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.

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

Epilogue

2019 ◽  
pp. 184-188
Author(s):  
Elisabeth A. Murray ◽  
Steven P. Wise ◽  
Mary K. L. Baldwin ◽  
Kim S. Graham
Keyword(s):  
Brain Size ◽  
Brain Organization ◽  
Evolutionary Innovation ◽  
Entire Brain ◽  
Evolutionary Success ◽  
Relationship Of ◽  
The Relationship ◽  
The Brain

In the epilogue, a couple of kids befriend a shy stegosaurus; a different stegosaurus worries about the rise of mammals; and a tyrannosaurus presents a situation report. But mainly we consider reptilian brains, the relationship of brain size to intelligence, and the evolutionary success of mammals. Contrary to an internet meme, no one has a “reptilian” or “lizard” brain lurking within. Our entire brain is human. Regarding intelligence, brain organization matters as much as brain size and maybe more. Once dinosaurs became extinct, the mammals that supplanted them had much smaller brains than large dinosaurs had. Instead, the success of mammals depended on the emergence of the neocortex, a new part of the brain. Eventually, this evolutionary innovation came to dominate both the brain and the memories that it contains.

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 Mating system and brain size in bats

2005 ◽  
Vol 273 (1587) ◽  
pp. 719-724 ◽  
Author(s):  
Scott Pitnick ◽  
Kate E Jones ◽  
Gerald S Wilkinson
Keyword(s):  
Sexual Selection ◽  
Mating System ◽  
Multiple Mating ◽  
Brain Size ◽  
Evolutionary Relationship ◽  
Brain Evolution ◽  
Correlated Evolution ◽  
Mate Fidelity ◽  
Sexually Selected Traits ◽  
Selected Traits

The contribution of sexual selection to brain evolution has been little investigated. Through comparative analyses of bats, we show that multiple mating by males, in the absence of multiple mating by females, has no evolutionary impact on relative brain dimension. In contrast, bat species with promiscuous females have relatively smaller brains than do species with females exhibiting mate fidelity. This pattern may be a consequence of the demonstrated negative evolutionary relationship between investment in testes and investment in brains, both metabolically expensive tissues. These results have implications for understanding the correlated evolution of brains, behaviour and extravagant sexually selected traits.

Neocortical Anatomy in the South American Plains Vizcacha, Lagostomus maximus, Reveals Different Strategies in Encephalic Development among Hystricomorpha and Myomorpha Rodents

2021 ◽  
pp. 1-12
Author(s):  
Alejandro Raúl Schmidt ◽  
María Constanza Gariboldi ◽  
Santiago Andrés Cortasa ◽  
Sofía Proietto ◽  
María Clara Corso ◽  
...  
Keyword(s):  
Cortical Thickness ◽  
Brain Size ◽  
Phylogenetic Analyses ◽  
Inverse Correlation ◽  
Bilateral Symmetry ◽  
Mean Value ◽  
South American ◽  
Correlation Pattern ◽  
Lagostomus Maximus ◽  
The Brain

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 <i>Lagostomus maximus</i> 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.

scholarly journals The gastrin-releasing peptide/bombesin system revisited by a reverse-evolutionary study considering Xenopus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Asuka Hirooka ◽  
Mayuko Hamada ◽  
Daiki Fujiyama ◽  
Keiko Takanami ◽  
Yasuhisa Kobayashi ◽  
...  
Keyword(s):  
Evolutionary Relationship ◽  
Multiple Roles ◽  
Genetic Database ◽  
Gastrin Releasing Peptide ◽  
Bombina Bombina ◽  
History Of ◽  
Mammalian Counterpart ◽  
Relationship Of ◽  
Clawed Frog ◽  
The Brain

AbstractBombesin is a putative antibacterial peptide isolated from the skin of the frog, Bombina bombina. Two related (bombesin-like) peptides, gastrin-releasing peptide (GRP) and neuromedin B (NMB) have been found in mammals. The history of GRP/bombesin discovery has caused little attention to be paid to the evolutionary relationship of GRP/bombesin and their receptors in vertebrates. We have classified the peptides and their receptors from the phylogenetic viewpoint using a newly established genetic database and bioinformatics. Here we show, by using a clawed frog (Xenopus tropicalis), that GRP is not a mammalian counterpart of bombesin and also that, whereas the GRP system is widely conserved among vertebrates, the NMB/bombesin system has diversified in certain lineages, in particular in frog species. To understand the derivation of GRP system in the ancestor of mammals, we have focused on the GRP system in Xenopus. Gene expression analyses combined with immunohistochemistry and Western blotting experiments demonstrated that GRP peptides and their receptors are distributed in the brain and stomach of Xenopus. We conclude that GRP peptides and their receptors have evolved from ancestral (GRP-like peptide) homologues to play multiple roles in both the gut and the brain as one of the ‘gut-brain peptide’ systems.

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.

The Evolution of Intelligence

2018 ◽  
pp. 123-149
Author(s):  
Kevin N. Laland
Keyword(s):  
Social Learning ◽  
Brain Size ◽  
Brain Evolution ◽  
Human Mind ◽  
Feedback Mechanism ◽  
Eminent Scientist ◽  
Cultural Processes ◽  
The Brain ◽  
Size And Structure ◽  
Complex Organ

This chapter fleshes out the “cultural drive” hypothesis proposed by eminent scientist Allan Wilson. It first considers the question of exactly how social learning could drive brain evolution when some animals managed to copy with tiny brains. Greater specification of the feedback mechanism by which cultural processes fostered the evolution of cognition was required if the argument was to be compelling. Second, the chapter looks at how many variables (e.g., diet, social complexity, latitude) had been shown to be associated with brain size in primates. In order to evaluate the hypothesis that cultural processes had played a particularly central role in the evolution of the human mind, whether social learning was a genuine cause of brain evolution must first be established. Third, the chapter argues that talk of increases in “brain size” is rather simplistic. The brain is a complex organ with extensive substructure, and with particular features and circuitry known to be important to specific biological functions. How the brain had changed over evolutionary time, and whether the observed changes in size and structure were consistent with what the cultural drive hypothesis predicted, also had to be established.

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.

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