB1 has been estimated as perhaps about 25 kg (55  lb). This
   is smaller than not only modern H. sapiens, but also than H. erectus,
   which Brown and colleagues have suggested is the immediate ancestor of
   H. floresiensis. LB1 and LB8 are also somewhat smaller than the three
   million years older ancestor australopithecines, not previously thought
   to have expanded beyond Africa. Thus, LB1 and LB8 may be the shortest
   and smallest members of the extended human family discovered thus far.

   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 purported to be 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, stone tools, 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.

   To explain the small stature of H. floresiensis, Brown and colleagues
   have suggested that in the limited food environment on Flores H.
   erectus underwent strong insular dwarfism, a form of speciation also
   seen on Flores in several species, including a dwarf Stegodon (a group
   of proboscideans that was widespread throughout Asia during the
   Quaternary), as well as being observed on other small islands. However,
   the "island dwarfing" theory has been subjected to some criticism from
   Teuku Jacob and colleagues who argue that LB1 is similar to local
   Rampasasa H. sapiens populations, and who point out that size can vary
   substantially in pygmy populations.

Small brains

   The skull of H. floresiensis.
   Enlarge
   The skull of H. floresiensis.

   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 estimated
   brain to body mass ratio of LB1 lies between that of Homo erectus and
   the great apes.

   Indeed, the discoverers have associated H. floresiensis with advanced
   behaviors. There is evidence of the use of fire for cooking in Liang
   Bua cave, and evidence of cut marks on the Stegodon bones associated
   with the finds. 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.

   An indicator of intelligence is the size of region 10 of the
   dorsomedial prefrontal cortex, which is associated with self-awareness
   and is about the same size as that of modern humans, despite the much
   smaller overall size of the brain.

Additional features

   Additional features used to argue that the finds come from a population
   of previously unidentified hominins include the absence of a chin, the
   relatively low twist of the arm bones, and the relative width of the
   leg bones relative to their length. The presence of each of these
   features has been confirmed by independent investigators but their
   significance has been disputed. For example, Jacob and colleagues argue
   that each of these unusual features indicates some form of pathology in
   the LB1 skeleton.

Recent survival

   The species is thought to have survived on Flores until at least as
   recently as 12,000 years ago making it the longest-lasting non-modern
   human, surviving long past the Neanderthals (H. neanderthalensis) which
   became extinct about 29,000 years ago. Homo floresiensis certainly
   coexisted for a long time with modern humans, who arrived in the region
   35,000–55,000 years ago, but it is unknown how they may have
   interacted.

   Flores remained isolated during the Wisconsin glaciation (the most
   recent glacial period), despite the low sea levels that united much of
   the rest of Sundaland, because of a deep neighboring strait. 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
   (or, if they are H. erectus, then about 1 million 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 been
   some of the most controversial of the discoverers' findings, despite
   the probable high intelligence of H. floresiensis.

   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 arrival of the first
   Portuguese ships during the 16th century, these strange creatures were
   apparently last spotted as recently as the late 19th century.

   Similarly, on the island of Sumatra, there are reports of a 1-1.5 m
   tall humanoid, the Orang Pendek, which a few professional scholars,
   such as Debbie Martyr and Jeremy Holden, take seriously. Footprints and
   hairs believed to be from the Orang Pendek have been recovered by two
   amateur explorers. Analysis of these have yielded mixed results; both
   footprints and hairs are believed to originate from a previously
   undocumented species of primate but DNA analysis of the hairs found
   only human DNA. A possible explanation for this is that contamination
   by people who handled the hairs could have introduced this DNA and the
   original DNA could have decomposed. Scholars working on the Flores Man
   have noted that the Orang Pendek may also be surviving Flores men still
   living on Sumatra.

Controversies

   Whether the specimens represent a new species is a controversial issue
   within the scientific community. In 2005, a computer-generated model of
   the skull of Homo floresiensis provided further support that the
   controversial specimens from Indonesia do indeed represent a new
   species. The study of the creature's brainpan showed that it was
   neither a pygmy nor an individual with a malformed skull and brain, as
   some critics contend, lending support to the discovery team's assertion
   that the metre-tall specimen belongs to a species distinct from Homo
   erectus. These results continued to be debated.

   In the May 19, 2006, issue of the journal Science, Robert D. Martin of
   the Field Museum in Chicago and some co-authors argued that the fossil
   of Homo floresiensis appears to be that of a modern human with
   microencephaly, a disorder resulting in a small brain and other
   defects. Martin argued that the brain is far too small to be a separate
   dwarf species; if it were, he wrote, the 400-cubic-centimeter brain
   would indicate a creature only one foot in height, which would be
   one-third the size of the discovered skeleton.

   In the September 5, 2006, issue of the Proceedings of the National
   Academy of Sciences, a group of scientists from Indonesia, Australia,
   and the United States came to the same conclusion as Dr. Martin by
   examining bone and skull structure. In response, several
   paleontologists have criticized the findings by claiming that the
   scientists came to incorrect conclusions about skull structure and
   mistakenly attributed the height of Homo floresiensis to
   microencephaly.

   Professor Teuku Jacob, chief paleontologist of the Indonesian Gadjah
   Mada University and other scientists reportedly disagree with the
   placement of the new finds into a new species of Homo, stating instead,
   "It is a sub-species of Homo sapiens classified under the
   Austrolomelanesid race". He contends 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 modern human, probably a Pygmy, suffering from
   the genetic disorder microcephaly or nanocephaly (now discounted).
   Professor Jacob borrowed most of the remains from Soejono's
   institution, Jakarta's National Research Centre of Archaeology, for his
   own research (apparently without the permission of the Centre's
   directors). Some expressed fears that, like the Dead Sea Scrolls,
   important scientific evidence would be sequestered by a small group of
   scientists who neither allowed access by other scientists nor published
   their own research. However, Jacob returned the remains to the Centre,
   with the exception of two leg bones, on 23 February 2005.

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