This thesis investigated whether a fragmented assemblage of fossilized Homo
sapiens remains collected from Palau; Micronesia represents a population exhibiting a case
of insular dwarfing. The earliest occupation of Palau is ca. 4000 YBP, and the fossil
assemblage studied here dates between 2900 – 1400 YBP, thus providing a relatively short
time in which body size reduction, due to insular dwarfism could occur. There are well
known cases, in both the modern and fossil context, where insular dwarfism and body size
reduction is known to occur in human populations that are isolated, but the results of this
reduction are seen over a much longer period (e.g., tens of thousands of years).
Metric dimensions of the humerus, radius, ulna, femur, tibia, and fibula and os coxa are
quantified in order to evaluate other potential insular dwarfs in fossil hominin assemblages,
such as Homo floresiensis.
Previous studies have shown that the Palau archipelago has remained relatively
isolated from human contact due to the surrounding currents, providing ideal conditions for
insular dwarfism to occur. Comparing measurements taken on populations encompassing a
reasonable range of human variation, this study quantified and compared the Palauan
measurements and joint ratios to determine which variables might differentiate among
these population groups, thus indicating traits potentially uniquely signalling a reduction in
human body size.
Disproportionate joint sizes were observed in the humerus, ulna, tibia, and femur of
the Palauan sample. While individual measurements from the Palau sample all fall
comfortably within the range of measurements taken from other small-bodied human
individuals, the articular surfaces of Palauan specimens do not resemble those from other
well-established, small-bodied insular populations. As the articular surfaces are smaller
relative to the epiphyseal diameters and may be a reflection of the relatively short time in
which the reduction has taken place.
Morphologically the Palauan population exhibits small orbits, a large interorbital
distance, an inflated glabella region and protruding supraorbital tori. A reduction in the
mandible may account for the overcrowding of teeth observed in the dentition. The
Palauan individuals have disproportionately large maxillary teeth. The mandibular
dentition, however, varies: the incisors, canine and first molars are large, while reduction is
seen most easily in the premolars and the second molar. This dental reduction is coupled
with significant differences between the cervico-enamel junctions for these teeth and the
corresponding crown measurements. Large teeth, inflated glabella, and protruding
supraorbital tori may be an indication of a founding population. These traits are all found
in Australomelanesian populations, and it is thus possible that the Palauan population
under study originated from Melanesia (e.g. New Guinea or South East Asia).
Application of the present study to Homo floresiensis, a fossil hominin suggested
by some authors to have undergone insular dwarfing, reveals that while H. floresiensis is
small for some measurements, most fall within the range of the small-bodied comparative
sample from Palau. The stature of H. floresiensis is not unusually small and falls within the
ranges of the comparative sample used here. The only comparison that can be made for joint size is that both the Palauan and H. floresiensis femoral heads are small and both
exhibit the same disproportionate dimensions of the proximal tibia. As potential body size
reduction is possibly responsible for the Palauan traits, the similarity in joint proportions
may be attributed to insular dwarfing when the population first became isolated, as these
joint irregularities are not seen in established insular dwarfs (Andaman and Nicobarese).
The differences present in the measurements obtained for all the small-bodied samples
examined suggests that even though insular populations may present as small-bodied, the
island populations (fossil or extant) should be viewed as a case by case study. Isolation,
life history, founding population (genetics) and environmental conditions all affect
population body size over time, but to assume that all isolated populations will decrease
body size in the same way is incorrect. What is seen in Palauan specimens is likely the
adaptive responses of a isolated population from Melanesia, resulting in the insular
dwarfism observed. By examining the available aspects of this insular population and
found that it was consistent in reflecting size and proportions of small-bodied populations.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/12364 |
| Date | 01 February 2013 |
| Creators | De Klerk, Bonita |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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