scholarly journals Different environmental variables predict body and brain size evolution in Homo

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Manuel Will ◽  
Mario Krapp ◽  
Jay T. Stock ◽  
Andrea Manica
Keyword(s):  
Environmental Factors ◽  
Cognitive Abilities ◽  
Net Primary Productivity ◽  
Brain Size ◽  
Environmental Influence ◽  
Size Variation ◽  
Evolutionary Pattern ◽  
Statistical Framework ◽  
Size Evolution ◽  
Major Predictor

AbstractIncreasing body and brain size constitutes a key macro-evolutionary pattern in the hominin lineage, yet the mechanisms behind these changes remain debated. Hypothesized drivers include environmental, demographic, social, dietary, and technological factors. Here we test the influence of environmental factors on the evolution of body and brain size in the genus Homo over the last one million years using a large fossil dataset combined with global paleoclimatic reconstructions and formalized hypotheses tested in a quantitative statistical framework. We identify temperature as a major predictor of body size variation within Homo, in accordance with Bergmann’s rule. In contrast, net primary productivity of environments and long-term variability in precipitation correlate with brain size but explain low amounts of the observed variation. These associations are likely due to an indirect environmental influence on cognitive abilities and extinction probabilities. Most environmental factors that we test do not correspond with body and brain size evolution, pointing towards complex scenarios which underlie the evolution of key biological characteristics in later Homo.

scholarly journals Genes underlying the evolution of tetrapod testes size

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Joanna Baker ◽  
Andrew Meade ◽  
Chris Venditti
Keyword(s):  
Candidate Genes ◽  
Biological Diversity ◽  
Brain Size ◽  
Size Variation ◽  
Phenotypic Change ◽  
Testis Size ◽  
Protein Coding ◽  
Size Evolution ◽  
Size Diversity ◽  
To Come

Abstract Background Testes vary widely in mass relative to body mass across species, but we know very little about which genes underlie and contribute to such variation. This is partly because evidence for which genes are implicated in testis size variation tends to come from investigations involving just one or a few species. Contemporary comparative phylogenetic methods provide an opportunity to test candidate genes for their role in phenotypic change at a macro-evolutionary scale—across species and over millions of years. Previous attempts to detect genotype-phenotype associations across species have been limited in that they can only detect where genes have driven directional selection (e.g. brain size increase). Results Here, we introduce an approach that uses rates of evolutionary change to overcome this limitation to test whether any of twelve candidate genes have driven testis size evolution across tetrapod vertebrates—regardless of directionality. We do this by seeking a relationship between the rates of genetic and phenotypic evolution. Our results reveal five genes (Alkbh5, Dmrtb1, Pld6, Nlrp3, Sp4) that each have played unique and complex roles in tetrapod testis size diversity. In all five genes, we find strong significant associations between the rate of protein-coding substitutions and the rate of testis size evolution. Such an association has never, to our knowledge, been tested before for any gene or phenotype. Conclusions We describe a new approach to tackle one of the most fundamental questions in biology: how do individual genes give rise to biological diversity? The ability to detect genotype-phenotype associations that have acted across species has the potential to build a picture of how natural selection has sculpted phenotypic change over millions of years.

scholarly journals Testing hypotheses of marsupial brain size variation using phylogenetic multiple imputations and a Bayesian comparative framework

2021 ◽  
Vol 288 (1947) ◽  
Author(s):  
Orlin S. Todorov ◽  
Simone P. Blomberg ◽  
Anjali Goswami ◽  
Karen Sears ◽  
Patrik Drhlík ◽  
...  
Keyword(s):  
Litter Size ◽  
Brain Size ◽  
Size Variation ◽  
Reproductive Traits ◽  
Mammalian Brain ◽  
Gestation Length ◽  
High Coverage ◽  
Ecological Predictors ◽  
Size Evolution ◽  
Relative Brain Size

Considerable controversy exists about which hypotheses and variables best explain mammalian brain size variation. We use a new, high-coverage dataset of marsupial brain and body sizes, and the first phylogenetically imputed full datasets of 16 predictor variables, to model the prevalent hypotheses explaining brain size evolution using phylogenetically corrected Bayesian generalized linear mixed-effects modelling. Despite this comprehensive analysis, litter size emerges as the only significant predictor. Marsupials differ from the more frequently studied placentals in displaying a much lower diversity of reproductive traits, which are known to interact extensively with many behavioural and ecological predictors of brain size. Our results therefore suggest that studies of relative brain size evolution in placental mammals may require targeted co-analysis or adjustment of reproductive parameters like litter size, weaning age or gestation length. This supports suggestions that significant associations between behavioural or ecological variables with relative brain size may be due to a confounding influence of the extensive reproductive diversity of placental mammals.

scholarly journals Acrobatic Courtship Display Coevolves with Brain Size in Manakins (Pipridae)

2015 ◽  
Vol 85 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Willow R. Lindsay ◽  
Justin T. Houck ◽  
Claire E. Giuliano ◽  
Lainy B. Day
Keyword(s):  
Sexual Selection ◽  
Cognitive Abilities ◽  
Brain Size ◽  
Brain Evolution ◽  
Neural Systems ◽  
Motor Behaviour ◽  
Size Evolution ◽  
Complex Motor ◽  
Display Behaviour ◽  
Selection For

Acrobatic display behaviour is sexually selected in manakins (Pipridae) and can place high demands on many neural systems. Manakin displays vary across species in terms of behavioural complexity, differing in number of unique motor elements, production of mechanical sounds, cooperation between displaying males, and construction of the display site. Historically, research emphasis has been placed on neurological specializations for vocal aspects of courtship, and less is known about the control of physical, non-vocal displays. By examining brain evolution in relation to extreme acrobatic feats such as manakin displays, we can vastly expand our knowledge of how sexual selection acts on motor behaviour. We tested the hypothesis that sexual selection for complex motor displays has selected for larger brains across the Pipridae. We found that display complexity positively predicts relative brain weight (adjusted for body size) after controlling for phylogeny in 12 manakin species and a closely related flycatcher. This evidence suggests that brain size has evolved in response to sexual selection to facilitate aspects of display such as motor, sensorimotor, perceptual, and cognitive abilities. We show, for the first time, that sexual selection for acrobatic motor behaviour can drive brain size evolution in avian species and, in particular, a family of suboscine birds.

scholarly journals Predator-driven brain size evolution in natural populations of Trinidadian killifish ( Rivulus hartii )

2016 ◽  
Vol 283 (1834) ◽  
pp. 20161075 ◽  
Author(s):  
Matthew R. Walsh ◽  
Whitnee Broyles ◽  
Shannon M. Beston ◽  
Stephan B. Munch
Keyword(s):  
Brain Size ◽  
Natural Populations ◽  
Size Variation ◽  
Laboratory Selection ◽  
Trade Offs ◽  
Female Brain ◽  
Size Evolution ◽  
Selection Experiments ◽  
Fitness Benefits ◽  
Recent Laboratory

Vertebrates exhibit extensive variation in relative brain size. It has long been assumed that this variation is the product of ecologically driven natural selection. Yet, despite more than 100 years of research, the ecological conditions that select for changes in brain size are unclear. Recent laboratory selection experiments showed that selection for larger brains is associated with increased survival in risky environments. Such results lead to the prediction that increased predation should favour increased brain size. Work on natural populations, however, foreshadows the opposite trajectory of evolution; increased predation favours increased boldness, slower learning, and may thereby select for a smaller brain. We tested the influence of predator-induced mortality on brain size evolution by quantifying brain size variation in a Trinidadian killifish, Rivulus hartii , from communities that differ in predation intensity. We observed strong genetic differences in male (but not female) brain size between fish communities; second generation laboratory-reared males from sites with predators exhibited smaller brains than Rivulus from sites in which they are the only fish present. Such trends oppose the results of recent laboratory selection experiments and are not explained by trade-offs with other components of fitness. Our results suggest that increased male brain size is favoured in less risky environments because of the fitness benefits associated with faster rates of learning and problem-solving behaviour.

scholarly journals Testing hypotheses of marsupial brain size variation using phylogenetic multiple imputations and a Bayesian comparative framework

2021 ◽  
Author(s):  
Orlin S. Todorov ◽  
Simone P. Blomberg ◽  
Anjali Goswami ◽  
Karen Sears ◽  
Patrik Drhlík ◽  
...  
Keyword(s):  
Litter Size ◽  
Brain Size ◽  
Size Variation ◽  
Reproductive Traits ◽  
Mammalian Brain ◽  
Gestation Length ◽  
High Coverage ◽  
Ecological Predictors ◽  
Size Evolution ◽  
Relative Brain Size

AbstractConsiderable controversy exists about which hypotheses and variables best explain mammalian brain size variation. We use a new, high-coverage dataset of marsupial brain and body sizes, and the first phylogenetically imputed full datasets of 16 predictor variables, to model the prevalent hypotheses explaining brain size evolution using phylogenetically corrected Bayesian generalised linear mixed-effects modelling. Despite this comprehensive analysis, litter size emerges as the only significant predictor. Marsupials differ from the more frequently studied placentals in displaying much lower diversity of reproductive traits, which are known to interact extensively with many behavioural and ecological predictors of brain size. Our results therefore suggest that studies of relative brain size evolution in placental mammals may require targeted co-analysis or adjustment of reproductive parameters like litter size, weaning age, or gestation length. This supports suggestions that significant associations between behavioural or ecological variables with relative brain size may be due to a confounding influence of the extensive reproductive diversity of placental mammals.

scholarly journals Metabolic costs of brain size evolution

2006 ◽  
Vol 2 (4) ◽  
pp. 557-560 ◽  
Author(s):  
Karin Isler ◽  
Carel P van Schaik
Keyword(s):  
Brain Size ◽  
Size Variation ◽  
Brain Evolution ◽  
Energy Costs ◽  
Main Interest ◽  
Ecological Benefits ◽  
Size Evolution ◽  
Large Brain ◽  
Metabolic Costs ◽  
Cognitive Benefits

Abstract In the ongoing discussion about brain evolution in vertebrates, the main interest has shifted from theories focusing on energy balance to theories proposing social or ecological benefits of enhanced intellect. With the availability of a wealth of new data on basal metabolic rate (BMR) and brain size and with the aid of reliable techniques of comparative analysis, we are able to show that in fact energetics is an issue in the maintenance of a relatively large brain, and that brain size is positively correlated with the BMR in mammals, controlling for body size effects. We conclude that attempts to explain brain size variation in different taxa must consider the ability to sustain the energy costs alongside cognitive benefits.

scholarly journals Dolphin social intelligence: complex alliance relationships in bottlenose dolphins and a consideration of selective environments for extreme brain size evolution in mammals

2007 ◽  
Vol 362 (1480) ◽  
pp. 587-602 ◽  
Author(s):  
Richard C Connor
Keyword(s):  
Cognitive Abilities ◽  
Social Intelligence ◽  
Brain Size ◽  
Bottlenose Dolphins ◽  
Sperm Whale ◽  
Shark Bay ◽  
External Threats ◽  
Size Evolution ◽  
Large Brain ◽  
Selection For

Bottlenose dolphins in Shark Bay, Australia, live in a large, unbounded society with a fission–fusion grouping pattern. Potential cognitive demands include the need to develop social strategies involving the recognition of a large number of individuals and their relationships with others. Patterns of alliance affiliation among males may be more complex than are currently known for any non-human, with individuals participating in 2–3 levels of shifting alliances. Males mediate alliance relationships with gentle contact behaviours such as petting, but synchrony also plays an important role in affiliative interactions. In general, selection for social intelligence in the context of shifting alliances will depend on the extent to which there are strategic options and risk. Extreme brain size evolution may have occurred more than once in the toothed whales, reaching peaks in the dolphin family and the sperm whale. All three ‘peaks’ of large brain size evolution in mammals (odontocetes, humans and elephants) shared a common selective environment: extreme mutual dependence based on external threats from predators or conspecific groups. In this context, social competition, and consequently selection for greater cognitive abilities and large brain size, was intense.

The Intelligent Brain

2021 ◽  
pp. 17-34
Author(s):  
Susan D. Healy
Keyword(s):  
Environmental Factors ◽  
Spatial Cognition ◽  
Cognitive Abilities ◽  
Brain Size ◽  
Food Storing ◽  
Definition Of

In this chapter I address the question as to why brain size and its variation is interesting. Because for many the answer is that a bigger brain endows greater intelligence, in this chapter I first provide a definition of intelligence, or cognition. I then describe a variety of factors that need to be considered in order to attempt to make comparisons, within or among species, of cognitive abilities. These include motivation, environmental factors, and methodologies used to train and test animals (typically) in the laboratory. For the remainder of the chapter I use the demonstration of the relationships between food storing, spatial cognition, and the hippocampus to illustrate these issues.

Brain size in Hylarana guentheri seems unaffected by variation in temperature and growth season

2017 ◽  
Vol 67 (3-4) ◽  
pp. 209-225 ◽  
Author(s):  
Jun Gu ◽  
Da Yong Li ◽  
Yi Luo ◽  
Song Bei Ying ◽  
Lan Ya Zhang ◽  
...  
Keyword(s):  
Brain Size ◽  
Behavioral Flexibility ◽  
Size Variation ◽  
Brain Regions ◽  
Growth Season ◽  
Food Scarcity ◽  
Size Evolution ◽  
Cognitive Benefits ◽  
Males And Females ◽  
Temperature And Growth

Brain size varies dramatically between vertebrate species. Two prominent adaptive hypotheses – the Cognitive Buffer Hypothesis (CBH) and the Expensive Brain Hypothesis (EBH) – have been proposed to explain brain size evolution. The CBH assumes that brain size should increase with seasonality, as the cognitive benefits of a larger brain should help overcoming periods of food scarcity via, for example, increased behavioral flexibility. Alternatively, the EBH states that brain size should decrease with seasonality because a smaller brain confers energetic benefits in periods of food scarcity. Here, to test the two adaptive hypotheses by studying the effects of variation in temperature and growth season on variations in overall brain size and the size of specific brain regions (viz. olfactory nerves, olfactory bulbs, telencephalon, optic tectum and cerebellum) among Hylarana guentheri populations. Inconsistent with the predictions of both the EBH and the CBH, variation in temperature and growth season did not exhibit correlations with overall brain size and the size of brain regions across populations. Hence, our data do not provide support for either the EBH or the CBH to explain brain size variation in H. guentheri. Furthermore, brain size variation did not differ between males and females in this species. Our findings suggest that both the variation in temperature and growth season did not shape the variation in brain size in H. guentheri.

scholarly journals The genetic regulation of size variation in the transcriptome of the cerebrum in the chicken and its role in domestication and brain size evolution

BMC Genomics ◽  
2020 ◽  
Vol 21 (1) ◽  
Author(s):  
Andrey Höglund ◽  
Katharina Strempfl ◽  
Jesper Fogelholm ◽  
Dominic Wright ◽  
Rie Henriksen
Keyword(s):  
Brain Size ◽  
Genetic Regulation ◽  
Size Variation ◽  
Size Evolution
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