Contextualising primate origins - an ecomorphological framework

Ecomorphology - the characterisation of the adaptive relationship between an organism's morphology and its ecological role - has long been central to theories of the origin and early evolution of the primate order. This is exemplified by two of the most influential theories of primate origins: Matt Cartmill's Visual Predation Hypothesis, and Bob Sussman's Angiosperm Co-Evolution Hypothesis. However, the study of primate origins is constrained by the absence of data directly documenting the events under investigation, and has to rely instead on a fragmentary fossil record and the methodological assumptions inherent in phylogenetic comparative analyses of extant species. These constraints introduce particular challenges for inferring the ecomorphology of primate origins, as morphology and environmental context must first be inferred before the relationship between the two can be considered. Fossils can be integrated in comparative analyses and observations of extant model species and laboratory experiments of form-function relationships are critical for the functional interpretation of the morphology of extinct species. Recent developments have led to important advancements, including phylogenetic comparative methods based on more realistic models of evolution, and improved methods for the inference of clade divergence times, as well as an improved fossil record. This contribution will review current perspectives on the origin and early evolution of primates, paying particular attention to their phylogenetic (including cladistic relationships and character evolution) and environmental (including chronology, geography, and physical environments) contextualisation, before attempting an up-to-date ecomorphological synthesis of primate origins

Brain enlargement and dental reduction were not linked in hominin evolution

The large brain and small postcanine teeth of modern humans are among our most distinctive features, and trends in their evolution are well studied within the hominin clade. Classic accounts hypothesize that larger brains and smaller teeth coevolved because behavioral changes associated with increased brain size allowed a subsequent dental reduction. However, recent studies have found mismatches between trends in brain enlargement and posterior tooth size reduction in some hominin species. We use a multiple-variance Brownian motion approach in association with evolutionary simulations to measure the tempo and mode of the evolution of endocranial and dental size and shape within the hominin clade. We show that hominin postcanine teeth have evolved at a relatively consistent neutral rate, whereas brain size evolved at comparatively more heterogeneous rates that cannot be explained by a neutral model, with rapid pulses in the branches leading to later Homo species. Brain reorganization shows evidence of elevated rates only much later in hominin evolution, suggesting that fast-evolving traits such as the acquisition of a globular shape may be the result of direct or indirect selection for functional or structural traits typical of modern humans

Exceptional Evolutionary Expansion of Prefrontal Cortex in Great Apes and Humans

One of the enduring questions that has driven neuroscientific enquiry in the last century has been the nature of differences in the prefrontal cortex of humans versus other animals [1]. The prefrontal cortex has drawn particular interest due to its role in a range of evolutionarily specialized cognitive capacities such as language [2], imagination [3], and complex decision making [4]. Both cytoarchitectonic [5] and comparative neuroimaging [6] studies have converged on the conclusion that the proportion of prefrontal cortex in the human brain is greatly increased relative to that of other primates. However, considering the tremendous overall expansion of the neocortex in human evolution, it has proven difficult to ascertain whether this extent of prefrontal enlargement follows general allometric growth patterns, or whether it is exceptional [1]. Species’ adherence to a common allometric relationship suggests conservation through phenotypic integration, while species’ deviations point toward the occurrence of shifts in genetic and/or developmental mechanisms. Here we investigate prefrontal cortex scaling across anthropoid primates and find that great ape and human prefrontal cortex expansion are non-allometrically derived features of cortical organization. This result aligns with evidence for a developmental heterochronic shift in human prefrontal growth [7, 8], suggesting an association between neurodevelopmental changes and cortical organization on a macroevolutionary scale. The evolutionary origin of non-allometric prefrontal enlargement is estimated to lie at the root of great apes (∼19–15 mya), indicating that selection for changes in executive cognitive functions characterized both great ape and human cortical organization

The evolution of mammalian brain size

Relative brain size has long been considered a reflection of cognitive capacities and has played a fundamental role in developing core theories in the life sciences. Yet, the notion that relative brain size validly represents selection on brain size relies on the untested assumptions that brain-body allometry is restrained to a stable scaling relationship across species and that any deviation from this slope is due to selection on brain size. Using the largest fossil and extant dataset yet assembled, we find that shifts in allometric slope underpin major transitions in mammalian evolution and are often primarily characterized by marked changes in body size. Our results reveal that the largest-brained mammals achieved large relative brain sizes by highly divergent paths. These findings prompt a reevaluation of the traditional paradigm of relative brain size and open new opportunities to improve our understanding of the genetic and developmental mechanisms that influence brain size

Розрахунок та проектування окремого фундаменту будівлі на природній ґрунтовій основі. Методичні рекомендації до виконання практичних завдань та курсового проекту з дисципліни «Механіка ґрунтів, основи і фундаменти» сту- дентами напрямів підготовки 6.060101 Будівництво та 6.050301 Гірництво

Подано методичні рекомендації до виконання практичних завдань та кур- сового проекту з дисципліни «Механіка ґрунтів, основи і фундаменти» для сту- дентів напрямів підготовки 6.060101 Будівництво та 6.050301 Гірництво. Розглянуто порядок проектування фундаменту будівлі мілкого закладан- ня на природній ґрунтовій основі. Методичні рекомендації передбачають виконання курсового проекту «Розрахунок та проектування окремого фундаменту будівлі на природній ґрун- товій основі» як із викладачем, так і під час самостійної роботи. Можна використовувати також у підготовці курсового та дипломного про- ектування

Shared Pattern of Endocranial Shape Asymmetries among Great Apes, Anatomically Modern Humans, and Fossil Hominins

Anatomical asymmetries of the human brain are a topic of major interest because of their link with handedness and cognitive functions. Their emergence and occurrence have been extensively explored in human fossil records to document the evolution of brain capacities and behaviour. We quantified for the first time antero-posterior endocranial shape asymmetries in large samples of great apes, modern humans and fossil hominins through analysis of “virtual” 3D models of skull and endocranial cavity and we statistically test for departures from symmetry. Once based on continuous variables, we show that the analysis of these brain asymmetries gives original results that build upon previous analysis based on discrete traits. In particular, it emerges that the degree of petalial asymmetries differs between great apes and hominins without modification of their pattern. We indeed demonstrate the presence of shape asymmetries in great apes, with a pattern similar to modern humans but with a lower variation and a lower degree of fluctuating asymmetry. More importantly, variations in the position of the frontal and occipital poles on the right and left hemispheres would be expected to show some degree of antisymmetry when population distribution is considered, but the observed pattern of variation among the samples is related to fluctuating asymmetry for most of the components of the petalias. Moreover, the presence of a common pattern of significant directional asymmetry for two components of the petalias in hominids implicates that the observed traits were probably inherited from the last common ancestor of extant African great apes and Homo sapiens

Worldwide variation in hip fracture incidence weakly aligns with genetic divergence between populations.

UnlabelledThis study investigates the influence of genetic differentiation in determining worldwide heterogeneity in osteoporosis-related hip fracture rates. The results indicate that global variation in fracture incidence exceeds that expected on the basis of random genetic variance.IntroductionWorldwide, the incidence of osteoporotic hip fractures varies considerably. This variability is believed to relate mainly to non-genetic factors. It is conceivable, however, that genetic susceptibility indeed differs across populations. Here, we present the first quantitative assessment of the effects of genetic differentiation on global variability in hip fracture rates.MethodsWe investigate the observed variance in publically reported age-standardized rates of hip fracture among 28 populations from around the world relative to the expected variance given the phylogenetic relatedness of these populations. The extent to which these variances are similar constitutes a "phylogenetic signal," which was measured using the K statistic. Population genetic divergence was calculated using a robust array of genome-wide single nucleotide polymorphisms.ResultsWhile phylogenetic signal is maximized when K > 1, a K value of only 0.103 was detected in the combined-sex fracture rate pattern across the 28 populations, indicating that fracture rates vary more than expected based on phylogenetic relationships. When fracture rates for the sexes were analyzed separately, the degree of phylogenetic signal was also found to be small (females: K = 0.102; males: K = 0.081).ConclusionsThe lack of a strong phylogenetic signal underscores the importance of factors other than stochastic genetic diversity in shaping worldwide heterogeneity in hip fracture incidence