scholarly journals Endocranial morphology of Palaeocene Plesiadapis tricuspidens and evolution of the early primate brain

2014 ◽  
Vol 281 (1781) ◽  
pp. 20132792 ◽  
Author(s):  
Maeva J. Orliac ◽  
Sandrine Ladevèze ◽  
Philip D. Gingerich ◽  
Renaud Lebrun ◽  
Thierry Smith
Keyword(s):  
Brain Size ◽  
Brain Evolution ◽  
Primate Evolution ◽  
Brain Morphology ◽  
Micro Ct ◽  
Crown Group ◽  
Partial Reconstruction ◽  
Primate Brain ◽  
Size And Morphology ◽  
The Brain

Expansion of the brain is a key feature of primate evolution. The fossil record, although incomplete, allows a partial reconstruction of changes in primate brain size and morphology through time. Palaeogene plesiadapoids, closest relatives of Euprimates (or crown-group primates), are crucial for understanding early evolution of the primate brain. However, brain morphology of this group remains poorly documented, and major questions remain regarding the initial phase of euprimate brain evolution. Micro-CT investigation of the endocranial morphology of Plesiadapis tricuspidens from the Late Palaeocene of Europe—the most complete plesiadapoid cranium known—shows that plesiadapoids retained a very small and simple brain. Plesiadapis has midbrain exposure, and minimal encephalization and neocorticalization, making it comparable with that of stem rodents and lagomorphs. However, Plesiadapis shares a domed neocortex and downwardly shifted olfactory-bulb axis with Euprimates. If accepted phylogenetic relationships are correct, then this implies that the euprimate brain underwent drastic reorganization during the Palaeocene, and some changes in brain structure preceded brain size increase and neocortex expansion during evolution of the primate brain.

Vertebrate Evolution and Movement

2018 ◽  
Vol 3 (04) ◽  
Author(s):  
Sherrondria Buchanan
Keyword(s):  
Comparative Studies ◽  
Size Range ◽  
Brain Size ◽  
Brain Evolution ◽  
Processing Capacity ◽  
Primate Brain ◽  
Complex Organization ◽  
Architectural Principles ◽  
The Brain ◽  
Organizing Principles

Comparative studies of the brain in vertebrates suggest that there are general architectural principles leading to its development and overall improvement. We are beginning to understand the geometric, biophysical and energy constraints that have contributed to the progression and practical organization of the brain. The object of this review is to present current perspectives on primate brain evolution, and to examine some hypothetical organizing principles that underlie the brain's complex organization. It is shown that the development of the cortex coordinates folding with connectivity in a way that produces smaller and faster brains. It will be discussed that at a brain size of about 3500 cm3, equivalent to a brain that is two to three times larger than the modern man, the brain seems to reach its maximum processing capacity. As the brain grows larger than this particular size range, it becomes less proficient it will ultimately restrict any improvement and overall function.

scholarly journals Rethinking the Effects of Body Size on the Study of Brain Size Evolution

2019 ◽  
Vol 93 (4) ◽  
pp. 182-195 ◽  
Author(s):  
Enrique Font ◽  
Roberto García-Roa ◽  
Daniel Pincheira-Donoso ◽  
Pau Carazo
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Size Variation ◽  
Brain Evolution ◽  
Scaling Effects ◽  
Selection Pressures ◽  
Body Tissues ◽  
Relative Brain Size ◽  
Functional Components ◽  
The Brain

Body size correlates with most structural and functional components of an organism’s phenotype – brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. We address these problems by comparing brain-body relationships from across >1,000 species of birds and non-avian reptiles. Relative brain size in birds is often assumed to be 10 times larger than in reptiles of similar body size. We examine how differences in the specific gravity of body tissues and in body design (e.g., presence/absence of a tail or a dense shell) between these two groups can affect estimates of relative brain size. Using phylogenetic comparative analyses, we show that the gap in relative brain size between birds and reptiles has been grossly exaggerated. Our results highlight the need to take into account differences between taxa arising from selection pressures affecting body size and design, and call into question the widespread misconception that reptile brains are small and incapable of supporting sophisticated behavior and cognition.

Regional selection of the brain size regulating gene CASC5 provides new insight into human brain evolution

2016 ◽  
Vol 136 (2) ◽  
pp. 193-204 ◽  
Author(s):  
Lei Shi ◽  
Enzhi Hu ◽  
Zhenbo Wang ◽  
Jiewei Liu ◽  
Jin Li ◽  
...  
Keyword(s):  
Human Brain ◽  
Brain Size ◽  
Brain Evolution ◽  
Human Brain Evolution ◽  
The Brain ◽  
Insight Into ◽  
Selection Of

Brain evolution in Homo: The “radiator” theory

1990 ◽  
Vol 13 (2) ◽  
pp. 333-344 ◽  
Author(s):  
Dean Falk
Keyword(s):  
Jugular Vein ◽  
Brain Size ◽  
Brain Evolution ◽  
Hominid Evolution ◽  
The Other ◽  
Early Hominids ◽  
Emissary Veins ◽  
Intense Solar Radiation ◽  
The Brain ◽  
Mosaic Habitats

AbstractThe “radiator” theory of brain evolution is proposed to account for “mosaic evolution” whereby brain size began to increase rapidly in the genus Homo well over a million years after bipedalism had been selected for in early hominids. Because hydrostatic pressures differ across columns of fluid depending on orientation (posture), vascular systems of early bipeds became reoriented so that cranial blood flowed preferentially to the vertebral plexus instead of the internal jugular vein in response to gravity. The Hadar early hominids and robust australopithecines partly achieved this reorientation with a dramatically enlarged occipital/marginal sinus system. On the other hand, hominids in the gracile australopithecine through Homo lineage delivered blood to the vertebral plexus via a widespread network of veins that became more elaborate through time. Mastoid and parietal emissary veins are representatives of this network, and increases in their frequencies during hominid evolution are indicative of its development. Brain size increased with increased frequencies of mastoid and parietal emissary veins in the lineage leading to and including Homo, but remained conservative in the robust australopithecine lineage that lacked the network of veins. The brain is an extremely heatsensitive organ and emissary veins in humans have been shown to cool the brain under conditions of hyperthermia. Thus, the network of veins in the lineage leading to Homo acted as a radiator that released a thermal constraint on brain size. The radiator theory is in keeping with the belief that basal gracile and basal robust australopithecines occupied distinct niches, with the former living in savanna mosaic habitats that were subject to hot temperatures and intense solar radiation during the day.

scholarly journals Understanding primate brain evolution

2007 ◽  
Vol 362 (1480) ◽  
pp. 649-658 ◽  
Author(s):  
R.I.M Dunbar ◽  
Susanne Shultz
Keyword(s):  
Life History ◽  
Path Analysis ◽  
Group Size ◽  
Brain Size ◽  
Brain Evolution ◽  
Primate Brain ◽  
The Social ◽  
Large Brain ◽  
Brain Data ◽  
The Relationship

We present a detailed reanalysis of the comparative brain data for primates, and develop a model using path analysis that seeks to present the coevolution of primate brain (neocortex) and sociality within a broader ecological and life-history framework. We show that body size, basal metabolic rate and life history act as constraints on brain evolution and through this influence the coevolution of neocortex size and group size. However, they do not determine either of these variables, which appear to be locked in a tight coevolutionary system. We show that, within primates, this relationship is specific to the neocortex. Nonetheless, there are important constraints on brain evolution; we use path analysis to show that, in order to evolve a large neocortex, a species must first evolve a large brain to support that neocortex and this in turn requires adjustments in diet (to provide the energy needed) and life history (to allow sufficient time both for brain growth and for ‘software’ programming). We review a wider literature demonstrating a tight coevolutionary relationship between brain size and sociality in a range of mammalian taxa, but emphasize that the social brain hypothesis is not about the relationship between brain/neocortex size and group size per se ; rather, it is about social complexity and we adduce evidence to support this. Finally, we consider the wider issue of how mammalian (and primate) brains evolve in order to localize the social effects.

scholarly journals Functional divergence of the brain-size regulating gene MCPH1 during primate evolution and the origin of humans

BMC Biology ◽  
2013 ◽  
Vol 11 (1) ◽  
pp. 62 ◽  
Author(s):  
Lei Shi ◽  
Ming Li ◽  
Qiang Lin ◽  
Xuebin Qi ◽  
Bing Su
Keyword(s):  
Brain Size ◽  
Functional Divergence ◽  
Primate Evolution ◽  
The Brain

scholarly journals The impact of locomotion on the brain evolution of squirrels and close relatives

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Ornella C. Bertrand ◽  
Hans P. Püschel ◽  
Julia A. Schwab ◽  
Mary T. Silcox ◽  
Stephen L. Brusatte
Keyword(s):  
Body Mass ◽  
Brain Size ◽  
Brain Evolution ◽  
Olfactory Bulbs ◽  
Component Size ◽  
Highly Correlated ◽  
Close Relatives ◽  
The Impact ◽  
The Brain ◽  
Opposing Effect

AbstractHow do brain size and proportions relate to ecology and evolutionary history? Here, we use virtual endocasts from 38 extinct and extant rodent species spanning 50+ million years of evolution to assess the impact of locomotion, body mass, and phylogeny on the size of the brain, olfactory bulbs, petrosal lobules, and neocortex. We find that body mass and phylogeny are highly correlated with relative brain and brain component size, and that locomotion strongly influences brain, petrosal lobule, and neocortical sizes. Notably, species living in trees have greater relative overall brain, petrosal lobule, and neocortical sizes compared to other locomotor categories, especially fossorial taxa. Across millions of years of Eocene-Recent environmental change, arboreality played a major role in the early evolution of squirrels and closely related aplodontiids, promoting the expansion of the neocortex and petrosal lobules. Fossoriality in aplodontiids had an opposing effect by reducing the need for large brains.

scholarly journals Comparative brain analysis of wild and hatchery reared Mahseer (Tor putitora) relative to their body weight and length

2022 ◽  
Vol 82 ◽  
Author(s):  
N. Ullah ◽  
I. Ullah ◽  
M. Israr ◽  
A. Rasool ◽  
F. Akbar ◽  
...  
Keyword(s):  
Body Weight ◽  
Brain Size ◽  
Function Analysis ◽  
Analysis Of Covariance ◽  
Brain Morphology ◽  
Wild Stock ◽  
Significant Difference ◽  
Tor Putitora ◽  
Discriminate Function Analysis ◽  
The Brain

Abstract The present study was aimed at comparing the brain size of mahseer (Tor putitora) in relation to their body weight and standard length, to investigate the potential impact of rearing environment on brain development in fish. The weight of the brain and three of its subdivisions cerebellum (CB), optic tectum (OT), and telencephalon (TC) were measured for both wild and hatchery-reared fish. The data was analysed using multiple analysis of covariance (MANCOVA), analysis of covariance (ANCOVA), and discriminate function analysis (DFA). We found the fish reared under hatchery conditions exhibit smaller brain size related to body weight, when compared to the wild ones. A significant (p<0.5) difference was observed in the length of CB and OT concerning the standard body length while no significant difference was found in TC of the fish from both the origins. The results of the current study highlight a logical assumption that neural deficiency affects the behaviour of fish, that’s why the captive-reared fish show maladaptive response and face fitness decline when released to the natural environment for wild stock enhancement. The current study concluded that hatchery-reared fish exhibit variations in gross brain morphology as compared to their wild counterpart.

scholarly journals Revisiting the social brain hypothesis: contest duration depends on loser’s brain size

2018 ◽  
Author(s):  
Wouter van der Bijl ◽  
Séverine D. Buechel ◽  
Alexander Kotrschal ◽  
Niclas Kolm
Keyword(s):  
Social Competence ◽  
Cognitive Ability ◽  
Brain Size ◽  
Empirical Support ◽  
Group Living ◽  
Brain Morphology ◽  
Selection Line ◽  
Behavioral Mechanism ◽  
The Social ◽  
The Brain

AbstractBackgroundBrain size is expected to evolve by a balance between cognitive benefits and energetic costs. Several influential hypotheses have suggested that large brains may be especially beneficial in social contexts. Group living and competition may pose unique cognitive challenges to individuals and favor the evolution of increased cognitive ability. Evidence comes from comparative studies on the link between social complexity and brain morphology, but the strength of empirical support has recently been challenged. In addition, the behavioral mechanisms that would link cognitive ability to sociality are rarely studied. Here we take an alternative approach and investigate experimentally how brain size can relate to the social competence of individuals within species, a problem that so far has remained unresolved. We use the unique guppy brain size selection line model system to evaluate whether large brains are advantageous by allowing individuals to better assess their performance in a social contest situation. Based on theoretical literature, we predict that contest duration should depend on the brain size of the loser, as it is the capitulation of the losing individual that ends the fight.ResultsFirst, we show that studying the movement of competitors during contests allows for precise estimation of the dominance timeline in guppies, even when overt aggression is typically one-sided and delayed. Second, we staged contests between pairs of male that had been artificially selected for large and small relative brain size, with demonstrated differences in cognitive ability. We show that dominance was established much earlier in contests with large-brained losers, whereas the brain size of the winner had no effect. Following our prediction, large-brained individuals gave up more quickly when they were going to lose.ConclusionsThese results suggest that large-brained individuals assess their performance in contests better and that social competence indeed can depend on brain size. Conflict resolution may therefore be an important behavioral mechanism behind macro-evolutionary patterns between sociality and brain size. Since conflict is ubiquitous among group-living animals, the possible effects of the social environment on the evolution of cognition may be more broadly applicable than previously thought.

scholarly journals The evolution of brain size among the Homininae and selection at ASPM and MCPH1 genes

2021 ◽  
Vol 2 (2) ◽  
pp. 293-310
Author(s):  
Sandra Leyva-Hernández ◽  
Ricardo Fong-Zazueta ◽  
Luis Medrano-González ◽  
Ana Julia Aguirre-Samudio
Keyword(s):  
Positive Selection ◽  
Nucleotide Substitution ◽  
Brain Size ◽  
Phylogenetic Analyses ◽  
Evolutionary Relationship ◽  
Brain Evolution ◽  
Haplotype Blocks ◽  
Accelerated Evolution ◽  
Relationship Of ◽  
The Brain

We examined the evolutionary relationship of the ASPM (abnormal spindle-like microcephaly associated) and MCPH1 (microcephalin-1) genes with brain volume among humans and other primates. We obtained sequences of these genes from 14 simiiform species including hominins. Two phylogenetic analyses of ASPM exon 3 and MCPH1 exons 8 and 11 were performed to maximize taxon sampling or sequence extension to compare the nucleotide substitution and encephalization rates, and examine signals of selection. Further assessment of selection among humans was done through the analysis of non-synonymous and synonymous substitutions (dN/dS), and linkage disequilibrium (LD) patterns. We found that the accelerated evolution of brain size in hominids, is related to synchronic acceleration in the substitution rates of ASPM and MCPH1, and to signals of positive selection, especially in hominins. The dN/dS and LD analyses in Homo detected sites under positive selection and some regions with haplotype blocks at several candidate sites surrounded by blocks in LD-equilibrium. Accelerations and signals of positive selection in ASPM and MCPH1 occurred in different lineages and periods being ASPM more closely related with the brain evolution of hominins. MCPH1 evolved under positive selection in different lineages of the Catarrhini, suggesting independent evolutionary roles of this gene among primates.

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