Selection for increased encephalization in humans necessitated extensive brain growth after birth. To estimate changes in rates of growth and corresponding shape changes during gestation and infancy, chord and arc distances were obtained from the frontal, parietal, and occipital bones of 44 human fetuses, neonates, and infants (one year old and younger). Rates of growth in chord and arc measurements were calculated and compared using linear regression of log-transformed variables, followed by ANCOVA. Curvature of bone lengths and widths were estimated by chord/arc indices. Fetal rates of cranial growth were significantly slower while the fetal frontal and occipital bones were significantly more curved than those of infants. Fetal rates of cranial growth decrease during the first six postnatal months, in conjunction with rapid changes in shape, except for parietal superior-inferior height where bossing of the bone is similar in fetuses and neonates.

<p>The pace of life history is highly variable across mammals, and several evolutionary biologists have theorized that the tempo of a species' life history is set by external factors. These factors, such as food availability and predation pressure, determine mortality rates. In turn, mortality rate determines the age at maturity. High mortality rate results in early age at maturity; individuals must grow and reproduce quickly because of the high risk of death. Conversely, a low mortality rate is allows individuals to prolong their growth period and reproduce slowly. This theory assumes that growth rates are constant across species, and thus body size is determined by mortality rates.</p><p>This project posits that the intrinsic characteristics of species set the pace of life history. Among anthropoids, there is a great deal of variation in growth rates and the pace of life history relative to body size. The hypotheses proposed by this project state that the degree of encephalization in a species determines the growth rates, the length of the growth period, and the adult lifespan. Growing a large brain is costly and requires a prolonged period of development. However, a large brain has the benefit of reducing mortality by facilitating cognitive strategies for food procurement and predator avoidance. This cost/benefit balance results in the pattern of life-history variation in which mortality rates are correlated with the length of the growth period. However, the causal arrows are reversed; instead of the mortality rate determining the age at maturity and consequently the size of the species, the relative brain size of the anthropoid determines the mortality rate and the age maturity.</p><p>These hypotheses were tested by determining the body and brain growth trajectories of thirteen anthropoids, and compiling life-history data from long-term studies of these species in the wild. Multi-variate analyses demonstrated that extensive brain growth, whether through prolonged duration or rapid growth rates, results in slow body-growth rates during the juvenile period and delayed age at maturity. In addition, encephalization results in longer adult lifespan. Therefore, this project demonstrated that intrinsic characteristics of anthropoid species determine the pace of their life histories.</p> / Dissertation

<p>Fossil taxa are crucial to studies of brain evolution, as they allow us to identify evolutionary trends in relative brain size and brain shape that may not otherwise be identifiable in comparative studies using only extant taxa, owing to multiple events of parallel encephalization among primate clades. This thesis combines indirect and direct approaches to understanding primate evolution, by evaluating variation in the endocranial morphology of extant primates and their fossil representatives. I use a comparative approach to examine the relationships between interspecific adult endocranial volume and shape, and brain evolution and cranial form among extant primate clades and their fossil representatives. The associations are evaluated via phylogenetically informed statistics perfomed on volumetric measurements and three-dimensional geometric morphometric analyses of virtual endocasts constructed from micro-CT scans of primate crania. Fossil taxa included in these analyses are: 1) anthropoids Parapithecus, Aegyptopithecus (Early Oligocene, Egypt), Homunculus and Tremacebus (Early Miocene, Argentina), and 2) Eocene euprimates Adapis and Leptadapis (Eocene adapoids, France), and the Rooneyia (Eocene omomyoid, Texas). </p><p>The first part of this work (Chapter 2) explores variation in residual mass of brain components (taken from the literature) among primates, and evaluates the correlated evolution of encephalization and brain proportions with endocast shape, quantified via three-dimensional geometric morphometric techniques. Analyses reveal a broad range of variation in endocast shape among primates. Endocast shape is influenced by a complex array of factors, including phylogeny, body size, encephalization, and brain proportions (residual mass of brain components). The analysis supports previous research, which concludes that anthropoids and tarsiers (Haplorhini) share the enlargement of several key brain regions including the neocortex and visual systems, and a reduction of the olfactory system. Anthropoids further differ from strepsirrhines in endocranial features associated with encephalization--a more flexed brain base, an inferiorly deflected olfactory fossa--and those associated with brain proportions--a small olfactory fossa, and a more caudally extended cerebrum that extends posteriorly past the cerebellar poles. Tarsiers are unique in having a mediolaterally broad and rostro-caudally short endocast with an attenuated anterior and middle cranial fossae. This morphology is likely related to the extreme orbital enlargement in this taxon, which limits anterior expansion of the endocranium. Finally, despite the correlation between residual endocranial volume and endocast shape among modern primates, early anthropoid fossils demonstrate a disconnect between these factors in sharing key features of endocast shape with extant anthropoids at a relatively small brain size. </p><p>The second part of this thesis (Chapter 3) explores the relationship between craniofacial organization--cranial base angle, facial size, facial hafting--and encephalization via the lens of the Spatial Constraints and Facial Packing Hypotheses. These hypotheses predict that interspecific adult variation in encephalization correlates with endocranial shape such that a larger brain for a given body size will be more "globular" or spherical in shape. These hypotheses futher predict that basicranial angle covaries with encephalization and that the relative size of the endocranium and facial skeleton will have an antagonistic effect on basicranial angle and facial hafting. Results show that various measures of globularity have inconsistent and weak relationships to phylogeny, encephalization, and basicranial flexion, owing to a diversity of clade-specific scaling patterns between the maximum length, breadth, and width of the endocast. Among extant primates, there is weak but significant evidence to suggest that both facial size and encephalization influence variation in basicranial flexion. Considering the fossil specimens in isolation, their relative ranks in encephalization, basicranial flexion, and midline facial size and shape follow the pattern expected from the Spatial and Facial Packing Hypotheses outlined above; however, relative to modern species, the early fossil anthropoids have more flexed cranial bases and shorter facial skeletons at much smaller level of encephalization than seen in modern anthropoids. </p><p>Together, the extant data suggest a moderately conserved pattern of correlated evolution among endocranial size, endocranial shape, brain proportions, and craniofacial organization, which may explain differences in endocranial and facial shape between extant strepsirrhine and anthropoid primates; however, the fossil record for early anthropoid evolution demonstrates that a shift towards key anthropoid-like traits of the endocranium, basicranium, and facial skeleton were initiated early in anthropoid evolution, with subsequent encephalization occurring within and among members of this clade. Thus, these anthropoid cranial traits evolved in tandem with changes in the relative size of brain components, rather than absolute or relative brain size alone. Basicranial flexion, facial length and orientation are influenced by both: 1) shifts in endocranial shape associated with changes in brain proportion--accounting for the initiation of the anthropoid-like craniofacial plan early in the evolution of the clade--and 2) encephalization, which influenced subsequent morphological divergence among extant anthropoid groups.</p> / Dissertation

Submitted by PPG Zoologia (zoologia-pg@pucrs.br) on 2018-04-17T13:17:04Z No. of bitstreams: 1 Disserta??o_CAH_vfinal.pdf: 3985079 bytes, checksum: 6ad6a029bd9cffd5f9f47cd2432f0e7d (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2018-05-04T17:30:42Z (GMT) No. of bitstreams: 1 Disserta??o_CAH_vfinal.pdf: 3985079 bytes, checksum: 6ad6a029bd9cffd5f9f47cd2432f0e7d (MD5) / Made available in DSpace on 2018-05-04T17:35:13Z (GMT). No. of bitstreams: 1 Disserta??o_CAH_vfinal.pdf: 3985079 bytes, checksum: 6ad6a029bd9cffd5f9f47cd2432f0e7d (MD5) Previous issue date: 2018-02-22 / Conselho Nacional de Pesquisa e Desenvolvimento Cient?fico e Tecnol?gico - CNPq / Important studies have already been done regarding on paleoneurology of extinct animals due to the advancement of computed tomography techniques in recent years. This allowed more accurate studies and without the need to modify materials, especially non-mammaliaform cynodonts and basal mammals. However, these analyzes are limited by material preservation biases, often with absence of postcranium. Consequently, body mass estimations are required, which are necessary for calculations of quantitative analyzes regarding the evolution of the brain capacity of these animals. Considering this, in order to increase the data set about the evolution of the brain in Cynodontia, computed tomography of two skulls of the MCT/PUCRS (MCP 1600 PV Probelesodon kitchingi; MCP 3871 PV Massetognathus ochagaviae) were performed. We also calculated the specimens? encephalization quotients (EQ), with and without the olfactory bulbs, using two formulas of body mass estimation. When the necessary data were available in the literature, the EQs were calculated for other synapids for comparative purposes. In relation to the morphology of the endocranial casts, no differences were observed in relation to previous described for other eucinodonts, in which there is still no enlargement of the cerebral hemispheres, as well as a development of the cerebellar region. The EQs obtained for M. ochagaviae and P. kitchingi do not differ representatively from those previously calculated for other materials of the same genus. For the calculations with and without the olfactory bulbs the same was observed. However, when comparing the encephalization quotients obtained with the application of the four formulas, significant differences were observed between the results. Therefore, it is not possible to compare the EQs obtained with the different methods, and only one is required. / Importantes estudos j? foram realizados acerca da paleoneurologia de animais extintos gra?as ao avan?o das t?cnicas de tomografia computadorizada nos ?ltimos anos. Isso possibilitou estudos mais precisos e sem a necessidade de altera??o dos materiais, especialmente cinodontes n?o-mammaliaformes e mam?feros basais. Entretanto, estas an?lises s?o limitadas por vieses de preserva??o dos materiais, muitas vezes com aus?ncia de p?s-cr?nio. Consequentemente, s?o realizadas estimativas de massa corporal, necess?rias para os c?lculos de an?lises quantitativas da evolu??o da capacidade cerebral destes animais. Considerando isso, a fim de aumentar o conjunto de dados acerca da evolu??o do c?rebro em Cynodontia, foram realizadas tomografias computadorizadas de dois cr?nios do MCT/PUCRS (MCP 1600 PV Probelesodon kitchingi; MCP 3871 PV Massetognathus ochagaviae). Tamb?m foram calculados os quocientes de encefaliza??o (EQ) para os esp?cimes, com e sem os bulbos olfat?rios, aplicando-se quatro m?todos. Para as estimativas de massa corp?rea utilizou-se duas f?rmulas. Quando os dados necess?rios estavam dispon?veis na bibliografia, foram calculados os EQs para outros sinapsidos com fins comparativos. Em rela??o ? morfologia dos moldes endocranianos, n?o foram observadas diferen?as em rela??o ao descrito para outros eucinodontes, no qual ainda n?o h? um alargamento dos hemisf?rios cerebrais, assim como um desenvolvimento da regi?o cerebelar. Os EQs obtidos para M. ochagaviae e P. kitchingi n?o diferem de forma representativa dos previamente calculados para outros materiais de mesmos g?neros. O mesmo foi observado para os c?lculos com e sem os bulbos olfat?rios. Entretanto, ao analisar comparativamente os quocientes de encefaliza??o obtidos com a aplica??o das quatro f?rmulas, foram observadas diferen?as significativas entre os resultados. Portanto, n?o ? poss?vel a compara??o entre os EQs obtidos com os diferentes m?todos, sendo necess?ria a escolha de apenas um.

Vertebrates show dramatic interspecific variation in the size of their brains. The complexity of brains is considered to be the key factor of evolutionary success in Vertebrates, and therefore an evolutionary trend towards increasing brain size and coplexity is assumed. Large and complex brains evolved independently in birds and mammals. Birds have brains that are comparable in their relative size to the brains of mammals. However, in stark contrast to mammals, there is no general trend towards increase of brain size in birds. Relatively large brains have evolved independently in many avian lineages. Highly encephalised orders are parrots (Psittaciformes), woodpeckers and relatives (Piciformes), hornbills, hoopoe and wood hoopoes (Bucerotiformes), owls (Strigiformes), storks (Ciconiiformes) and several families of songbirds (Passeriformes), mainly bowerbirds (Ptilorhynchidae) and corvids (Corvidae). Otherhighlyencephalizedgroupsarenon-parasiticcuckoos(genusCentropus,Phaenicophaeus and Coua) and family Diomeidea and genus Pelecanus belonging to the clade water birds. Less encephalized groups include the basal lineages such as paleognaths and fowl (Galloanserae), and also pigeons (Columbiformes) and swifts, treeswifts and hummingbirds (Apodiformes). We suggest that this mosaic evolution is result of...

According to the prevailing doctrine, brain size has mainly increased throughout the evolution of mammals and reductions in brain size were rare. On the other hand, energetic costs of developing and maintaining big brain are high, so brain size reduction should occur every time when the respective selective pressure is present. Modern phylogenetic methods make it possible to test the presence of evolutionary trend and to infer the ancestral values of the trait in question based on knowledge of phylogeny and trait values for recent species. However, this approach has been rarely applied to study brain evolution so far. In this thesis, I focus on bats (Chiroptera). Bats are a suitable group for demonstrating the importance of brain size reductions. Considering their energetically demanding mode of locomotion, they are likely to have been under selection pressure for brain reduction. Furthermore, there is a large amount of data on body and brain mass of recent species available. Finally, phylogenetic relationships among bats are relatively well resolved. My present study is based on body masses and brain masses of 334 recent bat species (Baron et al., 1996) and on a phylogeny obtained by adjusting existing bat supertree (Jones et al., 2002) according to recent molecular studies. Analysing the data for...

No description available.