Palaeoenvironments and hominin evolutionary dynamics in southeast Asia.

Secure environmental contexts are crucial for hominin interpretation and comparison. The discovery of a Denisovan individual and associated fauna at Tam Ngu Hao 2 (Cobra) Cave, Laos, dating back to 164-131 ka, allows for environmental comparisons between this (sub)tropical site and the Palearctic Denisovan sites of Denisova Cave (Russia) and Baishiya Karst Cave (China). Denisovans from northern latitudes foraged in a mix of forested and open landscapes, including tundra and steppe. Using stable isotope values from the Cobra Cave assemblage, we demonstrate that, despite the presence of nearby canopy forests, the Denisovan individual from Cobra Cave primarily consumed plants and/or animals from open forests and savannah. Using faunal evidence and proxy indicators of climates, results herein highlight a local expansion of rainforest at ~ 130 ka, raising questions about how Denisovans responded to this local climate change. Comparing the diet and habitat of the archaic hominin from Cobra Cave with those of early Homo sapiens from Tam Pà Ling Cave (46-43 ka), Laos, it appears that only our species was able to exploit rainforest resources.

Early presence of Homo sapiens in Southeast Asia by 86-68 kyr at Tam Pà Ling, Northern Laos.

The timing of the first arrival of Homo sapiens in East Asia from Africa and the degree to which they interbred with or replaced local archaic populations is controversial. Previous discoveries from Tam Pà Ling cave (Laos) identified H. sapiens in Southeast Asia by at least 46 kyr. We report on a recently discovered frontal bone (TPL 6) and tibial fragment (TPL 7) found in the deepest layers of TPL. Bayesian modeling of luminescence dating of sediments and U-series and combined U-series-ESR dating of mammalian teeth reveals a depositional sequence spanning ~86 kyr. TPL 6 confirms the presence of H. sapiens by 70 ± 3 kyr, and TPL 7 extends this range to 77 ± 9 kyr, supporting an early dispersal of H. sapiens into Southeast Asia. Geometric morphometric analyses of TPL 6 suggest descent from a gracile immigrant population rather than evolution from or admixture with local archaic populations.

A Middle Pleistocene Denisovan molar from the Annamite Chain of northern Laos.

The Pleistocene presence of the genus Homo in continental Southeast Asia is primarily evidenced by a sparse stone tool record and rare human remains. Here we report a Middle Pleistocene hominin specimen from Laos, with the discovery of a molar from the Tam Ngu Hao 2 (Cobra Cave) limestone cave in the Annamite Mountains. The age of the fossil-bearing breccia ranges between 164-131 kyr, based on the Bayesian modelling of luminescence dating of the sedimentary matrix from which it was recovered, U-series dating of an overlying flowstone, and U-series-ESR dating of associated faunal teeth. Analyses of the internal structure of the molar in tandem with palaeoproteomic analyses of the enamel indicate that the tooth derives from a young, likely female, Homo individual. The close morphological affinities with the Xiahe specimen from China indicate that they belong to the same taxon and that Tam Ngu Hao 2 most likely represents a Denisovan.

Trophic ecology of a Late Pleistocene early modern human from tropical Southeast Asia inferred from zinc isotopes.

Tam Pà Ling, a cave site in northeastern Laos, has yielded the earliest skeletal evidence of Homo sapiens in mainland Southeast Asia. The reliance of Pleistocene humans in rainforest settings on plant or animal resources is still largely unstudied, mainly due to poor collagen preservation in fossils from tropical environments precluding stable nitrogen isotope analysis, the classical trophic level proxy. However, isotopic ratios of zinc (Zn) in bioapatite constitute a promising proxy to infer trophic and dietary information from fossil vertebrates, even under adverse tropical taphonomic conditions. Here, we analyzed the zinc isotope composition (66Zn/64Zn expressed as δ66Zn value) in the enamel of two teeth of the Late Pleistocene (63-46 ka) H. sapiens individual (TPL1) from Tam Pà Ling, as well as 76 mammal teeth from the same site and the nearby Nam Lot cave. The human individual exhibits relatively low enamel δ66Zn values (+0.24‰) consistent with an omnivorous diet, suggesting a dietary reliance on both plant and animal matter. These findings offer direct evidence of the broad utilization of resources from tropical rainforests by one of the earliest known anatomically modern humans in Southeast Asia.

A multi-proxy approach to exploring Homo sapiens' arrival, environments and adaptations in Southeast Asia.

The capability of Pleistocene hominins to successfully adapt to different types of tropical forested environments has long been debated. In order to investigate environmental changes in Southeast Asia during a critical period for the turnover of hominin species, we analysed palaeoenvironmental proxies from five late Middle to Late Pleistocene faunas. Human teeth discoveries have been reported at Duoi U'Oi, Vietnam (70-60 ka) and Nam Lot, Laos (86-72 ka). However, the use of palaeoproteomics allowed us to discard the latter, and, to date, no human remains older than ~ 70 ka are documented in the area. Our findings indicate that tropical rainforests were highly sensitive to climatic changes over that period, with significant fluctuations of the canopy forests. Locally, large-bodied faunas were resilient to these fluctuations until the cooling period of the Marine Isotope Stage 4 (MIS 4; 74-59 ka) that transformed the overall biotope. Then, under strong selective pressures, populations with new phenotypic characteristics emerged while some other species disappeared. We argue that this climate-driven shift offered new foraging opportunities for hominins in a novel rainforest environment and was most likely a key factor in the settlement and dispersal of our species during MIS 4 in SE Asia.

Use of Virtual Reality to Educate Undergraduate Medical Students on Cardiac Peripheral and Collateral Circulation.

Many medical schools are looking to utilize virtual reality (VR); however, due to its novelty, we know little about how VR can be effectively used in medical education. This study evaluates a case-centered VR task that supported students with learning peripheral and collateral circulation, anatomical features that are not easily observed in cadavers. Data sources included a quiz, survey, and focus group. Based on quantitative and qualitative analyses, we support the claim that this activity was an effective use of VR and identify features that made it effective, which can guide other educators who are interested in developing VR activities.

Pelvic Floor Dysfunction After Hysterectomy: Moving the Investigation Forward.

The role of hysterectomy in the development of pelvic floor dysfunction (PFD) remains widely disputed. The controversy is fueled by two key factors. The first is conflicting association studies that make it difficult to establish whether a link truly exists. Although many retrospective studies report a correlation between hysterectomy and increased risk of stress urinary incontinence (SUI) or pelvic organ prolapse (POP), prospective studies often fail to replicate these results, leading some to conclude that no association exists. However, most prospective studies do not follow up for a sufficient length of time to account for the long latency of PFD and cannot unilaterally prove the absence of an association. The second source of controversy is the absence of a plausible mechanism to explain how hysterectomy could predispose patients to PFD. In this paper, we investigate autonomic innervation and smooth muscle in the three layers of pelvic floor support and propose a mechanism through which autonomic damage from hysterectomy could predispose patients to PFD. We then identify key research areas needed to evaluate this theory. This report aims to inspire a discussion on how to further the collective understanding of the relationship between hysterectomy and PFD. Clarifying the nature of this connection could have enormous consequences in redefining the risks and benefits of hysterectomy.

Zinc isotopes in Late Pleistocene fossil teeth from a Southeast Asian cave setting preserve paleodietary information.

Stable carbon and nitrogen isotope ratios of collagen from bone and dentin have frequently been used for dietary reconstruction, but this method is limited by protein preservation. Isotopes of the trace element zinc (Zn) in bioapatite constitute a promising proxy to infer dietary information from extant and extinct vertebrates. The 66Zn/64Zn ratio (expressed as δ66Zn value) shows an enrichment of the heavy isotope in mammals along each trophic step. However, preservation of diet-related δ66Zn values in fossil teeth has not been assessed yet. Here, we analyzed enamel of fossil teeth from the Late Pleistocene (38.4-13.5 ka) mammalian assemblage of the Tam Hay Marklot (THM) cave in northeastern Laos, to reconstruct the food web and assess the preservation of original δ66Zn values. Distinct enamel δ66Zn values of the fossil taxa (δ66Zncarnivore < δ66Znomnivore < δ66Znherbivore) according to their expected feeding habits were observed, with a trophic carnivore-herbivore spacing of +0.60‰ and omnivores having intermediate values. Zn and trace element concentration profiles similar to those of modern teeth also indicate minimal impact of diagenesis on the enamel. While further work is needed to explore preservation for settings with different taphonomic conditions, the diet-related δ66Zn values in fossil enamel from THM cave suggest an excellent long-term preservation potential, even under tropical conditions that are well known to be adverse for collagen preservation. Zinc isotopes could thus provide a new tool to assess the diet of fossil hominins and associated fauna, as well as trophic relationships in past food webs.

The prehistoric peopling of Southeast Asia.

The human occupation history of Southeast Asia (SEA) remains heavily debated. Current evidence suggests that SEA was occupied by Hòabìnhian hunter-gatherers until ~4000 years ago, when farming economies developed and expanded, restricting foraging groups to remote habitats. Some argue that agricultural development was indigenous; others favor the "two-layer" hypothesis that posits a southward expansion of farmers giving rise to present-day Southeast Asian genetic diversity. By sequencing 26 ancient human genomes (25 from SEA, 1 Japanese Jomon), we show that neither interpretation fits the complexity of Southeast Asian history: Both Hòabìnhian hunter-gatherers and East Asian farmers contributed to current Southeast Asian diversity, with further migrations affecting island SEA and Vietnam. Our results help resolve one of the long-standing controversies in Southeast Asian prehistory.

Dental phenotypic shape variation supports a multiple dispersal model for anatomically modern humans in Southeast Asia.

The population history of anatomically modern humans (AMH) in Southeast Asia (SEA) is a highly debated topic. The impact of sea level variations related to the Last Glacial Maximum (LGM) and the Neolithic diffusion on past population dispersals are two key issues. We have investigated competing AMH dispersal hypotheses in SEA through the analysis of dental phenotype shape variation on the basis of very large archaeological samples employing two complementary approaches. We first explored the structure of between- and within-group shape variation of permanent human molar crowns. Second, we undertook a direct test of competing hypotheses through a modeling approach. Our results identify a significant LGM-mediated AMH expansion and a strong biological impact of the spread of Neolithic farmers into SEA during the Holocene. The present work thus favors a "multiple AMH dispersal" hypothesis for the population history of SEA, reconciling phenotypic and recent genomic data.

Incisor ablation among the late upper paleolithic people of Tam Hang (Northern Laos): Social identity, mortuary practice, and oral health.

OBJECTIVES: A detailed assessment of intentional incisor ablation among the Late Upper Paleolithic people of Tam Hang (northern Laos) was undertaken to understand how this cultural practice, in addition to age and sex, influenced an individual's inclusion in the mortuary context. The covariation of ablation status with occlusal variation and anterior dental pathology was addressed to study the implications of this cultural practice on oral health. MATERIALS AND METHODS: Sex, age, caries, antemortem tooth loss, and occlusal variation were assessed through standard osteological methods for 12 individuals. An observational protocol to identify intentional ablation was developed specifically for this sample. RESULTS: Four ablation states were identified that range from no ablation to the removal of two, three, or four lateral (I2) incisors. The timing of ablation was attributed to ritual extractions during early adolescence. Adult age-at-death was the strongest indicator of inclusion in the main burial context and a child burial was isolated from those of adults. Ablation status does not strongly influence inclusion in the mortuary context. Individuals lacking ablation tended to have a higher incidence of anterior caries, pathological tooth loss, incisor crowding, and canine rotation. CONCLUSIONS: This study identifies the oldest case of intentional incisor ablation in Late Pleistocene Mainland Southeast Asia. We conclude that ablation does not always "compromise" the dentition; instead, it may have unintentional oral health benefits in some contexts. Am J Phys Anthropol 160:519-528, 2016. © 2016 Wiley Periodicals, Inc.

Early modern humans and morphological variation in Southeast Asia: fossil evidence from Tam Pa Ling, Laos.

Little is known about the timing of modern human emergence and occupation in Eastern Eurasia. However a rapid migration out of Africa into Southeast Asia by at least 60 ka is supported by archaeological, paleogenetic and paleoanthropological data. Recent discoveries in Laos, a modern human cranium (TPL1) from Tam Pa Ling's cave, provided the first evidence for the presence of early modern humans in mainland Southeast Asia by 63-46 ka. In the current study, a complete human mandible representing a second individual, TPL 2, is described using discrete traits and geometric morphometrics with an emphasis on determining its population affinity. The TPL2 mandible has a chin and other discrete traits consistent with early modern humans, but it retains a robust lateral corpus and internal corporal morphology typical of archaic humans across the Old World. The mosaic morphology of TPL2 and the fully modern human morphology of TPL1 suggest that a large range of morphological variation was present in early modern human populations residing in the eastern Eurasia by MIS 3.

Anatomically modern human in Southeast Asia (Laos) by 46 ka.

Uncertainties surround the timing of modern human emergence and occupation in East and Southeast Asia. Although genetic and archeological data indicate a rapid migration out of Africa and into Southeast Asia by at least 60 ka, mainland Southeast Asia is notable for its absence of fossil evidence for early modern human occupation. Here we report on a modern human cranium from Tam Pa Ling, Laos, which was recovered from a secure stratigraphic context. Radiocarbon and luminescence dating of the surrounding sediments provide a minimum age of 51-46 ka, and direct U-dating of the bone indicates a maximum age of ~63 ka. The cranium has a derived modern human morphology in features of the frontal, occipital, maxillae, and dentition. It is also differentiated from western Eurasian archaic humans in aspects of its temporal, occipital, and dental morphology. In the context of an increasingly documented archaic-modern morphological mosaic among the earliest modern humans in western Eurasia, Tam Pa Ling establishes a definitively modern population in Southeast Asia at ~50 ka cal BP. As such, it provides the earliest skeletal evidence for fully modern humans in mainland Southeast Asia.

Estimating the distribution of probable age-at-death from dental remains of immature human fossils.

In two historic longitudinal growth studies, Moorrees et al. (Am J Phys Anthropol 21 (1963) 99-108; J Dent Res 42 (1963) 1490-1502) presented the "mean attainment age" for stages of tooth development for 10 permanent tooth types and three deciduous tooth types. These findings were presented graphically to assess the rate of tooth formation in living children and to age immature skeletal remains. Despite being widely cited, these graphical data are difficult to implement because there are no accompanying numerical values for the parameters underlying the growth data. This analysis generates numerical parameters from the data reported by Moorrees et al. by digitizing 358 points from these tooth formation graphs using DataThief III, version 1.5. Following the original methods, the digitized points for each age transition were conception-corrected and converted to the logarithmic scale to determine a median attainment age for each dental formation stage. These values are subsequently used to estimate age-at-death distributions for immature individuals using a single tooth or multiple teeth, including estimates for 41 immature early modern humans and 25 immature Neandertals. Within-tooth variance is calculated for each age estimate based on a single tooth, and a between-tooth component of variance is calculated for age estimates based on two or more teeth to account for the increase in precision that comes from using additional teeth. Finally, we calculate the relative probability of observing a particular dental formation sequence given known-age reference information and demonstrate its value in estimating age for immature fossil specimens.

Regional variation in the postcranial robusticity of late Upper Paleolithic humans.

Early modern humans from the European Upper Paleolithic (UP) demonstrate trends in postcranial biomechanical features that coincide with the last glacial maximum (LGM). These features have been interpreted as evidence that ecological changes of the LGM played a critical role in cultural and biological adaptation in European UP populations. In areas outside of Europe, similar environmental changes occurred with the LGM. This analysis introduces postcranial material from the Late Upper Paleolithic (LUP) of North Africa and Southeast Asia and tests two related hypotheses: 1) LUP samples across the Old World had similar patterns of postcranial robusticity and 2) relative to an available Early Upper Paleolithic (EUP) sample, regional LUP samples demonstrate similar trends in robusticity that may be attributable to climatic effects of the LGM. Cross-sectional geometric data of the humeri and femora were obtained for 26 EUP and 100 LUP humans from Europe, Africa, and Asia. Despite regional differences, LUP samples are similar relative to the EUP sample. In the humerus, bilateral asymmetry decreases in all LUP samples relative to the EUP sample. In the femur, LUP samples demonstrate increasingly circular femoral midshaft sections, reflecting reduced anteroposterior bending strength relative to the EUP sample. These patterns suggest changes in subsistence behavior and mobility after the LGM across the Old World that are most consistent with reduced mobility and broad-spectrum resource exploitation.

Morphological variation and airflow dynamics in the human nose.

Airflow dynamics are recognized as being important to the functioning of the human nose in conditioning and filtering inspired air, yet these dynamics are poorly understood. Despite considerable research on airflow dynamics by otolaryngologists, respiratory physiologists, and toxicologists, major disagreements remain about the nature of airflow in the human nose. Specifically, there is little consensus about the character of nasal airflow regimes (laminar or turbulent) and about the major pathways of airflow through the internal chamber. Additionally, a number of features in the human nose have been argued to enhance airflow turbulence, thus increasing the exposure of moving air to the nasal mucosa and facilitating heat and moisture exchange in cold and/or dry climates. These features include: an inferior orientation of the nares; a nasal sill that is high relative to the floor of the internal nasal chamber; a nasal valve that is small in cross-sectional area relative to that of the internal chamber; and large, projecting conchae. The claim that these features affect airflow dynamics has never been tested. To clarify the nature of human nasal airflow and to test these claims of functional significance to nasal variation, we studied airflow across physiological flow rates using water and dye flowing through anatomically accurate acrylic models of human nasal air passageways (with adjustment of water flow rates to maintain dynamic similarity). The models were derived from direct casting of the nasal passageways of 10 Caucasian ("leptorrhine") cadavers (six male, four female). Measures of naris angle, nasal sill height, nasal valve area relative to internal chamber cross-sectional area, and relative projection of the inferior and middle turbinates were taken directly on the resulting casts. The relationships between aspects of nasal morphology and turbulent air flow were evaluated by examining the flow regimes (laminar, semiturbulent, or turbulent) at varying flow rates, with the expectation that the greater the development of the proposed turbulence-enhancing features the slower the flow rate at which flow would shift from one regime to another. Flow characteristics (both flow regimes and principal pathways) were highly variable within our sample. The relative projection of the inferior turbinate was the only variable that significantly affected the flow rate at which flow became turbulent. However, more projecting turbinates appear to laminate flow rather than to induce turbulence. Nostril orientation was moderately correlated with flow dynamics (with more inferiorly directed nares producing turbulence at slower flow rates), but this correlation was not statistically significant. Relative nasal valve area and nasal sill height were unrelated to turbulence in our models.

Late pleistocene human femoral diaphyseal curvature.

Anterior femoral curvature is a consistent characteristic of Pleistocene and recent humans, although variation exists in the degree of curvature among individuals and across populations. In particular, one group, the Neandertals, has been characterized for a century as having marked femoral curvature. To evaluate the degree of anterior femoral curvature in both Neandertals and other Late Pleistocene humans, their curvature subtenses and proximodistal positions were evaluated in the context of recent human variation. Recent human comparisons show little relationship between subtense (absolute curvature) and femoral length, suggesting that an index that incorporates subtense relative to the length of the femur is inappropriate for between-group assessments. Neandertals were statistically indistinguishable from Middle or earlier Upper Paleolithic modern humans in the degree of absolute curvature, all of whom had greater curvature on average than all later humans. Additionally, Neandertals and Qafzeh-Skhul early modern humans had a more distal point of maximum curvature than any other group. Curvature was not strongly correlated with functional considerations including body mass estimates, surrogate variables for body size, proximal femoral articular orientation, or knee anteroposterior dimensions. The functional role of femoral anterior curvature is unknown; however, the general decrease in curvature subtense closely parallels the between-group changes in inferred levels of mobility from femoral diaphyseal robusticity and shape, suggesting that femoral curvature may reflect mobility levels and patterns among Late Pleistocene and recent humans.