The Evolutions of Large Brain Size in Mammals: The ‘Over-700-Gram Club Quartet'

2013 ◽  
Vol 82 (1) ◽  
pp. 68-78 ◽  
Author(s):  
Paul R. Manger ◽  
Muhammad A. Spocter ◽  
Nina Patzke
Keyword(s):  
Brain Size ◽  
Large Brain

Brain size evolution in small mammals: test of the expensive tissue hypothesis

Mammalia ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ying Jiang ◽  
Jia Yu Wang ◽  
Xiao Fu Huang ◽  
Chun Lan Mai ◽  
Wen Bo Liao
Keyword(s):  
Small Mammals ◽  
Brain Size ◽  
Reproductive Investment ◽  
Generalized Least Squares ◽  
Offspring Number ◽  
Size Evolution ◽  
Large Brain ◽  
Species Evolution ◽  
The Cost ◽  
Expensive Tissue Hypothesis

Abstract Brain size exhibits significant changes within and between species. Evolution of large brains can be explained by the need to improve cognitive ability for processing more information in changing environments. However, brains are among the most energetically expensive organs. Enlarged brains can impose energetic demands that limit brain size evolution. The expensive tissue hypothesis (ETH) states that a decrease in the size of another expensive tissue, such as the gut, should compensate for the cost of a large brain. We studied the interplay between energetic limitations and brain size evolution in small mammals using phylogenetically generalized least squares (PGLS) regression analysis. Brain mass was not correlated with the length of the digestive tract in 37 species of small mammals after correcting for phylogenetic relationships and body size effects. We further found that the evolution of a large brain was not accompanied by a decrease in male reproductive investments into testes mass and in female reproductive investment into offspring number. The evolution of brain size in small mammals is inconsistent with the prediction of the ETH.

scholarly journals Why are there so few smart mammals (but so many smart birds)?

2008 ◽  
Vol 5 (1) ◽  
pp. 125-129 ◽  
Author(s):  
Karin Isler ◽  
Carel P Van Schaik
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Population Increase ◽  
Large Brain ◽  
Cooperatively Breeding ◽  
Steep Decline ◽  
Relative Brain Size ◽  
Altricial Birds ◽  
Rates Of Growth ◽  
Very High

The expensive brain hypothesis predicts an interspecific link between relative brain size and life-history pace. Indeed, animals with relatively large brains have reduced rates of growth and reproduction. However, they also have increased total lifespan. Here we show that the reduction in production with increasing brain size is not fully compensated by the increase in lifespan. Consequently, the maximum rate of population increase ( r max ) is negatively correlated with brain mass. This result is not due to a confounding effect of body size, indicating that the well-known correlation between r max and body size is driven by brain size, at least among homeothermic vertebrates. Thus, each lineage faces a ‘grey ceiling’, i.e. a maximum viable brain size, beyond which r max is so low that the risk of local or species extinction is very high. We found that the steep decline in r max with brain size is absent in taxa with allomaternal offspring provisioning, such as cooperatively breeding mammals and most altricial birds. These taxa thus do not face a lineage-specific grey ceiling, which explains the far greater number of independent origins of large brain size in birds than mammals. We also predict that (absolute and relative) brain size is an important predictor of macroevolutionary extinction patterns.

scholarly journals Brain enlargement and dental reduction were not linked in hominin evolution

2017 ◽  
Vol 114 (3) ◽  
pp. 468-473 ◽  
Author(s):  
Aida Gómez-Robles ◽  
Jeroen B. Smaers ◽  
Ralph L. Holloway ◽  
P. David Polly ◽  
Bernard A. Wood
Keyword(s):  
Brain Size ◽  
Behavioral Changes ◽  
Modern Humans ◽  
Distinctive Features ◽  
Hominin Evolution ◽  
Large Brain ◽  
Dental Reduction ◽  
Selection For ◽  
Brain Reorganization ◽  
Evolutionary Simulations

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

scholarly journals Selection for brain size impairs innate, but not adaptive immune responses

2016 ◽  
Vol 283 (1826) ◽  
pp. 20152857 ◽  
Author(s):  
Alexander Kotrschal ◽  
Niclas Kolm ◽  
Dustin J. Penn
Keyword(s):  
Immune Responses ◽  
Poecilia Reticulata ◽  
Brain Size ◽  
Innate Immune Responses ◽  
Rejection Reaction ◽  
Trade Off ◽  
Large Brain ◽  
Rejection Response ◽  
Selection For ◽  
Acquired Immune Responses

Both the brain and the immune system are energetically demanding organs, and when natural selection favours increased investment into one, then the size or performance of the other should be reduced. While comparative analyses have attempted to test this potential evolutionary trade-off, the results remain inconclusive. To test this hypothesis, we compared the tissue graft rejection (an assay for measuring innate and acquired immune responses) in guppies ( Poecilia reticulata ) artificially selected for large and small relative brain size. Individual scales were transplanted between pairs of fish, creating reciprocal allografts, and the rejection reaction was scored over 8 days (before acquired immunity develops). Acquired immune responses were tested two weeks later, when the same pairs of fish received a second set of allografts and were scored again. Compared with large-brained animals, small-brained animals of both sexes mounted a significantly stronger rejection response to the first allograft. The rejection response to the second set of allografts did not differ between large- and small-brained fish. Our results show that selection for large brain size reduced innate immune responses to an allograft, which supports the hypothesis that there is a selective trade-off between investing into brain size and innate immunity.

scholarly journals High-throughput whole-brain mapping of rhesus monkey at micron resolution

2020 ◽  
Author(s):  
Fang Xu ◽  
Yan Shen ◽  
Lufeng Ding ◽  
Chao-Yu Yang ◽  
Heng Tan ◽  
...  
Keyword(s):  
Rhesus Monkey ◽  
Large Scale ◽  
High Efficiency ◽  
Brain Size ◽  
Integrative Approach ◽  
Whole Brain ◽  
3 Dimensional ◽  
Large Brain ◽  
Thalamocortical Projections ◽  
Distinct Features

AbstractWhole-brain mesoscale mapping of primates has been hindered by large brain size and the relatively low throughput of available microscopy methods. Here, we present an integrative approach that combines primate-optimized tissue sectioning and clearing with ultrahigh-speed, large-scale, volumetric fluorescence microscopy, capable of completing whole-brain imaging of a rhesus monkey at 1 µm × 1 µm × 2.5 µm voxel resolution within 100 hours. A progressive strategy is developed for high-efficiency, long-range tracing of individual axonal fibers through the dataset of hundreds of terabytes, establishing a “Serial sectioning and clearing, 3-dimensional Microscopy, with semi-Automated Reconstruction and Tracing” (SMART) pipeline. This system supports effective connectome-scale mapping of large primates that reveals distinct features of thalamocortical projections of the rhesus monkey brain at the level of individual axonal fibers.

scholarly journals Interspecies Avian Brain Chimeras Reveal That Large Brain Size Differences Are Influenced by Cell–Interdependent Processes

PLoS ONE ◽  
2012 ◽  
Vol 7 (7) ◽  
pp. e42477 ◽  
Author(s):  
Chun-Chun Chen ◽  
Evan Balaban ◽  
Erich D. Jarvis
Keyword(s):  
Brain Size ◽  
Avian Brain ◽  
Large Brain

Do primates flexibly use spatio-temporal cues when foraging?

2020 ◽  
pp. 174702182097072
Author(s):  
Cinzia Trapanese ◽  
Hélène Meunier ◽  
Shelly Masi
Keyword(s):  
Brain Size ◽  
Seasonal Pattern ◽  
Temporal Distribution ◽  
Primate Species ◽  
Temporal Cues ◽  
Large Brain ◽  
Sapajus Apella ◽  
Average Proportion ◽  
Spatio Temporal ◽  
Free Ranging

Foraging in seasonal environments can be cognitively demanding. Comparative studies have associated large brain size with a frugivorous diet. We investigated the ability of three semi-free-ranging primate species with different degrees of frugivory ( Ntrials: Macaca tonkeana = 419, Macaca fascicularis = 197, Sapajus apella = 346) in developing a mental representation of the spatio-temporal distribution of food using foraging experiments. Forty-two boxes were fixed on trees, and each week (“season”), some of them were filled with fruits which were either highly preferred, or less preferred. Spatial (geometrical panels) and temporal (peel skin of the available fruit) cues were present at each season to indicate where (food location), what (which food) was available, and when. To test the flexible use of the cues in primate foraging behaviour, we first removed the spatial and temporal cues one at a time, and then, we manipulated the “seasonal” order of the available fruit. We compared the foraging performances in the absence and the presence of the cues and during the usual and unusual seasonal order. The average proportion of baited boxes chosen by the subjects in presence of both cues was high (between 73% and 98%) for all species. The primates seemed to remember the spatio-temporal food availability (or used other cues) because no difference was found between trials with or without our spatial and temporal cues. When the usual seasonal pattern was changed, they flexibly adjusted the feeding choice by using the provided temporal cues. We discuss these results also in view of a possible experimental bias.

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.

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