Brain reorganization, not relative brain size, primarily characterizes anthropoid brain evolution

In the paper

“PC5 (7.7%) the paleocortex”

In the paper

“Principal component 1 (PC1) is dominated by variation in relative brain size and accounts for up to 25.8 per cent of overall variation in brain evolution (table 1).”

In the paper

“Phylogenetic mapping of PC2 scores and brain size shows that great apes stand out in their combined investment in both prefrontal white matter and absolute brain size, in that prefrontal white matter keeps track with a substantial increase in brain size, with humans at the extreme of this pattern (figure 1a).”

In the paper

“Considering that our sample includes brain size values spanning 40 orders of magnitude (32.8cc for the New World monkey Pithecia monachus and 39.7 for the Old World monkey Miopithecus talapoin compared with 1418.9cc for our sample of humans)”

In the paper

“The hippocampus–entorhinal formation does not indicate a clade-specific pattern in combination with an emphasis on absolute brain size (see electronic supplementary material, S2), but displays particular variation in lineages where brain size has decreased (figure 2).”

In the paper

“Phylogenetic mapping of PC6 and PC7 reveals opposite patterns of investment across species with a joint investment in the cortico-cerebellar system and absolute brain size separating the ape from the monkey radiation between 30 and 20 Ma (figure 1c).”

In the paper

“Specifically, great apes combine increased investment in the cortico-cerebellar system with a decreased investment in the descending motor pathway (see electronic supplementary material, S2).”

In the paper

“Great apes stand out in a joint emphasis on the prefronto-striatal formation and absolute brain size; a trend that is inferred to originate with the dawn of the ape radiation (figure 1b).”

In the paper

“a comparative correlation between absolute brain size and cognitive ability in non-human primates [8]”

What the sources say

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In the paper

“and predict various aspects of behavioural capacity across the animal kingdom [13–16]”

What the sources say

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In the paper

“between relative brain size and survival in novel environments in different orders across the animal kingdom [2,9,10]”

What the sources say

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In the paper

“there are three elements that are fundamental to our understanding of these two aspects of brain evolution that have not been established: (i) What is the relative importance of relative brain size and mosaic changes in explaining variation in brain evolution?”

In the paper

“previous work has demonstrated that the neural system adapts in both size-dependent and size-independent ways.”

In the paper

“(iii) What are the temporal origin, rate and process underlying evolutionary shifts in mosaic reorganization for individual branches of the primate tree of life?”

In the paper

“In primates, the evolution of brain size (both in terms of absolute size and relative to body size) shows complex patterns of change involving both increases and decreases along different branches of the primate phylogeny [6,7].”

What the sources say

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In the paper

“The overall size of the brain plays an important part in neural adaptation”

What the sources say

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In the paper

“(ii) Which mosaic changes contribute most to explaining diversity in brain organization across species?”

In the paper

“This (mosaic) variation has been shown to reflect anatomical connectivity patterns [11,12]”

What the sources say

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In the paper

“Although allometric approaches per se reveal useful information on brain structure evolution”

What the sources say

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In the paper

“as the absolute size of the brain increases, interacting neurons are located further apart and the brain is likely to become more modular in organization [5]”

What the sources say

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In the paper

“This brain structure is generally considered to provide ‘an infrastructure for synthesizing a diverse range of information that lays the foundation for the complex forms of behaviour observed in primates’ [49, p. 59].”

What the sources say

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In the paper

“Recent functional connectivity research evidenced the preferential distant connectivity of heteromodal association areas, with some regions in the prefrontal cortex (medial PFC) displaying both high local (evidencing modularity) and high distant (evidencing multimodality) functional connectivity [51].”

What the sources say

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In the paper

“Because olfactory bulb and medulla volume are considered to have experienced the least amount of change across anthropoid evolution, and brain size the most, this component can primarily be interpreted as reflecting changes in relative brain size.”

In the paper

“This approach hereby significantly increases the resolution of evolutionary inferences and allows for more detailed interpretations of the evolutionary history of particular biological traits.”

In the paper

“The method that underlies this approach [23] infers variable rates of evolution for all individual lineages without a priori parametrization and provides realistic trait value estimates for extinct species.”

What the sources say

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In the paper

“The prefrontal cortex is a multimodal structure involved in social cognition [44], moral judgements [45], clan mentality [46], introspection [47] as well as goal-directed and stimulus-driven attention [48].”

What the sources say

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In the paper

“Australopithecus afarensis is considered to be close to the ancestral node of chimpanzees and humans and has an estimated fossil brain size of 434cc [71]”

What the sources say

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In the paper

“suggesting that putative developmental regularities in the evolution of brain structures in primates [65,66] do not contribute markedly to explaining neural system diversity across species and/or are commonly offset by mosaic reorganization.”

What the sources say

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In the paper

“Symmetry of brain reorganization in the context of increases versus decreases in absolute brain size has not been extensively studied, but preliminary evidence from the Chiroptera suggests there is asymmetry in the link between brain reorganization and cognitive capacity due to the different ecological niches available to species with different overall sizes [59].”

What the sources say

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In the paper

“congruent with suggestions that both comprise different memory systems [53,54] involved in forms of learning in which stimulus-response associations or habits are incrementally and sequentially acquired (striatal) [55–57] and more cognitive or declarative memory (hippocampal) [53,58].”

What the sources say

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In the paper

“Oreopithecus is considered to be derived from the great apes stem lineage, after its divergence from the gibbon lineage, and has an estimated fossil brain size of 383cc [71,72]”

What the sources say

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In the paper

“Proconsul is most often considered to be derived from the ape stem lineage, after its divergence from the Old World monkey lineage, and has an estimated fossil brain size of 162cc [73]”

What the sources say

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In the paper

“Functionally, these two components can roughly be associated with the execution of motor actions and the acquisition of new complex motor sequences.”

In the paper

“further confirming our interpretation that this may be due to smaller primates being confronted with a more diverse array of physical environments placing particular pressure on basic motor execution (such as locomotion).”

In the paper

“Overall, our phylogenetic analysis infers that a clade-specific investment in particular brain formations (prefrontal white matter, prefronto-striatal and higher motor control) in combination with increased absolute brain size differentiates great apes (and humans) from other primates (figure 1).”