Michael Pietrusewsky

Australian Tooth-Size Clines and the Death of a Stereotype [and Comments and Reply]

Tooth size in Australia ran from a minimum in the Cape York Peninsula of northern Queensland to a maximum in the Murray Basin. The available data suggest that the earliest Australians possessed large jaws and teeth and that subsequently genes for smaller tooth size entered Australia from the northeast corner a model which is consistent with the evidence for the spread of a variety of cultural and technological items. While the evidence is tentative at best, it is consistent with the view that more developed food-preparation techniques had ocurred outside of Australia, allowing dental reduction to occur. The spread of these elements into Australia may be symbolized by the influx of the small-tool tradition early in the Holocene, and it may have been made possible by associated resource-utilization techniques that promote survival in areas previously sparsely utilized, such as the central desert and the coastal margins. This would account for the tooth-size gradient visible down the east coast and from Cape York to the western desert. The largest teeth in Australia survived in just those areas most favorable to human habitation where one would expect the genetic contribution of the earliest inhabitants to be most prominently represented. Tasmanian affinities are clearly with southeastern Australia. After initial occupation, Australia was subject to a continuous trickle of cultural-biological influence from the north rather than having been the receptacle for specific waves, migrations, or invasions.

Optimal Ancient DNA Yields from the Inner Ear Part of the Human Petrous Bone

The invention and development of next or second generation sequencing methods has resulted in a dramatic transformation of ancient DNA research and allowed shotgun sequencing of entire genomes from fossil specimens. However, although there are exceptions, most fossil specimens contain only low (~ 1% or less) percentages of endogenous DNA. The only skeletal element for which a systematically higher endogenous DNA content compared to other skeletal elements has been shown is the petrous part of the temporal bone. In this study we investigate whether (a) different parts of the petrous bone of archaeological human specimens give different percentages of endogenous DNA yields, (b) there are significant differences in average DNA read lengths, damage patterns and total DNA concentration, and (c) it is possible to obtain endogenous ancient DNA from petrous bones from hot environments. We carried out intra-petrous comparisons for ten petrous bones from specimens from Holocene archaeological contexts across Eurasia dated between 10,000-1,800 calibrated years before present (cal. BP). We obtained shotgun DNA sequences from three distinct areas within the petrous: a spongy part of trabecular bone (part A), the dense part of cortical bone encircling the osseous inner ear, or otic capsule (part B), and the dense part within the otic capsule (part C). Our results confirm that dense bone parts of the petrous bone can provide high endogenous aDNA yields and indicate that endogenous DNA fractions for part C can exceed those obtained for part B by up to 65-fold and those from part A by up to 177-fold, while total endogenous DNA concentrations are up to 126-fold and 109-fold higher for these comparisons. Our results also show that while endogenous yields from part C were lower than 1% for samples from hot (both arid and humid) parts, the DNA damage patterns indicate that at least some of the reads originate from ancient DNA molecules, potentially enabling ancient DNA analyses of samples from hot regions that are otherwise not amenable to ancient DNA analyses.

An assessment of health and disease in the prehistoric inhabitants of the Mariana Islands

Using a variety of skeletal and dental stress indicators, an assessment of the health and disease of the indigenous inhabitants of the Mariana Islands, the Chamorro, is made. The major hypothesis to be tested is that the Chamorro were relatively healthy and that deviations from the expected, as well as inter-island variation, may reflect environmental, ecological, and cultural differences. The major skeletal series surveyed include sites on Guam (N = 247 individuals), Rota (N = 14), Tinian (N = 20), and Saipan (N = 102). The majority of the specimens are from the transitional pre-Latte (AD 1-1000) and Latte (AD 1000-1521) periods. These data derive primarily from unpublished osteological reports. The indicators of health and disease surveyed include mortality and paleodemographic data, stature, dental paleopathology, cribra orbitalia, limb bone fractures, degenerative osteoarthritis, and infectious disease (including treponemal infection). Where appropriate, tests of significance are calculated to determine the presence of any patterning in the differences observed within and between the skeletal series. Information recorded in prehistoric Hawaiians provides a standard for external comparisons. Several of the larger skeletal series surveyed have paleodemographic features that are consistent with long-term cemetery populations. Females and subadults are typically underrepresented. Most subadult deaths occur in the 2-5 year age interval. Life expectancy at birth ranges from 26.4 to 33.7 years. A healthy fertility rate is indicated for these series. The prehistoric inhabitants of the Mariana Islands were relatively tall, exceeding living Chamorros measured in the early part of the present century. The greater prevalence of developmental defects in the enamel suggests that the Chamorro were exposed to more stress than prehistoric Hawaiians. The low frequency of cribra orbitalia further indicates iron deficiency anemia was not a problem. There are generally low frequencies of dental pathology in the remains from the Mariana Islands. Betel-nut staining is relatively common in all series which may help to explain the relatively low prevalence of dental pathology. Healed limb bone fractures are rare in these skeletal series; the frequency and patterns of fractures suggest accidental injury as the main cause. Greater physical demands involving the lower back region are indicated by a high frequency of spondylolysis, or stress fracture in the lumbar vertebrae in the Chamorro. Likewise, advanced degenerative bone changes, while of low occurrence, are significantly greater in the Chamorro than Hawaiians. The prevalence of skeletal and dental indicators of stress was generally higher in the smaller islands of the Mariansas chain (e.g., Rota), islands with fewer resources to buffer environmental catastrophe. Bony changes suggestive of treponemal (probably yaws) disease are common in most of these Marianas Islands skeletal series.

Matrilocality during the prehistoric transition to agriculture in Thailand

Stable isotopes in teeth are providing important correlations between ancient people and the geographical location of their childhood homes. In an exciting new application, the authors measured the varying signatures of strontium, oxygen and carbon isotopes in the teeth of a sequence of people buried in Thailand during the period of the introduction and intensification of agriculture. Preliminary results point to the arrival of immigrant men, followed by a change in the relationship between the sexes: the women grow up on local food, the men have access to more widespread resources. This perhaps implies a matrilocal system, where forager men raised elsewhere marry into farming communities. It provides a likely antithesis to the social consequences of introducing agriculture into central Europe.

The Supraorbital Torus: "A Most Remarkable Peculiarity" [and Comments and Replies]

The supraorbital torus is found only in some genera of the primate order. Because no muscles of consequence attach directly to it, it has been considered nonfunctional. However, invitro strain-gauge experiments demonstrate that when the anterior teeth are loaded, the supraorbital region acts as a bent beam, pulled downward on each end by masticatory muscle forces and pushed upward centrally by bite force. Clinical and experimental data indicate that in response to repeated dynamic bending stress, adaptive cellular activity reconstructs skeletal material until bending stresses are neutralized. With these facts in mind, the hypothesis that supraorbital development is, in part, a predictable ontogenetic response to in-vivo bending stresses which concentrate over the eyes during anterior tooth loading was tested by means of a biomechanical model. The bent-beam model states that supraorbital bending is a function of the area moment of inertia of the forehead (relative to the direction of the bite force) and of the bending moment. When this model was tested on a series of Australian Aboriginal crania, significant relationships were found between browridge development and measures of forehead area moment and bending moment. It was concluded that the torus functions to resist bending stress concentrated over the eyes during anterior biting and that its development is proportional to the amount of such stress which cannot be resisted by the unadorned frontal bone.

Skeletal biology of Apurguan: A precontact Chamorro site on Guam

The human skeletal remains of a minimum of 152 individuals from the precontact Latte Period (AD 1000-1521) on Guam, Mariana Islands, are described. The sample, recovered at Apurguan, in the Tamuning District, is one of the largest series of well-provenienced Chamorro skeletal remains to be analyzed in recent years. The size and systematic nature of this database are a major contribution to the human biology of the region. Paleodemographic characteristics, dental and skeletal morphology, and paleopathology are presented, along with a limited examination of sex differences in frequencies of nonmetric variation. The mortuary sample, consisting of 51 subadults and 101 adults, exhibits underrepresentation of females, highest subadult mortality between 2 and 10 years, and an adult average age-at-death of 43.5 years. Cranial and infracranial indices and nonmetric variation are consistent with the Chamorros Southeast Asian origins. There are few statistically significant sex differences in nonmetric variation which suggests close genetic affinity. The frequency of dental pathology overall is low, reflecting a well-balanced, varied diet, and consistent with preagricultural subsistence; however statistically significant sex differences suggest the influence of differential cultural behaviors or resource access. Paleopathological observations include healed fractures (more common in males), little advanced osteoarthritis, evidence for gouty arthritis, and treponemal disease (yaws). One individual, a young adult male, was interred with 10 human bone spear points in situ. Twenty percent of the primary burials exhibit evidence of postdepositional removal of selected skeletal elements for cultural purposes such as keepsakes or raw material.

Intensification of Agriculture at Ban Chiang: Is There Evidence from the Skeletons?

Human skeletal remains excavated in 1974 -1975 at Ban Chiang, a premetal to Bronze/Iron Age site located in northeastern Thailand, are used to examine the health effects of sedentism and agricultural intensification. The archaeological sequence provides evidence for the introduction of iron and water buffalo in the Middle period, suggesting the beginning of intensified agriculture. The effects of this agricultural intensification on the paleodemography, health, and patterns of traumatic injury of Ban ChiangÕs early inhabitants is examined. The skeletal and dental attributes examined include palaeodemographic parameters, dental caries, dental enamel hypoplasia, cribra orbitalia, stature, skeletal infections, and trauma. The results of this analysis are mixed. There are decreases in life expectancy and mean age-at-death that are consistent with a decline in health over time, but evidence for an increase in fertility, expected with intensified agriculture, is not found. Expected temporal increases in dental enamel hypoplasia and adult cribra orbitalia are documented. However, the expected decline in adult stature and expected increases in dental caries, cribra orbitalia in subadults, skeletal infection, and traumatic injury are not found. Overall, the skeletal indicators support continuity in Ban Chiang health, suggesting continuous reliance on a broadly based subsistence system. These findings do not fit the typical pattern demonstrated for other human groups experiencing the transition to sedentism and intensified agriculture and may support the contention that Southeast AsiaÕs archaeological sequence differs markedly from those studied elsewhere in the world.

From the Mouths of Babes: Dental Caries in Infants and Children and the Intensification of Agriculture in Mainland Southeast Asia

Many bioarchaeological studies have established a link between increased dental caries prevalence and the intensification of agriculture. However, research in Southeast Asia challenges the global application of this theory. Although often overlooked, dental health of infants and children can provide a sensitive source of information concerning health and subsistence change. This article investigates the prevalence and location of caries in the dentition of infants and children (less than 15 years of age) from eight prehistoric mainland Southeast Asian sites collectively spanning the Neolithic to late Iron Age, during which time rice agriculture became an increasingly important subsistence mode. Caries prevalence varied among the sites but there was no correlation with chronological change. The absence of evidence of a decline in dental health over time can be attributed to the relative noncariogenicity of rice and retention of broad-spectrum subsistence strategies. No differences in caries type indicating differences in dental health were found between the sites, apart from the Iron Age site of Muang Sema. There was a higher prevalence of caries in the deciduous dentition than the permanent dentition, likely due to a cariogenic weaning diet and the higher sensitivity of deciduous teeth to decay. The level of caries in the permanent dentition suggests an increased reliance on less cariogenic foods during childhood, including rice. The absence of a temporal decline in dental health of infants and children strengthens the argument that the relationship between caries and agricultural intensification in Southeast Asia was more complex than the general model suggests.

Multivariate analysis of New Guinea and Melanesian skulls: A review

While earlier work in the craniology of New Guinea and Melanesia is legion, more recent investigations which utilize multivariate statistical techniques are few in number. A survey of archaeologically excavated human remains from Papua New Guinea indicates they are scarce and relatively recent. By comparison, museum collections of Melanesian crania are numerous. Particularly noteworthy are the collections found in Europe. Summaries of previous multivariate comparisons of New Guinea and Melanesian cranial data indicate considerable variability within the region. A basic Melanesian pattern, however, is discernible when comparisons are made with the surrounding Pacific region. With even broader comparisions, an Australo-Melanesian-Tasmanian complex can be recognized well differentiated from populations in Asia, Indonesia, and Polynesia, which form a second major complex. While the exact origins of these populations is not clear, multivariate data-analytic approaches help to make clear the nature and extent of cranial variation within New Guinea and Melanesia thus providing an important base for future phylogenetic interpretations. The questions posed in previous research using multivariate statistics and some suggestions for future work are discussed.

Natural Selection and Morphological Variability: The Case of Europe From Neolithic to Modern Times [and Comments and Reply]

Two hypotheses concerning the influence of natural selection intensity on intra- and interpopulational variability of metric characteristics of the human skull ar tested. Using data on 58 series from Europe and its environs dating from Neolithic to modern times, it has been found that with the decline of the decline of the intensity of operation of natural selection (1) intragroup variability increases, (2) intergroup variability decreases, and (3) there is a trend toward shorter, wider, and lower braincase and shorter upper face.