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Myotragus balearicus is the terminal species of a Caprinae lineage that inhabited the Balearic Islands since the Messinian. Myotragus balearicus had a relatively small brain, reported to be half the size of a contemporary bovid of similar size. This study presents a reassessment of its brain size and anatomy. We demonstrate that the brain of M. balearicus is only 17% smaller when compared to Late Miocene taxa. Since the ancestors of M. balearicus were isolated on the Balearics in the Late Miocene, we deduce that the small brain size of M. balearicus is a feature largely retained from its continental ancestor and only partially the result of geographic isolation. The reduction in brain size can be attributed to reduction of the occipital region. We hypothesise that neuroanatomical changes during the evolutionary process of dwarfism were likely influenced by the absence of ecologically relevant predators. [ABSTRACT FROM AUTHOR]

Brain size variability in primates has been attributed to various domain-specific socio-ecological factors. A recently published large-scale study of short-term memory abilities in 41 primate species (ManyPrimates 2022 Anim. Behav. Cogn. 9, 428–516. (doi:10.26451/abc.09.04.06.2022)) did not find any correlations with 11 different proxies of external cognitive demands. Here, we found that the interspecific variation in test performance shows correlated evolution with total brain size, with the relationship becoming tighter as species with small sample sizes were successively removed, whereas it was not predicted by the often-used encephalization quotient. In a subsample, we also found that the sizes of brain regions thought to be involved in short-term memory did not predict performance better than overall brain size. The dependence on brain size suggests that domain-general cognitive processes underlie short-term memory as tested by ManyPrimates. These results support the emerging notion that comparative studies of brain size do not generally identify domain-specific cognitive adaptations but rather reveal varying selections on domain-general cognitive abilities. Finally, because attentional processes beyond short-term memory also affect test performance, we suggest that the delayed response test can be refined.

Introduction: comparative anatomy provides empirical facts for the classification of biological species on the basis of similarities or diversities of their anatomical characteristics. Animal models, especially rodents, are imperative tools for neuroscience research useful in elucidating brain pathologies. This study comparatively characterizes the anatomical features of the cerebrum of some rodent species; Wistar rat, Cavia porcellus, and Oryctolagus cuniculus using morphologic and microscopic assessments. Material and Methods: nine adult rodents (n= 3/species): Wistar rat, guinea pig (Cavia porcellus), and rabbit (Oryctolagus cuniculus) were used. Morphological and microscopic assessments including morphometrics of brain dimensions, gyrification, encephalization quotient (EQ), histology, and histometry of cerebral M1 region were conducted and features compared amongst species. Results: morphologically, brain dimensions revealed higher (p<0.05) values for rabbits among the rodent species. Gyrification was observed on the dorsal surface of cerebral hemispheres of the rodents, except in rats. Guinea pigs had the highest (p<0.05) EQ levels for species intelligence. Microscopically, layers III and V of cerebral M1 revealed similar population of cell types in all species. Histometric characteristics of pyramidal neurons in layer V were different (p<0.05) amongst the species with higher values in rabbits. No remarkable difference in cell distribution of cerebral M1 in layers III and V amongst the species. Conclusion: there exists morphologic variation in the brain features of compared rodent species and a small-scale variation in the cytoarchitectural features of the M1 cerebrum of the species. Results obtained are beneficial in identifying suitable species as potential models for certain neuroscience research. [ABSTRACT FROM AUTHOR]

Flying squirrels (Sciurinae, Pteromyini) are the most successful group of gliding mammals. However, their fossil record mostly consists of isolated dental remains that provide very limited insights into their palaeobiology and evolution. The first skeleton of a fossil flying squirrel, belonging to the species Miopetaurista neogrivensis, has been described only recently. It presents all the diagnostic gliding‐related postcranial features of its extant relatives and shows that this group has undergone very little morphological change for almost 12 myr. However, the associated cranium is badly crushed, and particular details of the cranial morphology cannot be described. Here, we describe a well‐preserved cranium of the closely related Miopetaurista crusafonti from 12.5–12.0 Ma from Bavaria (Germany). Its cranial morphology is found to be almost identical to extant large flying squirrels, even in details such as the position of the foramina. The virtual endocast also shows close affinities to living large flying squirrels in morphology and in the relative volume of different brain regions, showing diagnostic features such as the size reduction of petrosal lobules and olfactory bulbs. However, the encephalization quotient (EQ) and neocortical ratio are lower than observed in extant flying squirrels. EQ is known to increase through time in squirrels, but might also be related to locomotion, given that arboreal and gliding squirrels display higher EQs than terrestrial ones. Because Miopetaurista was certainly a glider, its comparatively lower EQ and neocortical size support the existence of an independent trend of increasing EQ and neocortical complexity in this flying squirrel subclade. [ABSTRACT FROM AUTHOR]

Abstract Objective Dogs are a breed of animals that play important roles in security service, companionship, hunting, guard, work and models of research for application in humans. Intelligence is the key factor to success in life, most especially for dogs that are used for security purposes at the airports, seaports, public places, houses, schools and farms. However, it has been reported that there is correlation between intelligence, body weight, height and craniometry in human. In view of this, literatures were searched on body weight, height and body surface areas of ten dogs with intent to determining their comparative level of intelligence using encephalization quotient. Results Findings revealed that dogs have relationship of brain allometry with human as proven by encephalization quotient $$\left( {{\text{EQ}}} \right)\, = \,{\text{Brain Mass}}/0.{14}\, \times \,{\text{Body weight}}^{{0.{528}}} ,{\text{ Brain Mass}}/0.{12}\, \times \,{\text{Body Weight}}^{{0.{66}}}$$ EQ = Brain Mass / 0.14 × Body weight 0.528 , Brain Mass / 0.12 × Body Weight 0.66 and Brain Mass (E) = kpβ, where p is the body weight; k = 0.14 and β = 0.528, respectively. Saganuwa’s formula yielded better results as compared with the other formulas. Dogs with body surface area (BSA), weight and height similar to that of human are the most intelligent. Doberman pinscher is the most intelligent followed by German shepherd, Labrador retriever, Golden retriever, respectively.

The sperm whale Physeter macrocephalus (Linnaeus, 1758) is the largest toothed whales and possesses the highest absolute values for brain weight on the planet (together with the killer whale Orcinus orca). Former calculations of the encephalization quotient (EQ), which is used to compare brain size of different mammalian species, showed that the sperm whale brain is smaller than expected for its body mass. However, the data reported in the literature and formerly used to calculate the sperm whale EQ suffered from a potential bias due to the tendency to measure mostly larger males of this extreme sexually dimorphic species. Accordingly, we found that the brains of female sperm whales are close to the absolute weight range of the males, but, given the much lower body mass of females, their EQ results more than double of what reported before for the whole species, and is thus nearly into the primate range (female EQ = 1.28, male EQ = 0.56). This sexual dimorphism is unique among mammals. Female sperm whales live in large families in which social interactions and inter-individual communication are essential, while adult males live solitarily. Thus the particular sex-specific behavior of SWs may have led to a maternally-driven social evolution, and eventually contributed to achieve female EQ values (but not male EQs) among the highest ever calculated for mammals with respect to their large body mass.

Scientists have long struggled to establish how larger brains translate into higher cognitive performance across species. While absolute brain size often yields high predictive power of performance, its positive correlation with body size warrants some level of correction. It is expected that larger brains are needed to control larger bodies without any changes in cognitive performance. Potentially, the mean value of intraspecific brain-body slopes provides the best available estimate for an interspecific correction factor. For example, in primates, including humans, an increase in body size translates into an increase in brain size without changes in cognitive performance. Here, we provide the first evaluation of this hypothesis for another clade, teleost fishes. First, we obtained a mean intraspecific brain-body regression slope of 0.46 (albeit with a relatively large range of 0.26–0.79) from a dataset of 51 species, with at least 10 wild adult specimens per species. This mean intraspecific slope value (0.46) is similar to that of the encephalisation quotient reported for teleosts (0.5), which can be used to predict mean cognitive performance in fishes. Importantly, such a mean value (0.46) is much higher than in endothermic vertebrate species (≤0.3). Second, we used wild-caught adult cleaner fish Labroides dimidiatus as a case study to test whether variation in individual cognitive performance can be explained by body size. We first obtained the brain-body regression slope for this species from two different datasets, which gave slope values of 0.58 (MRI scan data) and 0.47 (dissection data). Then, we used another dataset involving 69 adult cleaners different from those tested for their brain-body slope. We found that cognitive performance from four different tasks that estimated their learning, numerical, and inhibitory control abilities was not significantly associated with body size. These results suggest that the intraspecific brain-body slope captures cognitive equivalence for this species. That is, individuals that are on the brain-body regression line are cognitively equal. While rather preliminary, our results suggest that fish and mammalian brain organisations are fundamentally different, resulting in different intra- and interspecific slopes of cognitive equivalence. [ABSTRACT FROM AUTHOR]

Computed tomography is a non-destructive method that facilitates the accurate analysis of the internal structures of fossils. Several paleoneurological studies concerning derived non-mammaliaform cynodonts, mammaliaforms and basal mammals using this technique have been published. However, little remains known regarding the brain anatomy of basal Cynodontia. Thus, it is relevant to increase knowledge concerning the basal members of this clade to obtain a better understanding of brain evolution during the descent of mammals from non-mammaliaform cynodonts. Therefore, the present study involved analysing the digital endocasts of two non-mammaliaform cynodonts (Probelesodon kitchingi and Massetognathus ochagaviae). To assess the rate of brain development, the encephalisation quotients for these species were calculated and compared with previous data. Compared to a previous study on the brain endocasts of Probelesodon sp. and Massetognathus sp. from Argentina, digital endocasts of the Brazilian specimens revealed new brain morphology features for these genera. Additionally, the 3D digital endocasts and EQ estimates are relevant for assessing intraspecific variation and possible ontogenetic changes in these fossil taxa. [ABSTRACT FROM AUTHOR]

Baleen whales are considered underencephalized mammals due to their reduced brain size with respect to their body size (encephalization quotient [EQ] << 1). Despite their low EQ, mysticetes exhibit complex behavioral patterns in terms of motor abilities, vocal repertoire, and cultural learning. Very scarce information is available about the morphological evolution of the brain in this group; this makes it difficult to investigate the historical changes in brain shape and size in order to relate the origin of the complex mysticete behavioral repertoire to the evolution of specific neural substrates. Here, the first description of the virtual endocast of a fossil balaenopterid species, Marzanoptera tersillae from the Italian Pliocene, reveals an EQ of around 3, which is exceptional for baleen whales. The endocast showed a morphologically different organization of the brain in this fossil whale as the cerebral hemispheres are anteroposteriorly shortened, the cerebellum lacks the posteromedial expansion of the cerebellar hemispheres, and the cerebellar vermis is unusually reduced. The comparative reductions of the cerebral and cerebellar hemispheres suggest that the motor behavior of M. tersillae probably was less sophisticated than that exhibited by the extant rorqual and humpback species. The presence of an EQ value in this fossil species that is around 10 times higher than that of extant mysticetes opens new questions about brain evolution and provides new, invaluable information about the evolutionary path of morphological and size change in the brain of baleen whales. [ABSTRACT FROM AUTHOR]

Both absolute and relative brain sizes vary greatly among and within the major vertebrate lineages. Scientists have long debated how larger brains in primates and hominins translate into greater cognitive performance, and in particular how to control for the relationship between the noncognitive functions of the brain and body size. One solution to this problem is to establish the slope of cognitive equivalence, i.e., the line connecting organisms with an identical bauplan but different body sizes. The original approach to estimate this slope through intraspecific regressions was abandoned after it became clear that it generated slopes that were too low by an unknown margin due to estimation error. Here, we revisit this method. We control for the error problem by focusing on highly dimorphic primate species with large sample sizes and fitting a line through the mean values for adult females and males. We obtain the best estimate for the slope of circa 0.27, a value much lower than those constructed using all mammal species and close to the value expected based on the genetic correlation between brain size and body size. We also find that the estimate of cognitive brain size based on cognitive equivalence fits empirical cognitive studies better than the encephalization quotient, which should therefore be avoided in future studies on primates and presumably mammals and birds in general. The use of residuals from the line of cognitive equivalence may change conclusions concerning the cognitive abilities of extant and extinct primate species, including hominins. [ABSTRACT FROM AUTHOR]

Brain size variability in primates has been attributed to various domain-specific socio-ecological factors. A recently published large-scale study of short-term memory abilities in 41 primate species (ManyPrimates 2022 Anim. Behav. Cogn. 9, 428-516. (doi:10.26451/abc.09.04.06.2022)) did not find any correlations with 11 different proxies of external cognitive demands. Here, we found that the interspecific variation in test performance shows correlated evolution with total brain size, with the relationship becoming tighter as species with small sample sizes were successively removed, whereas it was not predicted by the often-used encephalization quotient. In a subsample, we also found that the sizes of brain regions thought to be involved in short-term memory did not predict performance better than overall brain size. The dependence on brain size suggests that domain-general cognitive processes underlie short-term memory as tested by ManyPrimates. These results support the emerging notion that comparative studies of brain size do not generally identify domain-specific cognitive adaptations but rather reveal varying selections on domain-general cognitive abilities. Finally, because attentional processes beyond short-term memory also affect test performance, we suggest that the delayed response test can be refined., Competing Interests: We declare we have no competing interests., (© 2024 The Authors.)

Depending on the presence or absence of sulci and convolutions, the brains of mammals are classified as gyrencephalic or lissencephalic. We analyzed the encephalic anatomy of the hystricomorph rodent Lagostomus maximus in comparison with other evolutionarily related species. The encephalization quotient (EQ), gyrencephaly index (GI), and minimum cortical thickness (MCT) were calculated for the plains vizcacha as well as for other myomorph and hystricomorph rodents. The vizcacha showed a gyrencephalic brain with a sagittal longitudinal fissure that divides both hemispheres, and 3 pairs of sulci with bilateral symmetry; that is, lateral-rostral, intraparietal, and transverse sulci. The EQ had one of the lowest values among Hystricomorpha, while GI was one of the highest. Besides, the MCT was close to the mean value for the suborder. The comparison of EQ, GI, and MCT values between hystricomorph and myomorph species allowed the detection of significant variations. Both EQ and GI showed a significant increase in Hystricomorpha compared to Myomorpha, whereas a Pearson's analysis between EQ and GI depicted an inverse correlation pattern for Hystricomorpha. Furthermore, the ratio between MCT and GI also showed a negative correlation for Hystricomorpha and Myomorpha. Our phylogenetic analyses showed that Hystricomorpha and Myomorpha do not differ in their allometric patterning between the brain and body mass, GI and brain mass, and MCT and GI. In conclusion, gyrencephalic neuroanatomy in the vizcacha could have developed from the balance between the brain size, the presence of invaginations, and the cortical thickness, which resulted in a mixed encephalization strategy for the species. Gyrencephaly in the vizcacha, as well as in other Hystricomorpha, advocates in favor of the proposal that in the more recently evolved Myomorpha lissencephaly would have arisen from a phenotype reversal process. [ABSTRACT FROM AUTHOR]

One hundred fifty day-old sexed Vanaraja chicks (75 male + 75 female) were taken as experimental birds. Dissection of cranium was performed carefully and study of gross morphology of brain was undertaken at different ages in male and female birds. The brain in situ appeared like a ‘spade’ symbol in playing card but it appeared rather wider and globular in both sexes. The cerebrum varied from pear to oval or even globular in shape in both sexes. On dorsal view, the cerebral hemispheres appeared moderately convex and smooth surfaced. On ventral surface, ill-developed olfactory lobes were observed anteriorly on either side of the median fissure in both male and female Vanaraja birds. The hippocampus was located transversely to the posterior one third parts of both cerebral hemispheres. Duncan’s EQ ranged from 5.801 ± 0.514 (T3-Male) to 5.944 ± 0.451 (T1-Female) on 21st day. There was significant decrease (p

The question of what has shaped primates' (and other species') cognitive capacities, whether technical or social demands, remains a hot topic of inquiry. Indeed, a key area of study within the field of comparative psychology in the last few decades has been the focus on social life as a driving force behind the evolution of cognition, studied from behavioral and neurological perspectives and from theoretical and empirical perspectives. Reflecting on contemporary studies of primate social cognition specifically, one cannot ignore the book, Machiavellian Intelligence, coedited by Richard Byrne and Andrew Whiten (Byrne & Whiten, 1988a). It is a keystone for the field: The volume as a whole has been cited over 3,000 times, without even including citations to individual chapters. This year, 2018, is the 30th anniversary of the first publication of Machiavellian Intelligence, and with this special issue of the Journal of Comparative Psychology, we mark that milestone. The key concept put forth in Machiavellian Intelligence was that primates' sociocognitive abilities were shaped by the complex social worlds that they inhabited, rather than the technical or foraging challenges that they faced, as had previously been posited. In this issue, we consider the strength of the Machiavellian intelligence hypothesis 30 years on to explain primate social cognition, and we consider its applicability to nonprimate species and to other cognitive domains. [ABSTRACT FROM AUTHOR]

The brain of Surti buffaloes presents many cortical foldings. These are called gyrification. In the present study on brain of 12 Surti buffaloes, the folded cerebral hemispheres presented various sulci and gyri of different sizes. Gyrification Index (GI) was measured by the sum of the complete exposed surface and superficially exposed surface of cerebral cortex. The overall mean value of gyrification index of both of cerebral hemispheres was 2.52±0.02. The Encephalization Quotient (EQ) is the ratio of brain mass to body mass, which gives rough estimate of the intelligence of the Surti buffaloes. The overall mean value of encephalization quotient of Surti buffaloes was found to be 0.74. [ABSTRACT FROM AUTHOR]

Abstract: Understanding what factors drive patterns of genetic diversity is a central aspect of many biological questions, ranging from the inference of historical demography to assessing the evolutionary potential of a species. However, as a larger number of datasets have become available, it is becoming clear that the relationship between the characteristics of a species and its genetic diversity is more complex than previously assumed. This may be particularly true for cetaceans, due to their relatively long lifespans, long generation times, complex social structures, and extensive ranges. In this study, we used microsatellite and mitochondrial DNA data from a systematic literature review to produce estimates of diversity for both markers across 42 cetacean species. Factors relating to demography, distribution, classification, biology, and behavior were then tested using phylogenetic methods and linear models to assess their relative influence on the genetic diversity of both marker types. The results show that while relative nuclear diversity is correlated with population size, mitochondrial diversity is not. This is particularly relevant given the widespread use of mitochondrial DNA to infer historical demography. Instead, mitochondrial diversity was mostly influenced by the range and social structure of the species. In addition to population size, habitat type (neritic vs. oceanic) had a significant correlation with relative nuclear diversity. Combined, these results show that many often‐unconsidered factors are likely influencing patterns of genetic diversity in cetaceans, with implications regarding how to interpret, and what can be inferred from, existing patterns of diversity. [ABSTRACT FROM AUTHOR]

Supplying the central nervous system with oxygen and glucose for metabolic activities is a critical function for all animals at physiologic, anatomical, and behavioral levels. A relatively proximate challenge to nourishing the brain is maintaining adequate blood flow. Euarchontans (primates, dermopterans and treeshrews) display a diversity of solutions to this challenge. Although the vertebral artery is a major encephalic vessel, previous research has questioned its importance for irrigating the cerebrum. This presents a puzzling scenario for certain strepsirrhine primates (non-cheirogaleid lemuriforms) that have reduced promontorial branches of the internal carotid artery and no apparent alternative encephalic vascular route except for the vertebral artery. Here, we present results of phylogenetic comparative analyses of data on the cross-sectional area of bony canals that transmit the vertebral artery (transverse foramina). These results show that, across primates (and within major primate subgroups), variation in the transverse foramina helps significantly to explain variation in forebrain mass even when variation in promontorial canal cross-sectional areas are also considered. Furthermore, non-cheirogaleid lemuriforms have larger transverse foramina for their endocranial volume than other euarchontans, suggesting that the vertebral arteries compensate for reduced promontorial artery size. We also find that, among internal carotid-reliant euarchontans, species that are more encephalized tend to have a promontorial canal that is larger relative to the transverse foramina. Tentatively, we consider the correlation between arterial canal diameters (as a proxy for blood flow) and brain metabolic demands. The results of this analysis imply that human investment in brain metabolism (∼27% of basal metabolic rate) may not be exceptional among euarchontans. [ABSTRACT FROM AUTHOR]

Sixty-day-old chicks from the commercial broiler strain, Vencobb, and 60-day-old backyard Vanaraja chickens, were selected as experimental birds for assessing learning and cognitive performance. Learning and cognitive ability were assessed on the basis of maze trial performance, self-recognition trial (SRT), detour trial (DT), tonic immobility (TI) trial, serum leptin concentration, and encephalization quotient (EQ). The mazes were prepared by using locally available cardboard, papers, and bamboo strips. Three maze trials—T maze trial, Y maze trial, and radial maze trial—were performed. Birds were trained from the second to 10th day for maze tests. The maze test schedules started from 11th day, and data were taken 11th-17th day, 25th-31st day, and 39th-45th day in trial I, trial II, and trial III schedules, respectively. The response of birds to different maze tests and performance in different cognitive trials were assessed on the basis of latency in time to acquire the food and complete the tasks. At the end of the trials, serum leptin concentration was assayed. EQ was calculated by Jerison's formula and Cuvier's formula. Vencobb birds showed a better response to different cognitive and learning trials. In T maze trials, the Vencobb variety performed significantly better ( P < 0.05) than Vanaraja birds (trial I, P = 0.001; trial II, P = 0.001; and trial III, P = 0.01). Vencobb birds, when housed in group with Vanaraja birds, performed significantly ( P < 0.05) worse in trial I ( P = 0.012), trial II ( P = 0.020), and trial III ( P = 0.045). In the Y maze trial, homogeneously housed Vencobb birds performed significantly better ( P < 0.05) than did Vanaraja birds (trial I, P = 0.04; trial II, P = 0.01). Vanaraja birds performed significantly ( P < 0.05) better when they were homogeneously housed than mixed housed (trial I, P = 0.10; trial II, P = 0.001; and trial III, P = 0.008). There was significant improvement ( P < 0.05) in the performance of Vencobb birds with advancement of age from trial I to trial II in all cases (homogenous group, P = 0.012; mixed group, P = 0.010). Similarly, significant ( P < 0.05) improvement in performance was observed in homogeneously housed Vanaraja birds (trial I-II, P = 0.012; trial II-III, P = 0.040) and mixed housed Vanaraja birds (trial I-II, P = 0.042; trial II-III, P = 0.021). In the case of the R maze trial, Vencobb birds (homogenous) performed significantly ( P < 0.05) better as compared with Vanaraja birds (homogenous) in all 3 trials (trial I, P = 0.01; trial II, P = 0.001; and trial III, P = 0.03). In homogeneous housing system, the performance of Vencobb birds was significantly better ( P < 0.05) than Vanaraja birds in SRT (trial I, P = 0.01; trial II, P = 0.001; and trial III, P = 0.001), whereas Vanaraja birds performed significantly better ( P < 0.05) than Vencobb birds in the DT (trial I, P = 0.05; trial II, P = 0.05; and trial III, P = 0.07) and TI trial (trial I, P = 0.02; trial II, P = 0.05; and trial III, P = 0.04). In the SRT test, Vanaraja birds performed significantly better ( P < 0.05) in mixed housing than in homogeneous groups (trial II, P = 0.01; trial III, P = 0.01). Vencobb birds showed a significant improvement ( P < 0.05) from trial I to trial II in homogeneous and mixed housing ( P = 0.04 and P = 0.02). In mixed housing, significant improvement ( P < 0.05) in the performance of Vanaraja birds was seen from trial I to trial II ( P = 0.001). In DT, homogeneous Vencobb birds (trial I) performed significantly worse ( P < 0.05) as compared with mixed grouped birds ( P = 0.05). In case of Vanaraja birds, mixed housed birds showed significantly ( P < 0.05) better performance than did homogeneous birds ( P = 0.001) in trial I. In the TI trial, there was significant improvement ( P < 0.05) in the performance from trial I to trial II in homogeneous Vencobb ( P = 0.04) and mixed Vanaraja birds ( P = 0.05). The EQ maximum was 2.31 in intelligent or superior birds and 1.85 in dull birds. The cognitively superior Vencobb birds showed a significantly higher level of serum leptin concentration than did the dull birds (0.78 ± 0.12 vs. 0.42 ± 0.08 ng/mL, P = 0.02), a result similar to that in Vanaraja birds (1.03 ± 0.13 vs. 0.62 ± 0.06 ng/mL, P = 0.01). It may be concluded that the genetics of the birds affects cognitive and learning ability. Mixed group housing negatively affects the cognitive abilities of birds. Jerison's formula is more highly correlated with brain weight than the traditional Cuvier's equation. With the advancement of age, spatial memory involved in gathering and processing improves. [ABSTRACT FROM AUTHOR]

In this essay, we explore the origins of the ability to produce surplus value through human labor. The main hypothesis is that the safety factor for energy capacity in humans determines the surplus value of human labor in human societies. We estimate the safety factor for Homo sapiens to be around 2.78. This is based on the rise of the encephalization quotient from 2.5 in Australopithecus africanus to 5.8 in H. sapiens, and we assume this rise is matched by a rise in the safety factor from 1.2 to 2.78. Being a communal species compels human individuals to produce both their personal and their community's energy need. The possible correlation between Dunbar's number and the safety factor of energy production capacity provides a very essential feature of human labor, namely 'surplus value'. The average labor activity of a modern human is sufficient to provide energy for two to three people's energy burden in a community. Human labor not only produces the energy for survival of an individual but also produces a surplus due to the safety factor. Therefore, work activity of an individual enables them to supply more than they need for themselves as a value. [ABSTRACT FROM AUTHOR]

Mammals that possess elaborate antipredator defences such as body armour, spines and quills are usually well protected, intermediate in size, primarily insectivorous and live in simple open environments. The benefits of such defences seem clear and may relax selection on maintaining cognitive abilities that aid in vigilance and predator recognition, and their bearers may accrue extensive production and maintenance costs. Here, in this comparative phylogenetic analysis of measurements of encephalization quotient and morphological defence scores of 647 mammal species representing nearly every order, we found that as lineages evolve stronger defences, they suffer a correlated reduction in encephalization. The only exceptions were those that live in trees--a complex three-dimensional world probably requiring greater cognitive abilities. At the proximate level, because brain tissue is extremely energetically expensive to build, mammals may be trading off spending more on elaborate defences and saving by building less powerful brains. At the ultimate level, having greater defences may also reduce the need for advanced cognitive abilities for constant assessment of environmental predation risk, especially in simple open environments. [ABSTRACT FROM AUTHOR]

The tight brain-body allometry across mammals and primates has motivated and informed many hypotheses about brain evolution in humans and other taxa. While a 2/3 or a 3/4 scaling is often at the core of such research, such exponents are derived from estimates based on particular statistical and evolutionary assumptions without careful consideration of how either may influence findings. Here we quantify primate brain-body allometry using phylogenetic comparative methods based on models of both adaptive and constrained evolution, and estimate and account for observational error in both response and predictor variables. Our results supported an evolutionary model in which brain size is directly constrained to evolve in unison with body size, rather than adapting to changes in the latter. The effects of controlling for phylogeny and observation error were substantial, and our analysis yielded a novel 3/5 scaling exponent for primate brain-body evolutionary allometry. Using this exponent with the latest brain- and body-size estimates to calculate new encephalization quotients for apes, humans, and fossil hominins, we found early hominins were substantially more encephalized than previously thought. [ABSTRACT FROM AUTHOR]

The sperm whale (Physeter macrocephalus, Linnaeus 1758) possesses the largest brain that ever existed. Relatively few authors have dealt with it and the available descriptions are heterogeneous, with only few data about brain weight or gross anatomy. In fact the central nervous system of large cetaceans is quite difficult to obtain, given the huge body size and the low frequency of strandings of recently dead individuals. Furthermore, since the skull of the sperm whale underwent an extreme transformation for the accommodation of the spermaceti organ, the cranial cavity is surrounded by thick layers of bone and thus difficult to reach under field conditions. We recently had the chance to extract the brain from two stranded sperm whales whose bodies were in good condition. In the present note we describe the main macroscopic characteristics of the sperm whale brain, including its weight and Encephalization Quotient, review the available literature, and describe a possible new approach to the removal and preservation of the organ under field conditions.

Ornithopod dinosaurs were a successful group before they became extinct at the end of the Cretaceous. They were present on every continent, though they were rare in the Southern Hemisphere. We present the results of our work on the brain of these dinosaurs as an attempt to determine which evolutionary trends affected it. Old and new technologies allow us to peer into the skull of long extinct animals and retrieve information about their brain. First we provide a short description of the brain of ornithopod dinosaurs from Europe and Asia, then we sum up the characteristics that can be gathered from it. The presence of valleculae helps us to assess the actual size of the brain with more confidence. The olfactory peduncles are large and these animals had a good sense of smell. There is a trend toward an increase in the size of the cerebral hemispheres, and a more straight-lined brain. The latter can be the result of the ontogeny and the size achieved by the adult animal on the development of the brain. Other characteristics, like the development of the cerebral hemispheres and the encephalization quotient, allude to Hadrosauridae having had cognitive abilities more developed than previously assumed. This is in adequacy with other data from the physical characteristics (e.g., crests) and the social life (e.g., living in herds, communal nests) of these dinosaurs, which denote high and complex behaviors like care for their young, sexual courtship, and gregariousness., (Copyright © 2023 Elsevier B.V. All rights reserved.)

All modern mammals are descendants of the paraphyletic non-mammaliaform Synapsida, colloquially referred to as the "mammal-like reptiles." It has long been assumed that these mammalian ancestors were essentially reptile-like in their morphology, biology, and behavior, i.e., they had a small brain, displayed simple behavior, and their sensory organs were unrefined compared to those of modern mammals. Recent works have, however, revealed that neurological, sensory, and behavioral traits previously considered typically mammalian, such as whiskers, enhanced olfaction, nocturnality, parental care, and complex social interactions evolved before the origin of Mammaliaformes, among the early-diverging "mammal-like reptiles." In contrast, an enlarged brain did not evolve immediately after the origin of mammaliaforms. As such, in terms of paleoneurology, the last "mammal-like reptiles" were not significantly different from the earliest mammaliaforms. The abundant data and literature published in the last 10 years no longer supports the "three pulses" scenario of synapsid brain evolution proposed by Rowe and colleagues in 2011, but supports the new "outside-in" model of Rodrigues and colleagues proposed in 2018, instead. As Mesozoic reptiles were becoming the dominant taxa within terrestrial ecosystems, synapsids gradually adapted to smaller body sizes and nocturnality. This resulted in a sensory revolution in synapsids as olfaction, audition, and somatosensation compensated for the loss of visual cues. This altered sensory input is aligned with changes in the brain, the most significant of which was an increase in relative brain size., (Copyright © 2023 Elsevier B.V. All rights reserved.)

During the period of 1958 and 1960, the richest sample of Palaeoloxodon ex gr. P. falconeri (104 individuals) was recovered from Spinagallo cave (Syracuse, Hyblean Plateau, SE Sicily). Subsequently, several composite skeletons were reconstructed. Four of them are today exhibited at the Paleontological Museum of Department of Earth Sciences of Sapienza University of Rome (MPUR). Three of the skeletons representing an adult male (MPUR/V n1), an adult female (MPUR/V n2) and a calf (MPUR/V n3), were analysed in order to reconstruct the physical appearance and estimate the body mass of the species. The rigorous skeletal restorations suggest that the living males approached a height of 100 cm at the shoulder and over 300 kg in body mass, whereas females were around 80 cm high and around 165 kg. The sexual dimorphism in Palaeoloxodon ex gr. P. falconeri was concluded to be comparable to that of extant elephants. The small size probably had a direct influence in the animals' physiology and biology; including a shorter life span, rapid growth, and changes in thermoregulation mechanisms. The drastic allometric size reduction experienced by Siculo-Maltese dwarf elephants, produced noticeable changes in the skull, showing some paedomorphic features that were present in young P. antiquus and in extant juvenile elephants, and in the axial and appendicular skeleton proportions with respect to its putative mainland ancestor Palaeoloxodon antiquus. Some unique traits observed in the limb bones, suggest a more agile locomotion in P. ex gr. P. falconeri than other elephantids. Nevertheless, the most noteworthy change is the positive allometric increase of the brain case. The large change in brain proportions was related to the need to maintain the minimal functional volume of the brain when the size of the skull was drastically reduced. [ABSTRACT FROM AUTHOR]

Anthracotheres are a fossil family of ' Suiformes' from the Old World, North and Central America. They are known from the middle Eocene to the late Pliocene, and are suggested to be the stem group of Hippopotamidae. Yet, their soft anatomy remains poorly known. In this study we describe the virtual endocast of the late Oligocene anthracothere Microbunodon minimum, reconstructed using microtomography, as well as the natural endocast of Merycopotamus medioximus from the late Miocene. These are the first anthracothere endocasts ever described. Particular attention is given to the relative proportions of the brain, the neocortex, the cerebellum and the olfactory bulbs. The 'backward shift' of the pituitary of M. minimum, and the possible presence of a K lobe in M. medioximus, is discussed. Previous statements that some endocranial characters were subject to convergence among mammals are also corroborated. [ABSTRACT FROM AUTHOR]

The diversity of the order Cingulata is much higher in the fossil record than that represented by the extant species. While pampatheres, one of its extinct groups, are superficially similar to armadillos, recent phylogenetic analysis grouped them with glyptodonts in the clade Glyptodonta. We describe here the first digital endocranial cast of a pampathere, Pampatherium humboldtii, from the Late Pleistocene of Uruguay and compare its morphology with that of glyptodonts and extant and fossil armadillos. Some of the characteristics observed are more similar to those of glyptodonts than to those seen in armadillos. The endocranial cast of Pampatherium has large pedunculate olfactory bulbs, a relative small cerebrum with only one cortical sulcus and a large cerebellum. Although all groups of cingulates, both extant and extinct, have a similar relative brain size, the relative brain size of pampatheres is larger than in glyptodonts and close to that of extant armadillos, The endocast morphology and the analysis of relative brain size of Pampatherium are congruent with their close affinity to glyptodonts and their inclusion in the clade Glyptodonta, although in a family of its own. [ABSTRACT FROM AUTHOR]

The horse is a common domestic animal whose anatomy has been studied since the XVI century. However, a modern neuroanatomy of this species does not exist and most of the data utilized in textbooks and reviews derive from single specimens or relatively old literature. Here, we report information on the brain of Equus caballus obtained by sampling 131 horses, including brain weight (as a whole and subdivided into its constituents), encephalization quotient (EQ), and cerebellar quotient (CQ), and comparisons with what is known about other relevant species. The mean weight of the fresh brains in our experimental series was 598.63 g (SEM ± 7.65), with a mean body weight of 514.12 kg (SEM ± 15.42). The EQ was 0.78 and the CQ was 0.841. The data we obtained indicate that the horse possesses a large, convoluted brain, with a weight similar to that of other hoofed species of like mass. However, the shape of the brain, the noteworthy folding of the neocortex, and the peculiar longitudinal distribution of the gyri suggest an evolutionary specificity at least partially separate from that of the Cetartiodactyla (even-toed mammals and cetaceans) with whom Perissodactyla (odd-toed mammals) are often grouped. © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]