Athena Review, Vol. 4, No. 2
It sounds like a fairy tale: on an isolated island, far, far, away lived a race of tiny human-like creatures who battled dragons and hunted miniature elephants. Yet discoveries by Australian researchers Peter Brown and Michael Morwood of the University of New England and their Indonesian colleagues (2004) may indicate that this actually happened. In Oct. 2003, in Liang Bua cave on the island of Flores in eastern Indonesia (fig.1,2), they discovered a skull and skeletal remains of tiny hominins in levels 5.9 m below the cave floor (dated 95,000-13,000 ya), with bones of kimodo dragons and dwarf elephants called Stegadons. Stone tools including blades and points were found in another part of the cave. Size and other anatomical characteristics of the small hominins (nicknamed "hobbits") appeared so distinct from modern humans that Brown and Morwood have proposed a new species identification, Homo floresiensis.
According to the Australian researchers, the single skull (called LB-1 for Liang Bua 1), which they identified as female, resembles Homo erectus more than modern Homo sapiens. although it has a highly anomalous, diminutive brain size of only 380 cm3, half that of the Javanese Homo erectus of 1.7 to .8 million years ago (mya). Indeed, it is smaller than that of any ancestral hominin, including australopithecines of 4-3 mya, and is of a size comparable only to pathologically small braincases. The cranial volume to body ratio is also outside the accepted hominin range, and indicates that, unlike modern dwarfs or pygmies, the brain of the Flores "hobbit" was proportionally smaller than the body.
[ Fig.1: Indonesia and the Islands of Java and Flores, showing the Sunda shelf exposed during the Lower Pleistocene. Dashed line marks the "Wallace Line"].
Another surprising factor, in light of the proposed species distinction, is the dating of the purportedly Homo erectus-linked individual to about 18,000 years ago - thousands of years after H. sapiens had colonized the neighboring region (55-35 kyr.) Based on unpublished postcranial remains identified as members of the same species, the Australian researchers propose Homo floresiensis lived on Flores up to 12,000 years ago, when life on the island was disturbed by a volcanic eruption.
In the immediate background of the "hobbit" discoveries are proposed connections between Homo erectus and the island of Flores, researched by several independent groups. For half a century, excavations have been carried out at Liang Bua ("cold cave"), which overlooks a valley of waterlogged paddy fields (fig.2). Liang Bua was first investigated in the 1950s by Dutch missionary Theodoor Verhoeven, who found extinct Stegadon bones in levels with stone tools (fig.3). He reported these in a 1968 Anthropos article as dating from 750,000 year old Homo erectus occupations on Flores.
Indonesian archaeologists performed further excavations at Liang Bua in the 1980s. Geomagnetic dating of volcanic layers with stone tools and Stegadon fossils, led by Paul Sondaar (1994), basically confirmed dates in the Homo erectus era of about 800,000 years ago which Verhoeven had first proposed.
A few years later, using fission-track dating, Morwood and his colleagues obtained similar dates on Flores of around 800,000 BC for volcanic layers associated with Stegadon fossils and flake tools. To account for the tools, Morwood et al (1998) proposed that H. erectus rafted to the island by 840,000 ya. This theory was not universally accepted, since at least 25 km of open water had to be crossed from islands such as Sumbawa near Bali (Gibbons 1998; see AR 2,1). In response, Morwood et al proposed that "the cognitive capabilities of H. erectus may be due for reappraisal."
Linking their latest findings of the diminutive Flores hominin to this rafting hypothesis, Morwood, Brown et al propose that the "hobbits" evolved as an end product of Homo erectus immigrants who originated in Java ca. 850,000 ya. These would have been roughly contemporary with the Trinil 2 or Sangiran 17 fossil hominins, whose body sizes were near those of modern humans, and whose cranial capacities of about 800-900 cc were typical of ancestral hominins everywhere at that time (see AR 4,1).
According to Brown, Morwood et al, the Homo erectus on Flores then gradually shrank to Lilliputian dimensions over the next 750,000 years, in a process of dwarfism never before observed in humans, but seen in some mammals such as the dwarf Stegadon, on isolated islands where scarce resources and lack of predators favors smaller body mass. At the same time, the gigantic lizards on Flores called Komodo Dragons apparently increased in size due to the same island conditions.
If Brown and Morwood's hypotheses about the origin of H. floresienses are correct, this would be the first evidence that humans have been subject to the same endemic dwarfing forces as observed in other mammals. It would then indicate that the genus Homo is morphologically more variable and flexible in its adaptive response than previously believed. It could be possible that other heretofore unknown human species are still out there waiting to be found, a situation that corresponds with the "Replacement" model of hominin evolution, which proposes periodic speciation events due to isolation of populations.
In contrast, the existence of a recent but distinct Homo species that evolved in isolation and did not contribute to the genetic make-up of modern humans clearly goes against the multiregional hypothesis. This theory postulates that Homo sapiens gradually evolved as a single species from worldwide populations of Homo erectus interbreeding over the past 1.9 million years (see AR 4,1). The opposing "Recent Out of Africa" or Replacement theory, meanwhile, states that H. sapiens evolved as a distinct and relatively recent species in Africa, and then spread throughout the world after 100,000 years ago, replacing all other hominins including Neanderthals, Homo soloensis, and other late Homo erectus offshoots.
[Fig.2: The western part of Flores, showing the location of Liang Bua Cave (after Morwood et al 2004)].
One basic tenet of the "Replacement" theory - that Homo erectus did not lead to modern humans - is directly bolstered by the findings of Brown and Morwood, which suggest that Javan Homo erectus isolated in Flores led instead to the diminutive, small-brained species called Homo floresiensis. Yet other implications of the Flores find may not fit so neatly into the "Recent out of Africa" camp. As Morwood pointed out in an interview late in 2004, more complex evolution of the Homo species may have occurred in southeast Asia, of which Homo floresiensis may be only the tip of the iceberg.
Some scientists favoring multiregional continuity are citing evidence for pathology in the Flores skeleton. Maciej Henneberg, a paleopathologist at the University of Adelaide, Australia, has compared the Flores skull to a 4000-year-old microcephalic modern human skull from the Minoan period in Crete. A statistical comparison of fifteen head and face dimensions of the LB-1 specimen with those of the Minoan microcephalic showed no points of significant differences between the two skulls.
In response, a CT (computer tomography) scan of the Liang Bua skull (Falk et al 2005) yielding "virtual" evidence of a cranial endocast of the brain region, appears to support the theory that LB-1 is a separate species. [Readers may note, however, that Brown et al's (2004) report cautioned that cranial vault sutures and other potential endocast markers were seriously damaged in the skull when it was excavated in 2003.]
The sample size at Liang Bua is also an issue. Brown and Morwood asserted in informal news interviews that at least seven diminutive individuals were found at the Flores site, and that all represent the new species, Homo floresiensis. Yet in the 2004 Nature article which presented the new species definition, only two other human fossils were reported besides the holotype skeleton called LB-1. These include a single premolar, and a forearm bone (radius) found deeper down in Liang Bua cave. The forearm, based on its dimensions was claimed by Brown et al (2004) as further proof that a local population existed of diminutive Homo floresiensis. Yet, as Henneberg points out, the reported length of the radius of 210 mm actually corresponds to human stature of 151-162 cm, within the range of many modern women and some men. This view is seconded by Alan Thorne, formerly of the Australian National University in Canberra, who has proposed some early Australian aboriginal fossil remains are descended from Homo soloensis or "Solo Man," the late Homo erectus offshoot from Java.
Also taking the view that the Flores skeleton is from a diminutive modern human is Indonesian professor Teuku Jacob, chief paleontologist from the state Gajah Mada University. Jacob, who has supervised work in Java on both Homo erectus and "Solo Man" sites, is convinced that the Flores hominin is not a new species, and that the small skull of LB-1 is related to microcephaly. Jacob believes the bones represent a pygmy version of Homo sapiens, part of an Australomelanesid group including many small individuals. Small people are not uncommon in the region today. Pygmies still live in the Andaman and Nicobar islands, in western Papua, and the Philippines, as well as on Flores. Some village people on Flores originate from the island of Kalimantan (formerly Borneo) - where pygmy-sized people also live.
[Fig 3: Three of the stone tools found in Liang Bua cave on the same level as the hominin called LB-1 ( both front and edge views are shown: a) microblade; b)scraper; c) large blade (after Morwood et al 2004)].
In April 2005, Indonesian researchers reported the existence of a pygmy community only about 1km from the Liang Bua cave, in the village of Rampapasa (Kompas Daily, 29 Apr. 2005). The village currently contains some seventy-seven pygmy families, comprising about 80% of the Rampapasa villagers, with most male adults under 145cm (4 ft, 7 in), and female adults about 135cm (4 ft 4 in). The hobbit skeleton would have belonged to an individual who stood about 3-foot 5-inches. Brown, Morwood and their colleagues, meanwhile, have begun testing on Java for further evidence of extinct populations of Homo floriensis.
[Brown, P. et al 2004 "A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia." Nature 431:1055-1061; Morwood, M. et al 2004. "Archaeology and age of a new hominin from Flores in eastern Indonesia." Nature 431:1087-1091; Falk, D. et al 2005. "The Brain of LB1, Homo floressiensis" Science 308:242-245; Morwood, M. et al 1998. "Fission-track ages of stone tools and fossils on the east Indonesian island of Flores." Nature 392:173-176]; Kompas Daily (Indonesia), 29 April 2005]
This article appears on pages 5-6 in the Recent Finds in Archaeology of Vol.4 No.2 of Athena Review. The complete text may be obtained in the printed version of the magazine.
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