The domesticated brain: genetics of brain mass and brain structure in an avian species

Henriksen, Rie; Johnsson, Martin; Andersson, Leif; Jensen, Per; Wright, I. A.

doi:10.1038/srep34031

Cited by 54 publications

(112 citation statements)

References 61 publications

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“…The specific function of the cerebellum is not understood in all details, and recent research suggests that it may be more involved in social behaviour than what has previously been known (Barton, 2012). The varying selection effects on different brain regions is consistent with recent studies showing that the sizes of different parts of the brain are under genetic control of different loci (Henriksen et al, 2016).…”

Section: Size Of Brain and Other Organssupporting

confidence: 74%

Is evolution of domestication driven by tameness? A selective review with focus on chickens

Agnvall

Bélteky

Katajamaa

et al. 2018

Applied Animal Behaviour Science

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Domestication of animals offers unique possibilities to study evolutionary changes caused by similar selection pressures across a range of species. Animals from separate genera tend to develop a suite of phenotypic alterations referred to as "the domesticated phenotype". This involves changes in appearance, including loss of pigmentation, and alterations in body size and proportions. Furthermore, effects on reproduction and behaviour are typical. It is hypothesized that this recurring phenotype may be secondary effects of the increased tameness that is an inevitable first step in the domestication of any species. We first provide a general overview of observations and experiments from different species and then review in more detail a project attempting to recreate the initial domestication of chickens. Starting from an outbred population of Red Junglefowl, ancestors of all modern chickens, divergent lines were selected based on scores in a standardized fear-of-human test applied to all birds at 12 weeks of age. Up to the eighth selected generation, observations have been made on correlated effects of this selection on various phenotypes. The fear score had a significant heritability and was genetically correlated to several other behavioural traits. Furthermore, low-fear birds were larger at hatch, grew faster, laid larger eggs, had a modified metabolism and increased feed efficiency, had modified social behaviour and reduced brain size. Selection affected gene expression and DNAmethylation in the brains, but the genetic and epigenetic effects were not specifically associated with stress pathways. Further research should be focused on unraveling the genetic and epigenetic mechanisms underlying the correlated side-effects of reduced fear of humans.

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Section: Size Of Brain and Other Organssupporting

confidence: 74%

Is evolution of domestication driven by tameness? A selective review with focus on chickens

Agnvall

Bélteky

Katajamaa

et al. 2018

Applied Animal Behaviour Science

View full text Add to dashboard Cite

show abstract

“…Overall volume and neuron number of individual sub-components may also have independent genetic bases [47,48], implying that developmental models tying one to the other will have limited predictive power. Evidence for genetic independence between brain components has also been reported in sticklebacks and between chicken breeds [49,50]. In sticklebacks, genetic correlations between brain components are significantly less than unity, despite a relatively high correlation between brain and body size [49].…”

Section: (A) Selective Decoupling Of Coevolving Traitsmentioning

confidence: 77%

Brain evolution and development: adaptation, allometry and constraint

2016

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Phenotypic traits are products of two processes: evolution and development. But how do these processes combine to produce integrated phenotypes? Comparative studies identify consistent patterns of covariation, or allometries, between brain and body size, and between brain components, indicating the presence of significant constraints limiting independent evolution of separate parts. These constraints are poorly understood, but in principle could be either developmental or functional. The developmental constraints hypothesis suggests that individual components (brain and body size, or individual brain components) tend to evolve together because natural selection operates on relatively simple developmental mechanisms that affect the growth of all parts in a concerted manner. The functional constraints hypothesis suggests that correlated change reflects the action of selection on distributed functional systems connecting the different sub-components, predicting more complex patterns of mosaic change at the level of the functional systems and more complex genetic and developmental mechanisms. These hypotheses are not mutually exclusive but make different predictions. We review recent genetic and neurodevelopmental evidence, concluding that functional rather than developmental constraints are the main cause of the observed patterns. How brains evolve: the importance of scaling relationshipsThe components of any adaptive complex by definition undergo coordinated evolution. Brains, bodies and individual brain components therefore exhibit distinctive patterns of correlated evolution. But what do these patterns tell us about the roles of adaptation and constraint in shaping phenotypes? In particular, how and to what extent do constraints imposed by shared developmental programmes dictate allometric relationships between components, limiting their response to selection? These questions have shaped two key debates central to how we view brain evolution: the functional relevance of brain size and the adaptive potential of brain structure [1][2][3]. These debates hinge on whether observed patterns of scaling relationships, between brain and body size or different brain components, are the product of selection to maintain functional correspondence or constraints imposed by shared developmental programmes. Crucially, however, a sound understanding of the significance of scaling relationships in brain evolution has been limited by a lack of data on the genetic and developmental mechanisms that regulate brain size and structure. Here we discuss how recent discoveries about the genetic control of neural development shed new light on the issue.(a) Brain: body coevolution and the importance of size

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“…In recent years these predictions have been tested using quantitative genetics within a range of vertebrates, using wild pedigrees [Rogers et al, 2007[Rogers et al, , 2010Fears et al, 2009], inbred mouse strains [Hager et al, 2012] or divergent populations/domestic breeds [Henriksen et al, 2016;Noreikiene et al, 2015]. In support of the mosaic brain hypothesis, these have found little evidence for widespread genetic co-variation between major brain components.…”

Section: Discussionmentioning

confidence: 99%

Genetics of Cerebellar and Neocortical Expansion in Anthropoid Primates: A Comparative Approach

Harrison

Montgomery

2017

Brain Behav Evol

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What adaptive changes in brain structure and function underpin the evolution of increased cognitive performance in humans and our close relatives? Identifying the genetic basis of brain evolution has become a major tool in answering this question. Numerous cases of positive selection, altered gene expression or gene duplication have been identified that may contribute to the evolution of the neocortex, which is widely assumed to play a predominant role in cognitive evolution. However, the components of the neocortex co-evolve with other functionally interdependent regions of the brain, most notably in the cerebellum. The cerebellum is linked to a range of cognitive tasks and expanded rapidly during hominoid evolution. Here we present data that suggest that, across anthropoid primates, protein-coding genes with known roles in cerebellum development were just as likely to be targeted by selection as genes linked to cortical development. Indeed, based on currently available gene ontology data, protein-coding genes with known roles in cerebellum development are more likely to have evolved adaptively during hominoid evolution. This is consistent with phenotypic data suggesting an accelerated rate of cerebellar expansion in apes that is beyond that predicted from scaling with the neocortex in other primates. Finally, we present evidence that the strength of selection on specific genes is associated with variation in the volume of either the neocortex or the cerebellum, but not both. This result provides preliminary evidence that co-variation between these brain components during anthropoid evolution may be at least partly regulated by selection on independent loci, a conclusion that is consistent with recent intraspecific genetic analyses and a mosaic model of brain evolution that predicts adaptive evolution of brain structure.

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The domesticated brain: genetics of brain mass and brain structure in an avian species

Cited by 54 publications

References 61 publications

Is evolution of domestication driven by tameness? A selective review with focus on chickens

Is evolution of domestication driven by tameness? A selective review with focus on chickens

Brain evolution and development: adaptation, allometry and constraint

Genetics of Cerebellar and Neocortical Expansion in Anthropoid Primates: A Comparative Approach

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