Theses - Biological Anthropology

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Open Access
The role of modularity and integration in shaping primate pelvic girdle evolution
Janin, Katrien Gwennola Rose
This thesis represents, to date, the most comprehensive investigation into the influence of integration (covariation) and modularity (the organisation of integrated units) on the morphological evolution of the primate pelvis. The concepts of integration and modularity are core tenets of evolutionary biology, yet their evolutionary role remains poorly understood. In this thesis, I quantified primate pelvis morphological variation across 4 clades encompassing the main primate locomotory specialisations. Shape was captured in detail, using a surface-based geometric morphometric approach, to test five alternative models of pelvis organisation, calculate integration levels, and reconstruct pelvis evolution. In this thesis, I demonstrate that the primate pelvis is dominantly modulated by developmental pathways, with ilium, ischium, pubis, acetabulum, and sacrum having the capacity to vary and evolve in a relatively independent manner (Chapter 2). This main modular pattern of primates is different to that of carnivores where in the latter group the ischium and pubis covary more closely together. The pubis-ischium parcellation is present in all examined primate phylogenetic groups (Lemuroidea, Ceboidea, Cercopithecoidea, and Hominoidea – humans excluded), suggesting that this parcellation was present in basal primates. Notably, a significant modular signal is also present for the functional hypothesis (locomotion-obstetrics). This suggests that the bony birth canal may vary and evolve relatively independently from the rest of the pelvis shape, alleviating the obstetric dilemma. Overall, this study demonstrates that the modularity pattern of the primate pelvic girdle is not simply limited to its developmental units. Instead, I find modular patterns acting in a complex multi-layered way, with developmental processes synergistically meeting functional needs. Few studies have tried to explicitly clarify the role of integration plays in morphological variability and the evolutionary consequences this entails. In Chapter 3, I calculated the integration levels and tested whether integration may constrain or facilitate evolutionary flexibility and diversity. I found an inverse relationship between integration magnitudes and disparity levels, indicating that the impact of primate pelvis integration is best supported by the hypothesis of constraint across the primate order, its phylogenetic and locomotory groups. My findings highlight the need to consider the impact of integration when modelling shape changes and reconstructing evolutionary pelvic trajectories. In Chapter 4, I examined the role of integration in the morphological divergence of the human pelvis. Human integration levels are marked by a reduction across its developmental and functional pelvic constituents compared to the other sampled primates (Gorilla beringei, Hylobates lar, Pan paniscus and Macaca mulatta). The reduction of inherent human constraint is paired with elevated levels of disparity, indicative of inherent high levels of evolvability present within the human pelvis. Particularly of interest is the low integration signal between the human pubis and ischium, yet the integration levels within these elements are remarkably high. In the case of the pubis, this translates into limited evolutionary possibilities and reduced disparity. Conversely, the high ischium integration acts as a facilitator to morphological disparity, aiding evolutionary responsiveness. The increased evolutionary flexibility of the human ischium played a pivotal role in both bipedal efficiency and increased levels of sexual dimorphism, whereby ischium disparity is also an important aspect in easing parturition. The reduced integration levels between the human developmental and functional pelvis modules provide its pelvic bauplan with increased flexibility to respond to multiple selective pressures, facilitating the complex morphological modifications and divergence of the human pelvis along an evolutionary trajectory that may have otherwise been difficult or even impossible to achieve. This thesis represents a significant advance in the study of pelvic modularity and morphological evolution. Chapters 2 and 3 form a comprehensive baseline for primate pelvis structuration and integration magnitudes, providing an in-depth exploration of hypotheses of modularity and the impact of integration on macroevolutionary patterns. The thesis is also novel in that it investigates developmental and functional integration patterns, and does so across and within species. This provides a multi-layered view of the role of modularity and integration of the primate pelvic girdle.
Open Access
Root Problems in Human Variation
Gellis, Jason; Gellis, Jason [0000-0002-9929-789X]
This dissertation is an investigation of post-canine tooth root morphology in a global sample of modern humans. Tooth roots are variable in number, shape and orientation, and internal canal form and number do not necessarily covary with external morphology. However, this variation is poorly understood in anthropological and biological contexts. This is, in part, due to the inaccessibility of tooth roots for metric and morphological assessment. Early studies relied on x-rays, which are problematic when visualizing root structures, which are often curved or layered one on top of another. Computed tomography (CT) allows for clear visualization of tooth roots, and has revealed a previously unknown, complex combination of external and internal morphologies. Using CT scans from a global sample of humans (n = 945) a novel phenotype system is developed comprised of five elements: Root presence/absence (E1), canal root presence/absence (E2), canal location (E3), external root morphology (E4), and canal morphology and configuration (E5). Together, these five elements capture the external and internal morphology of the tooth root complex and are used to carry out four objectives: (1) to test and describe patterns of variation and divergence between root and canal number in individual teeth and between populations; (2) to develop a predictive model of tooth root morphology based on canal count and configuration; (3) to identify and define the total tooth root phenotypic set of the human sample; (4) to investigate if and how the total phenotypic set can delineate and define geographic and population structure in our sample. Novel statistical approaches are developed and used to ascertain complex patterning. Results indicate that there are clear differences between patterns of root to canal number both within and between teeth of the maxilla and mandible, and that these patterns are different between populations; that root canal number and orientation are powerful predictors of external root morphology; that the combined phenotype elements capture variation within and between populations; and that the combined phenotype elements can accurately identify and delineate population substructures. These findings are discussed in terms of evolutionary and developmental biology and biomechanics, and population structure and diversity.
Open Access
The Agricultural Transition in Upper Nubia: An Analysis of Mandibular Morphology and Oral Health
Brown, Marielle
Research has shown that the biological and morphological effect of the transition to agriculture varied widely by population and geographical region. In Upper Nubia, the shift to full-scale agriculture included transitional phases with varying dependence on pastoralism and farming, alongside continued hunting and gathering. Therefore, Upper Nubia is an ideal region to study the relationship between subsistence strategy, mandibular morphology and oral health. This study analysed the mandibles and dentition from 102 adult individuals from ancient Nubian populations. The sample contained a Late Palaeolithic hunter-gatherer population from Lower Nubia (c. 13,000–9000 BC), as well as samples representing four cultural periods in Upper Nubia (Sudanese Neolithic c. 5000–4000 cal BC, Kerma Ancien c. 2500–2050 BC, Kerma Classique c. 1750–1500 BC and Meroitic c. 350 BC–AD 350). Mandibular osteometrics and cross-sectional geometric properties were calculated from 3D laser scanned models to explore the relationship between diet-induced biomechanical force and variation in mandibular shape and strength between samples. Dental pathology and wear were used to assess diachronic changes in oral health and dietary composition. Dental size was also measured to compare the relationship between mandibular and dental size over time. The intensive agricultural population from the Kerma Classique period had the highest prevalence and severity of dental pathology and wear, which may reflect a highly cariogenic and abrasive diet. Oral health improved in the subsequent Meroitic sample, possibly due to an increase in dietary heterogeneity and/or improved hygienic practices. Overall, mandibles from the Late Palaeolithic hunter-gatherers were longer, wider, and had more upright and larger rami than subsequent agricultural populations. Mandibular size continued to decrease within the subsequent Upper Nubian samples, most notably in the overall length, body height in the molar region and width of the ramus. The gonial angle also became more obtuse over time. Changes in mandibular size were not accompanied by consistent evidence of dental size reduction. In addition, there were significant differences between the Late Palaeolithic and Upper Nubian samples in mandibular biomechanical properties. Most notably, molar Ix and Imax continued to decrease through agricultural intensification in the Upper Nubian samples, suggesting a reduction in the sagittal bending rigidity of the mandible in response to an increasing reliance on softer agricultural food products. The timing of the mandibular morphological changes indicate that the overall size of the mandible began to decrease before strength relative to size. Overall, this study used a novel combination of methodologies to identify major biological changes in the dentition and mandible during the transition to agriculture in Upper Nubia. Importantly, the results demonstrate that changes in masticatory loading magnitude, as a result of dietary shifts, specifically influence mandibular morphology and robusticity in anatomical regions associated with masticatory function, such as the molar region of the mandibular corpus and the ramus. The findings support the masticatory-functional hypothesis and show that dietary changes are an important factor influencing observed mandibular morphological variation between populations. This study contributes to a better understanding of the biological changes that accompanied the agricultural transition in Ancient Nubia.
Open Access
Branching out: A comparative analysis of demographic determinants of mammalian speciation
Van Holstein, Laura
Mammalian speciation is not usually an instantaneous event. It is a protracted process, the course and outcome of which is determined by the interaction between demographic and genetic processes. These demographic processes include the formation of population isolates and the persistence of these isolates. The role and regulators of the demographic determinants of speciation have received some empirical attention, but mostly across birds and squamates. The point of this thesis is to ask what factors regulate the demographic determinants of speciation in mammals, and how these relationships shape macroevolutionary patterns of speciation and species richness. The thesis is divided into two sections that approach the question from different angles. The first is focused on extant mammals and uses subspecies as a proxy for population isolates to ask how ecological factors (1) regulate population isolate formation and (2) mediate the evolutionary trajectory of these isolates. In taking this approach, this section also sheds new light on the debated evolutionary ‘role’ of subspecies in mammals. The second section focuses on a particular subgroup of mammals as a case study: hominins. Hominin speciation rate is calculated across three phylogenies based on different taxonomic approaches. I then test whether climate, time, and interspecific competition explains variation in these rates, and so ask what abiotic or biotic factors determined hominin speciation. Differences between results obtained across more and less inclusive (“lumping” and “splitting”, respectively) phylogenies are then used to link these results to the main question in the thesis. It is suggested that taxa in “split” taxonomies are populations of taxa in “lumped” taxonomies, so that determinants of speciation on “split” taxonomies represent determinants of population isolate formation, and those of speciation on “lumped” taxonomies represent determinants of the rate at which those isolates become detached from the rest of the species. Mammalian population isolate formation provides the raw material for speciation, and the rate at which it occurs is regulated by barriers in the landscape, the level of habitat fragmentation, and climate variability. Speciation is the road less travelled for most mammalian subspecies: and general determinants of the evolutionary trajectory of a mammalian population isolate include ecological substrate and metapopulation niche availability. Across all mammals, terrestrial population isolates become species less often than their non-terrestrial equivalents; and this pattern holds up in hominins. Patterns found across hominins suggest that the probability of a population isolate becoming a novel species can also be determined by whether or not species-level niche space is saturated. An important bridge between population isolate formation and speciation in mammals is the length of population isolate persistence: extended persistence, rather than extending the time it takes to become a full species, increases speciation rate. Again, abiotic factors—particularly climate and possibly habitat fragmentation—are important determinants of this process. Of interest here is the contradicting effects of these abiotic factors: habitat fragmentation promotes population isolate formation across mammals, but it can also curtail how long these isolates persist for. In hominins, a previously unknown role for climate is in mediating the link between intraspecific processes and speciation: the results suggest that longer-term persistence of populations necessary for these to split from the rest of the species tended to occur in more stable climates. Macroevolutionary patterns of mammalian species richness are the cumulative outcome of the balance between population isolate formation and persistence over time: and including demographic determinants of speciation rate in evolutionary models can provide novel insights into why, and how, mammalian species form.
Open Access
Late Quaternary palaeoenvironments and Middle-Late Stone Age habitat preferences in the Nakuru-Naivasha Basin, Kenya: phytolith-based evidence from the site of Prospect Farm
(2020-05-16) Griffith, Peter
The Central Rift Valley of East Africa has proven to be a key region for our understanding the emergence and diversification of our species. Genetic, fossil, archaeological, and palaeoclimatic evidence suggest that mosaic refugia may have existed here during the late Quaternary period. Such putative refugia are posited to have been centered around highland lake basins that could have buffered human populations, plant, and faunal communities from the most severe deteriorations of climate during the last glacial period. On a sub-regional scale, East Africa’s heterogeneous topography and localised expressions of regional climate is hypothesised to have created a ‘push-pull’ system in which repeated fragmentation, isolation, and expansion of populations occurred, allowing diversity to arise. Competing Middle Stone Age (MSA) behavioural-ecological models disagree in respect to their conceptualization of the nature of past human adaptations to xeric savanna, mesic savanna, and forest/wooded habitats, as well as how MSA groups responded to various palaeodemographic pressures. Consequently, these competing models propose contrasting changes in hunter-gatherer mobility and contact/isolation between MSA groups in reaction to the same underlying palaeoenvironmetal and palaeodemographic factors. Local late Quaternary palaeoenvironmental records from archaeological sites in highland areas of East Africa are at present temporally and spatially fragmentary. As such, the relative ecological stability of the Kenyan Central Rift (KCR) and its capacity to have acted as a refugium remain poorly understood, as are the various logistic and adaptive challenges that inhabitants of different ecological zones of East Africa faced. In order to evaluate which behavioural-ecological model(s) best explains patterns in the archaeological record in these settings, this thesis reports the results of phytolith-based vegetation reconstructions and geoarchaeological investigations from renewed excavations at the open-air site of Prospect Farm, Mt. Eburru, Nakuru-Naivasha Basin, Kenya, as part of the In-Africa project (INAP). The Prospect Farm Formation preserves a stratified sequence covering the last glacial period and Holocene, in which four main archaeological phases covering the MSA to Late Stone Age (LSA) transition were previously identified. The site is one of the few which preserve this transition in East Africa, that is associated with major social and technological reorganisation between ~60-20 ka. Consequently, it provides a unique opportunity to establish the environmental context of the MSA-LSA transition in the KCR. Sedimentological, stratigraphic, and elemental analysis (by ICP-OES) of the pyroclastic, colluvial and palaeosol deposits that form the Prospect Farm Formation were conducted to elucidate site formation processes alongside new archaeological investigations of the site. Phytolith analysis (samples [n = 68]) was used to determine temporal and spatial palaeovegetation changes at the site. Phytolith-based palaeovegetation reconstructions were supported by published reference material and a new modern reference collection for the Nakuru-Naivasha Basin. For this new reference set, phytoliths were extracted from little-studied non-grass plants (mainly ligneous and herbaceous dicotyledons [n = 87]) identified as indicator species of different vegetation communities within the study area. Highly diagnostic phytoliths, variation and redundancy in morphology, phytolith production rates across plant families, and dissolution potential were recorded. Multivariate statistical analysis (unconstrained ordination) was used to compare fossil phytolith samples to modern East African soil phytolith assemblages. Phytolith analysis from the six palaeosols studied indicates limited past spatial heterogeneity in plant communities across sampling locations. Results do however demonstrate marked changes in past vegetation composition and human habitat preferences, changing from open xeric C4 grassland to closed canopy Afromontane forest, during the two earliest phases of MSA activity at the site prior to ~50 ka. Environmental variability associated with MSA-LSA ‘transitional’ assemblages was found to be nominal. Habitat reconstructions dispute the long-held view that MSA populations exclusively tracked the ecotonal boundary between montane forest and savannah. This is taken to indicate higher levels of behavioural diversity within MSA groups in this area than had previously been imagined. A new Ar40/Ar39 based chronology and tephrostratigraphy for the site is ongoing; but the environmental variation at Prospect Farm agrees with local lacustrine records and suggests that glacial-interglacial cycles had a significant effect on the basin’s vegetation history and climate. Provisional comparisons with other East African palaeoenvironmental records indicate that the Nakuru-Naivasha Basin remained relatively ecologically stable compared to adjacent lowland areas. While further archaeological analysis is necessary to more fully test competing behavioural-ecological models and the site’s role as a refugium, comparisons of shifts in local ecological conditions to changes in raw material procurement strategies at Prospect Farm indicate that environments with higher arboreal cover tend to be associated with reduced mobility. However, findings also suggest that palaeoclimatic factors are most likely to have played a secondary or mediating role in techno-cultural and mobility changes that occurred during the MSA and across the MSA-LSA transition at Prospect Farm, rather than being a primary driver of these changes.
Open Access
Investigating the role of demography and selection in genome scale patterns of common and rare variant diversity in humans
(2019-11-30) Mörseburg, Alexander
In the last decade, an unprecedented increase in the availability of whole genome sequence (WGS) data has reshaped the field of human evolutionary genomics. However, many earlier sequencing projects like the HapMap and 1000 Genomes panels focussed on a limited set of populations. Therefore, more research has been required to better characterise genetic diversity in understudied regions, such as Island Southeast Asia and Siberia. This thesis contributes to this ongoing effort in the form of three partially related subprojects. Firstly, population structure and local adaptations in Southeast Asia were investigated using novel autosomal 730,000 SNP data from 146 individuals in the context of a larger worldwide panel of 1,825 humans. The Kankanaey Igorot from the highlands of the Philippine Mountain Province were highlighted as the closest living representatives of the source population that may have given rise to the Austronesian expansion. Furthermore, consistent with archaeological, cultural and linguistic evidence of Indian influence in Southeast Asia starting from 2.5 kya South Asian admixture in the region was estimated to date back to the last couple of thousand years. To provide an unbiased high-resolution picture of the patterns of functional and rare variants worldwide high coverage WGS data from 483 individuals (including 379 novel genomes) were analysed. Ingenuity Variant Analysis and the Ensembl Variant Effect Predictor were applied to a subset of these genomes (n = 382) to create a repository of functional and deleterious variants. Evidence for purifying selection in genes involved in pigmentation and immune defence against viruses was detected in African populations. The most differentiated sites across continental groups were integrated with haplotype-based selection tests and annotations from functional databases to pinpoint disease and metabolism-related candidate loci. A subset of the WGS dataset, designed to maximise coverage of diverse ethnic groups (n = 447), was screened for variants occurring exclusively in two individuals in a heterozygous state (f2 variants). It was shown that f2 sharing correlates well with the results of CHROMOPAINTER, a state-of-the-art method to detect recent gene flow, and, allows for the detection of cryptic relatedness among distant populations. This was demonstrated by an example of a previously undetected low-scale African ancestry component in the South American Calchaquíes putatively related to the transatlantic slave trade.
Open Access
Western Gorilla Social Structure and Inter-Group Dynamics
(2019-10-26) Morrison, Robin; Morrison, Robin [0000-0001-9161-4734]
The study of western gorilla social behaviour has primarily focused on family groups, with research on inter-group interactions usually limited to the interactions of a small number of habituated groups or those taking place in a single location. Key reasons for this are the high investment of time and money required to habituate and monitor many groups simultaneously, and the difficulties of making observations on inter-group social interaction in dense tropical rainforest. However, gorilla groups are known to have extensively overlapping home ranges, show affiliative inter-group interactions and often aggregate at resource hotspots. There is also genetic evidence of kin-biased behaviour between dispersed kin. This is all suggestive of a complex society in which inter-group interactions may follow an underlying multi-level social structure where affiliations are influenced by kinship, social exposure, ranging patterns, territoriality or foraging decisions. This thesis investigates the large scale society of western lowland gorillas, using novel technologies and analytical methods to overcome the considerable difficulties in studying large numbers of gorillas simultaneously. I use biases in movement patterns to investigate the cognitive rules used, and decisions made by this intelligent, social species, to navigate the limited space and resources they share with their neighbours. Using observational data from two forest clearings in the Republic of Congo, I quantify community structure by network modularity analysis and hierarchical clustering, demonstrating the presence of kin-based multi-level social structure in western lowland gorilla. The sizes of these gorilla social units follow a hierarchical scaling pattern similar to that observed in other mammalian multi-level societies including humans. The social structure detected at these forest clearings is consistent with a super-spreader structure, suggesting that clearings may act as important transmission hubs for disease, novel ideas, behaviour or culture. This demonstrates that intervention strategies targeting gorillas with home ranges near to forest clearings, particularly solitary males, may be highly effective for limiting the transmission of certain diseases. Modelling the movement patterns of a gorilla population across their ranges using camera trap data demonstrates that gorilla groups appear to actively avoid one another, both through avoidance of other groups at resource hotspots, and avoidance of areas regularly used by other groups. Gorilla groups visit sites less often the closer they are to another group’s home range centre, with groups avoiding larger, more dominant group’s home range centres to a greater extent. This, along with the increased avoidance of visiting a location on the same day as another group when close to their home range centre, is highly suggestive of the presence of territorial defence in western gorillas. The findings in this thesis demonstrate the presence of a kin-based multi-level social structure in western gorillas, with considerable similarities to that present in humans, suggesting that a key component of human social complexity may have evolved far earlier than previously asserted. They suggest that the social brain enhancements observed within the hominin lineage were not necessary to enable human multi-level social structure. I show that western gorillas demonstrate biases in their movement patterns consistent with the presence of some broader elements of territoriality, with regions of priority or even exclusive use, close to their home range centres. My findings strongly emphasise the importance of gorillas as a model system for human social evolution. This is due to both the common underlying multi-level social structure and the considerable similarities in inter-group territorial dynamics. In contrast to previous assumptions that interactions between gorilla groups are primarily random or due to aggressive mate competition, I find that these interactions appear to be based around a complex social structure influenced by kinship, territoriality and dominance.
Open Access
Immune-driven positive and balancing selection in human populations
(2019-07-19) Kaewert, Sarah
This thesis examines the evidence for positive and balancing selection on immune genes in 388 individuals grouped into thirteen geographically diverse populations. The data are high coverage whole genome sequences, many from populations that have been sparsely represented in global genetic diversity studies in the past. Two main analyses were performed for both positive and balancing selection: enrichment tests for each population and class of immune genes, and filtering for top variants or genes driving selection signals. Four different measures of positive selection and three measures of balancing selection were used to scan the whole genome data for evidence of selection. Further filters, including functional importance predictors, were used to filter results for potential driver variants. Positive selection results show significant enrichment for genes associated with bacteria or virus interaction, the innate immune system, and antigen processing and presentation. Results also include variants potentially driving signals of selection. One of these is a missense variant in the Northeast Siberian population in the gene IL27, which is involved in modulation of immune response to infection. Balancing selection enrichment tests show that genes associated with T cell function and antigen processing and presentation are significantly enriched in every population. The HLA region features heavily in these enrichments. One top gene result is GNLY, a gene that produces the antimicrobial protein granulysin, in the West Siberian and Island Southeast Asian populations. Another is PGLYRP4, which is a top gene in seven populations and is involved in recognition and defense against Gram-negative and -positive bacteria. In conclusion, as a general trend there is more enrichment in genes that interact with bacteria and viruses in the positive selection results, and more enrichment in genes involved with antigen processing and presentation and T cell function in the balancing selection results. The combined results show the different immune-driven selection histories of each population, as well as highlight a number of variants and genes that are potential drivers of selection and promising candidates for further study.
Open Access
Bringing to bear: A biosocial examination of the developmental origins of the obstetric dilemma.
(2019-05-18) Decrausaz, Sarah-Louise
Childbirth is biomechanically challenging for humans, as mothers must deliver a relatively large-headed neonate through a narrow birth canal. Previous work has indicated that a narrow birth canal in humans is a result of an anatomical compromise for efficient bipedal locomotion and the ability to give birth to large brained infants. This previous work also suggested that difficult and potentially risk delivery of altricial humans was both evidence of and the solution to the tight relationship between infant size and the maternal birth canal in humans. This is known as the obstetric dilemma (OD). More recent work has complicated the OD and pointed to ecologic context as an influence on pelvic dimensions, suggesting that the mismatch between the maternal birth canal and the size of the human infant may have arisen with the transition to agriculture. This thesis begins with the theme of OD and uses it as a platform to examine the developmental trajectory of the bony pelvis in growing women in the context of childbirth. This project investigates associations between pelvic dimensions, biological and biosocial variables in living girls (n=286) from southern England to clarify the factors affecting the birth canal throughout growth and development. Dual energy x-ray absorptiometry (DXA) can be successfully used to collect pelvic dimensions measurements from healthy, living women. The same pelvic dimensions were collected from magnetic resonance (MRI) and DXA images. DXA measurements all had a higher technical error of measurement than MRI though were within acceptable error limits. Bi-iliac breadth was most closely matched in DXA and MRI measurements. Pelvic measurements collected from DXA scans represent the same biological variation at those collected from MRI scans. Growth curves of pelvic dimensions show that bi-iliac breadth increases in a similar manner to shoulder breadth, whilst the pelvic canal increases in breadth most noticeably between 11 and 17 years of age. Peak growth velocity of the pelvic canal occurs between 11 to 12 years of age, whilst peak bi-iliac and shoulder breadth growth velocity occurs at approximately 8 to 9 years of age. The division in growth patterns between the non-canal and canal components of the pelvis suggest differing patterns in canalization and potential for genetic compared to environmental impact on their morphology. Biological factors that associated with shoulder breadth and bi-iliac breadth were height and thigh circumference, whilst pelvic canal dimensions associated with height and indicators of pubertal development. This suggests that pelvic canal dimensions increase more slowly whilst hip and shoulder breadth increase alongside stature growth in girls. No biosocial factors associated with shoulder breadth or pelvic dimensions, demonstrating stronger associations between biological factors than biosocial factors on pelvic development. These results also underline the unique developmental trajectory of the canal compared to the non-canal components of the pelvis, and suggest that pubertal development indicators (which include localized fat deposits relevant to breastfeeding) align in growth with pelvic canal dimensions. In summary, the findings of this thesis contribute an important basis with which to consider the origins of childbirth difficulty. The results of this project contribute to scholarly work that is redefining the evolutionary origins of childbirth difficulty, proposing more nuanced origins than the original OD hypothesis. The implications of this thesis are that obstetrically relevant pelvic dimensions have a specific growth trajectory that may be impacted by environmental factors in early life and ultimately contribute to childbirth difficulty in adulthood. Results from this work also suggest that the key period of pelvic canal development occurs ahead of puberty whilst also demonstrating that growth priority for the pelvic canal is linked to indicators of pubertal development including localised pockets of adipose tissue. Methodologically this thesis provides a basis for more widespread use of medical imaging in investigating osteological variation. More broadly the results of this work demonstrate that an evolutionary medicine approach that integrates osteological methods and clinical data provides a richer framework to examine the intersections between growth and reproduction in humans.
Open Access
Exploring diachronic changes in activity, diet and health on the prehistoric Baltic coast
(2019-05-18) Rivera, Michael B. C.; Rivera, Michael B. C. [0000-0002-1226-4092]
Beginning around 10,000 years ago, humans gradually shifted away from hunting-and-gathering lifestyles to more sedentary and agricultural lifestyles, which determined a change in their food-sourcing methods. Although the biological effects to changing subsistence patterns are generally well-understood, more recent studies show regional variation in agriculture’s impact on human biology. Archaeology has shown that ancient Baltic populations underwent their own unique transition to agriculture because of their close proximity not only to forests and fertile soils, but also to rivers, lakes and coastlines. This thesis studies the biological implications of coastal living on transitioning communities by examining skeletal variation, dental disease, and indicators of nutritional and general health in Estonian and Latvian individuals dating to the Mesolithic, Neolithic, Bronze Age and Iron Age (9th millennium BC to 1st millennium AD). Biomechanical activity of the upper and lower limbs is shown to be highest in the Baltic Neolithic and Bronze Age relative to earlier hunter-fisher-gatherers and later farming and metallurgic populations. Furthermore, auditory exostoses were identified, perhaps indicative of habitual immersion in cold water for sourcing aquatic foods. These patterns may reflect an increase in manual labor, as well as new suites of food acquisition, with respect to earlier time periods. More recent individuals also exhibit reduced craniofacial and masticatory dimensions, which suggests a decrease in the toughness of food attributable to dietary changes or improvements in food processing. Rates of dental pathologies and indicators of general/nutritional stress show that an unusually high-protein, low-sugar, varied and nutritious diet was consumed by prehistoric Balts in both pre-agricultural and agricultural groups. These various forms of evidence highlight the significance of studying regional variation in agricultural transitions. The reliance on marine and freshwater resources provided Baltic inhabitants with unique types and qualities of food which other transitioning populations elsewhere did not access. This bioarchaeological investigation of the coastal foraging-to-farming transition makes an important contribution to broader scholarship focusing on cultural, technological and biological change at the onset of agriculture.
Open Access
Phenotypic variation and thermoregulation of the human hand
(2018-11-30) Payne, Stephanie; Payne, Stephanie [0000-0002-7173-9262]
The hand has the highest surface area-to-volume ratio of any body part. This property offers the potential for the hand to serve an important function in thermoregulation through radiative heat loss. Theoretically, the capacity for heat loss may be influenced by hand and digit proportions, but the extent to which these proportions influence the hand’s radiative properties remains under-investigated. Although hand morphology is highly constrained by both integration and functional dexterity, phenotypic variation in hand and digit proportions across human populations shows broad ecogeographic patterns. These patterns have been associated with climate adaptation. However, the theory linking climate adaptation to such ecogeographic patterns is based on underlying assumptions relating to thermodynamic principles, which have not been tested in vivo. This study sought to determine the influence of hand and digit proportions on heat loss from the hands directly, the additional anthropometric factors that may affect this relationship, and the impact of variation in hand proportions on dexterity in the cold. The relationship between hand proportions and thermoregulation was tested through both laboratory-based investigation and a field study. The laboratory investigation assessed the relationship between hand proportions and heat loss, the influence of body size and composition on this relationship, and the effect of morphological variation on manual dexterity. Participants (N=114; 18-50 years of age), underwent a 3-minute ice-water hand-immersion. Thermal imaging analysis was used to quantify heat loss. Hand and digit proportions were quantified using 2D and 3D scanning techniques; body size and composition were measured using established anthropometric methods and bio-impedance analysis. After accounting for body size, hand width, digit-to-palm length ratio, and skeletal muscle mass were significant predictors of heat loss from the hand, whilsthand length and fat mass were not. A separate set of participants (N=40) performed a Purdue pegboard dexterity test before and after the immersion test, which demonstrated that digit width alone negatively correlated with dexterity. The field study tested whether phenotypic variation in upper limb proportions could be attributed to cold adaptation or selection for dexterity in living populations exposed to significant energetic stress. Upper limb segment lengths were obtained from participants (N=254; 18-59 years of age), from highland and lowland regions of the Nepalese Himalayas using established anthropometric methods, and relative hand proportions were assessed in relation to severe energetic stress associated with life at high altitude. Relative to height, hand length and hand width were not reduced with altitude stress, whilst ulna length was. This indicates that cold adaptation is not shaping hand proportions in this case, although phenotypic variation in other limb segments may be attributed to cold adaptation or a thrifty phenotype mechanism. The current study provides empirical evidence to support the link between surface area-to-volume ratio, thermodynamic principles and ecogeographical patterns in human hand morphology. However, this research also demonstrates the complexity of the hand’s role in thermoregulation; not only do other factors such as muscularity affect heat loss from the hand, but hand morphology is also highly constrained by integration and dexterity.
Open Access
The Human Faculty for Music: What's special about it?
(2018-11-24) Bispham, John Christopher
Abstract (short version) This thesis presents a model of a narrow faculty for music - qualities that are at once universally present and operational in music across cultures whilst also being specific to our species and to the domain of music. The comparative approach taken focuses on core psychological and physiological capabilities that root and enable appropriate engagement with music rather than on their observable physical correlates. Configurations of musical pulse; musical tone; and musical motivation are described as providing a sustained attentional structure for managing personal experience and interpersonal interaction and as offering a continually renewing phenomenological link between the immediate past, the perceptual present and future expectation. Constituent parts of the narrow faculty for music are considered most fundamentally as a potentiating, quasi-architectural framework in which our most central affective and socio-intentional drives are afforded extended time, stability, and a degree of abstraction, intensity, focus and meaning. The author contends, therefore, that music's defining characteristics, specific functionalities and/or situated efficacies are not demarcated in broadly termed “musical” qualities such as melodic contour or rhythm or in those surprisingly elusive “objective facts” of musical structure. Rather they are solely the attentional/motivational frameworks which root our faculty to make and make sense of music. Our generic capacities for culture and the manifold uses of action, gesture, and sound to express and induce emotion; to regulate affective states; to create or reflect meaning; to signify; to ritualize; coordinate; communicate; interrelate; embody; entrain; and/or intentionalize, none of these is assessed as being intrinsically unique to music performance. Music is, instead, viewed as an ordered expression of human experience, behaviour, interaction, and vitality, all shaped, shared, given significance, and/or transformed in time. The relevance of this model to topical debates on music and evolution is discussed and the author contends that the perspective offered affords significant implications for our understanding of why music is evidently and remarkably effective in certain settings and in the pursuit of certain social, individual, and therapeutic goals.
Open Access
Foraging and Menstruation in the Hadza of Tanzania
(2018-05-19) Fitzpatrick, Katherine
The Hadza, residing near Lake Eyasi in northern Tanzania, represent one of the last remaining hunter-gatherer populations. Inhabiting the same area as our hominin ancestors and exploiting very similar resources, the Hadza maintain a foraging lifestyle characterised by a sexual division of labour. Studies of their foraging and food sharing habits serve as the foundation to numerous hypotheses of human behaviour and evolution. Data from the Hadza have featured heavily in debates on the sexual division of labour. These debates focus predominantly on men’s foraging, including how and why men provision. Women’s provisioning, on the other hand, is seldom explicitly examined and is often presumed to be constrained by reproduction. This thesis contributes to debates on the sexual division of labour by investigating how a woman’s reproductive status affects her foraging behaviours. Observational data on women’s foraging are investigated from 263 person/day follows (1,307 hours total) across 10 camps between 2004 and 2006. These data present the first quantitative documentation of forager women’s eating and sharing outside of camp. Interview data on women’s reproductive timeline are also analysed from in-depth interviews with 58 women from 9 camps in 2015. Spanning from menarche to menopause, these data offer the first quantitative and qualitative documentation of forager women’s menstruation. The results demonstrate that Hadza women eat and share over 800 kilocalories outside of camp per person/day. They regularly give and receive food, including gifts of honey from men. Breastfeeding women are more likely to give gifts and give more gifts than non-breastfeeding women. When they bring nurslings with them outside of camp, they forage less kilocalories per hour. Post-menopausal women eat less relative to what they forage, are less likely to receive gifts, rest less and forage more than pre-menopausal women. Although Hadza women describe their foraging workload as most difficult during late pregnancy, no significant differences in eating, sharing, resting or foraging are observed for pregnant women. Menstrual data from the Hadza reveal that menstruation is not only culturally relevant to the sexual division of labour, but it is also biologically relevant to current understandings of fertility. The majority (60%) of Hadza women report not doing their normal work during menstruation. They also report menstruation-related taboos for berry picking. The thesis presents an in-depth review of women’s menstruation, from the duration of menses to the menstrual cleaning process.
Open Access
Diet Assessment in Tropical African Populations - the implications of detecting biological signals in current diets to the study of past diets
(2018-03-24) Correia, Maria Ana; Correia, Maria Ana [0000-0003-1152-2528]
East Africa is central to many aspects of human evolution and diversification. At the same time, diet is a key aspect of the ecology of any population. Therefore, one is often interested in the diets of past populations. To assess human diet in the past, stable isotope ratio and dental microwear analyses are often perceived as the only semi-quantitative and objective techniques. However, there are still many unknowns on how isotopic and microwear signals change in response to dietary variation, because few controlled studies have been carried out in modern populations. To investigate this issue, this study targeted living humans from African ethnic groups (El Molo, Turkana, Luhya, and Luo, from Kenya, and Baka, from Cameroon) that practise a wide range of traditional subsistence strategies (pastoralism, fishing, and agriculture), with the objective of building a framework in which to consider past diet in an East African context. This study analysed human hair (n = 143), nail (n = 83), and breath (n = 186) for δ$^{13}$C and δ$^{15}$N from the six different communities, and dental moulds (n = 150) from five of those communities (no moulds were collected from the Baka), and related the findings to dietary information. Dental microwear analyses had a low success rate because microwear features were obscured by the biofilm produced by mouth bacteria. Nevertheless, a visual analysis of the results suggested that the El Molo have the hardest and the toughest diet among all the groups studied, possibly through the inclusion of abrasives in the diet during food processing. In turn, the isotopic analyses revealed the ways in which agriculturalists and hunter gatherers differ from pastoralists and fishers in their isotopic values, although the variation in δ$^{13}$C and δ$^{15}$N did not distinguish between pastoralists and fishers. The results emphasise recent changes in the diet of these groups, the importance of local factors in isotope values, and the variable sensitivity of isotopes to dietary practices. In conclusion, although each technique could provide complementary data that would contribute to a more inclusive view of diet, dental microwear analyses are not easily applied to modern human groups, due to the difficulty in acquiring comparative in vivo data, and in distinguishing between patterns caused by food items, or food processing techniques.
Open Access
What’s in a Tooth? Signals of Ecogeography and Phylogeny in the Dentition of Macaques (Cercopithecidae: Macaca)
(2018-02-24) Grunstra, Nicole Dieneke Sybille; Grunstra, Nicole Dieneke Sybille [0000-0002-6708-2245]
The aim of the present work was to investigate the impact of the varying environmental conditions on the taxonomic and phenotypic diversification of a geographically widespread and ecologically successful Old World primate genus, the macaques (Cercopithecidae: Macaca). To this end, the relationship between geography, ecology, phylogeny, and phenotypic variation among macaques was investigated. Constraints to phenotypic variation – and thus evolution – were also analysed in the form of observed amounts of phenotypic variation and patterns of phenotypic integration. A total of 72 standard linear measurements of teeth and associated cranial and mandibular structures were taken for a total sample of 744 specimens from 13 species of macaques. Climate and ecological data were collated from the literature. Univariate and multivariate statistics were employed for the analysis. Patterns of variation, covariation, and allometry were analysed in the dentition, both within and between species. The ecogeographical analysis was carried out by means of two-block partial least squares and a type of multivariate regression, both in a phylogenetic framework. Phylogenetic signal was tested for by means of Blomberg’s K. Macaque teeth differ in their variability. All teeth covary with each other, although correlations are strongest within tooth classes. Size was a strong contributing factor to dental integration, as evinced by lower correlations between teeth once allometric effects were removed. Integration patterns also showed modularity between the anterior and the posterior dentition. Between-species variation in overall craniodental size was associated with temperature, latitude, and body size. Species also varied, albeit to a lesser degree, along an antero-posterior contrast in relative tooth size. Larger anterior were found to be associated with frugivory and tropical ecology, whereas a larger posterior dentition was linked to a more folivorous diet and temperate environments. The latter pattern was largely a function of phylogenetic relatedness. Phylogenetic signal was generally strong in the dentition, although it was substantially greater in the anterior teeth (incisors and canines) than in the posterior teeth (premolars and molars). Macaques show adaptive differentiation in body size in response to temperature along a latitudinal cline, corroborating the presence of the Bergmann effect in macaques. There was no conclusive support for further adaptive differentiation, despite an association between relative tooth size and diet. Allometry appears to channel evolutionary divergence of macaques along a line of least evolutionary resistance, and developmental modularity allows for partly uncoupled evolution of the anterior and posterior dentition. Future research should be aimed at broadening the taxonomic scope to include craniodental variation of the African papionins and cercopithecins in order to put the observed macaque patterns in a broader evolutionary context.
Open Access
Obesity, body fat distribution and other risk factors of non-insulin- dependent diabetes mellitus in different ethnic groups living in East Anglia.
(1995-05-02) Bose, Kaushik Sankar
Open Access
Ontogeny and functional adaptation of trabecular bone in the human foot
(2017-12-01) Saers, Jacobus Petrus Paulus
Trabecular bone forms the internal scaffolding of most bones, and consists of a microscopic lattice-like structure of interconnected bony struts. Experimental work has demonstrated that trabecular bone adapts its structural rigidity and orientation in response to the strains placed upon the skeleton during life, a concept popularly known as “Wolff’s Law” or “bone functional adaptation”. Anthropological work has focused on correlating variation in primate trabecular bone to locomotor and masticatory function, to provide a context for the interpretation of fossil morphology. However, intraspecies variation and its underlying mechanisms are still poorly understood. In this thesis, variation in trabecular bone structure is examined in the human foot in four archaeological populations. The aim is to tease apart the factors underlying variation in human trabecular microstructure to determine whether it may be a suitable proxy for inferring terrestrial mobility in past populations. µCT scanning is used to image the three-dimensional trabecular structure of the talus, calcaneus, and first metatarsal in samples from four archaeological populations. Trabecular structure is quantified in seventeen volumes of interest placed throughout the foot. Trabecular bone is influenced by a variety of factors including body mass, age, diet, temperature, genetics, sex, and mechanical loading. Before trabecular structure can be used to infer habitual behaviour, the effects of these factors need to be understood and ideally statistically accounted for. Therefore, the effects of variation in bone size and shape, body mass, age, and sex on human trabecular structure are examined in four populations. Significant effects of body mass and age are reported, but little sexual dimorphism was found within populations. Taking these results into account, variation in trabecular structure is compared between archaeological populations that were divided into high and low mobility categories. Results demonstrate that the four populations show similar patterns of trabecular variation throughout the foot, with a signal of terrestrial mobility level superimposed upon it. Terrestrial mobility is associated with greater bone volume fraction and thicker, more widely spaced, and less interconnected trabeculae. Ontogeny of trabecular bone in the human calcaneus is investigated in two archaeological populations in the final chapter of the thesis. Results indicate that calcaneal trabecular bone adapts predictably to changes in loading associated with phases of gait maturation and increases in body mass. This opens the possibility of using trabecular structure to serve as a proxy of neuromuscular development in juvenile hominins. This work demonstrates that trabecular bone may serve as a useful proxy of habitual behaviour in hominin fossils and past populations when all contributing factors are carefully considered and ideally statistically controlled for.
Open Access
THE IMPACTS OF CLIMATE AND THE ENVIRONMENT ON HUMAN SKELETAL MORPHOLOGY DURING THE HOLOCENE IN NORTH CHINA A
(2017-06-30) Siew, Yun Ysi; Siew, Yun Ysi [0000-0001-5956-1273]
This dissertation investigates the temporal and regional variation in human skeletal morphology in relation to climate and the environment in Holocene China. Linking skeletal morphology to the changes in climate, subsistence strategy and socio-political development has been well-documented in various geographical areas. Although a general pattern has been observed among different populations, it is evident that local factors have played an equally important role in human morphological variation. China was chosen in this dissertation because its diverse geographical, historical and cultural background provides an ideal setting in which to elucidate human biological responses to a variety different external forces and stimuli. A total sample of 533 adult skeletons, spanning from the mid-Neolithic to the twentieth century, was examined. These skeletons represent the ancient agriculturalists, nomadic pastoralists and agropastoralists inhabiting in contemporary Northeast China and modern humans from South China. This dissertation uses body size and shape, entheseal expression and biomechanical properties of long bones to investigate: 1.) temporal patterns in postcranial dimensions, stature and body mass; 2.) regional differences between the northern and southern Chinese in body size and body/limb proportions; and 3.) variation in skeletal biomechanics and entheses in relation to subsistence strategy. The findings in this dissertation indicated that while the human skeletons studied were morphologically varied throughout Holocene China, they were, to some extent, correlated with climatic and environmental factors. Body size and shape and body/limb proportions corresponded with variation in temperature. Additionally, stature, body mass and entheseal expression were correlated with socio-political and cultural development. Nevertheless, entheseal expression unexpectedly did not show a straightforward relationship with subsistence strategy, in which is inconsistent with the findings of previous studies. Although the comparisons of biomechanical properties were not unequivocal, they suggest differences in mobility and mechanical loading between different populations and subsistence strategies. On the whole, the results suggested that variation in skeletal morphology of the Holocene Chinese follows the universal patterns on the one hand, while on the other, they were influenced by local environmental and behavioural factors.
Open Access
Biological evolution and population change in the European Upper Palaeolithic
(1995) Schumann, Betsy Ann
The European Upper Palaeolithic, from 45,000 to 10,000 BP, marks the first appearance of anatomically modern Homo sapiens in Europe. The skeletal morphology of these earliest modern humans has played a large role in the debate over modern human origins. While it is important to investigate the various origins theories and examine available fossil data in conjunction with modern, present day skeletal material, studies of late Pleistocene evolutionary change remain inconclusive. The work which has been conducted on Upper Palaeolithic cranial change has proposed that there are regional patterns and differences in cranial robusticity which has been interpreted as genetic admixture between Neanderthals and modern humans and chronological patterns which indicate systematic gracilization in cranial and dental morphology. Furthermore, it has been suggested that the earliest modern humans from the late Pleistocene were morphologically different from recent modern human populations. Therefore, it is not only necessary to examine the changes that occurred which lead to our modernity and the archaic-modern relationship but it appears equally paramount to examine the continual evolutionary changes occurring after humans became modern, during the Late Palaeolithic. This study provides data from sixty European Upper Palaeolithic fossil hominids drawn from a 35,000 year period and from all parts of Europe. Metric and non-metric data were collected on cranial and dental material. The results are presented on the range of morphological variation in relation to a series of modern human controls. Patterns in cranial and dental variation are then tested within three frameworks: firstly, chronological trends in the Upper Palaeolithic; secondly, geographical (regional) distribution across Europe; and thirdly, in relation to the archaeological and behavioural record of the Upper Palaeolithic. The results are discussed in the context of the affinities of the first anatomically modern Europeans and the extent to which change or continuity can be observed over this period. The analysis for morphological change through time indicated that while there are several cranial featurcis which show a marked reduction throughout the Upper Palaeolithic and others which display a less severe 'trend' towards gracilization, these changes are attributable to specific, robust morphological characteristics of the Central European hominid material, rather than a general process of 'gracilization'. These results have implications for whether the European Upper Palaeolithic is characterised by indigenous population changes or subject to external influences, as well as the relationship between biological evolution and the archaeological record.
Open Access
Capuchin monkey and the Caatinga dry forest : a hard life in a harsh habitat.
(2005-02-15) Moura, Antonio Christian de Andrade.
This thesis explores the seemingly simple problem of how a rainforest-dwelling primate, Cebus apella libidinosus, manages to survive in the Caatinga dry forest of north-eastern Brazil, a harsh habitat that poses a series of extreme ecological challenges for survival. Albeit a simple question, it unfolds into more complex questions regarding how ecological pressures might drive brain evolution and intelligence in primates. Although there is no "best" hypothesis to explain the evolutionary brain enlargement in higher primates, fine-grained analyses of ecology, such as those presented here provide insights into how different species deal with ecological problems that might require cognitive solutions. Capuchin monkeys are an ideal model for this inquiry. They occupy diverse habitats, and they have proven to be a cognitive puzzle. They are the only monkey to approach great apes in their ability to use tools, but apparently lack the prerequisite mental capability to understand cause and effect. The Caatinga dry forest poses a series of ecological challenges for mammals in general and primates in particular, and these are detailed in this thesis. This is the first general study of mammalian abundance and distribution in Caatinga habitats, with special reference to Cebus. I present several innovative methods for assessing plant and invertebrate biodiversity, as regards foods for the Cebus. The study population of capuchin monkeys faced more frequent and longer periods of food scarcity than does any other known capuchin population. However, the Cebus in the Caatinga circumvent the ecological constraints of low plant food availability through their proficient foraging style (destructive foraging) and through their cognitive abilities, reflected in this population's extensive and intelligent use of technology. I suggest that Old World monkeys and capuchin monkeys have undergone differential selective pressures, with 'Machiavellian intelligence' being a more prominent aspect in the brain evolution of baboons and macaques, while extractive foraging was a more important selective pressure for capuchin monkeys. The evolutionary brain enlargement observed in hominids is suggested to be a legacy of extractive foraging and that capuchin monkeys are excellent models for understanding the factors leading to brain enlargement. This thesis is concluded as an endeavour into understanding the selective forces and concatenation of events that culminated with the evolutionary brain enlargement seen in the hominins.