Primate brain size is predicted by diet but not sociality

DeCasien, Alex R.; Williams, Scott A.; Higham, James P.

doi:10.1038/s41559-017-0112

Cited by 347 publications

(372 citation statements)

References 73 publications

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“…Bear species, which do not exhibit dormancy and have a high caloric diet, showed a weak but significant correlation with bigger relative brain size. This would be in accordance with the trait-off between brain size and adipose tissue as well as studies on diet and brain size [60, 66–68]. The ecological shift towards a plant based diet alone did not affect encephalization in cave bears.…”

Section: Resultssupporting

confidence: 83%

The effect of body size evolution and ecology on encephalization in cave bears and extant relatives

Veitschegger

2017

BMC Evol Biol

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BackgroundThe evolution of larger brain volumes relative to body size in Mammalia is the subject of an extensive amount of research. Early on palaeontologists were interested in the brain of cave bears, Ursus spelaeus, and described its morphology and size. However, until now, it was not possible to compare the absolute or relative brain size in a phylogenetic context due to the lack of an established phylogeny, comparative material, and phylogenetic comparative methods. In recent years, many tools for comparing traits within phylogenies were developed and the phylogenetic position of cave bears was resolved based on nuclear as well as mtDNA.ResultsCave bears exhibit significantly lower encephalization compared to their contemporary relatives and intraspecific brain mass variation remained rather small. Encephalization was correlated with the combined dormancy-diet score. Body size evolution was a main driver in the degree of encephalization in cave bears as it increased in a much higher pace than brain size. In Ursus spelaeus, brain and body size increase over time albeit differently paced. This rate pattern is different in the highest encephalized bear species within the dataset, Ursus malayanus. The brain size in this species increased while body size heavily decreased compared to its ancestral stage.ConclusionsEarly on in the evolution of cave bears encephalization decreased making it one of the least encephalized bear species compared to extant and extinct members of Ursidae. The results give reason to suspect that as herbivorous animals, cave bears might have exhibited a physiological buffer strategy to survive the strong seasonality of their environment. Thus, brain size was probably affected by the negative trade-off with adipose tissue as well as diet. The decrease of relative brain size in the herbivorous Ursus spelaeus is the result of a considerable increase in body size possibly in combination with environmental conditions forcing them to rest during winters.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-017-0976-1) contains supplementary material, which is available to authorized users.

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Section: Resultssupporting

confidence: 83%

The effect of body size evolution and ecology on encephalization in cave bears and extant relatives

Veitschegger

2017

BMC Evol Biol

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“…29). Further, a recently published comparative analysis suggests that dietary factors, rather than sociality, are the primary drivers of increased relative brain size in primates (31). It remains to be seen whether these findings generalize to measures of neocortex volume, arguably more relevant to social intelligence (29,(55)(56)(57).…”

Section: Discussionmentioning

confidence: 99%

“…Across primates, support for multiple, nonexclusive hypotheses for enlarged brain (particularly neocortex) size has been identified in comparative studies, emphasizing the roles of social complexity (e.g., group size) (28,29), ecological intelligence (e.g., dietary complexity) (30,31), technical intelligence (e.g., tool use and technical innovation) (21,25,32), and behavioral complexity (e.g., innovativeness, social learning, and tactical deception) (21,25,33). Further, several comparative studies have found that larger brained primates have slower life histories, including longer juvenile periods and overall lifespans (e.g., ref.…”

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confidence: 99%

Coevolution of cultural intelligence, extended life history, sociality, and brain size in primates

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et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

168

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Explanations for primate brain expansion and the evolution of human cognition and culture remain contentious despite extensive research. While multiple comparative analyses have investigated variation in brain size across primate species, very few have addressed why primates vary in how much they use social learning. Here, we evaluate the hypothesis that the enhanced reliance on socially transmitted behavior observed in some primates has coevolved with enlarged brains, complex sociality, and extended lifespans. Using recently developed phylogenetic comparative methods we show that, across primate species, a measure of social learning proclivity increases with absolute and relative brain volume, longevity (specifically reproductive lifespan), and social group size, correcting for research effort. We also confirm relationships of absolute and relative brain volume with longevity (both juvenile period and reproductive lifespan) and social group size, although longevity is generally the stronger predictor. Relationships between social learning, brain volume, and longevity remain when controlling for maternal investment and are therefore not simply explained as a by-product of the generally slower life history expected for larger brained species. Our findings suggest that both brain expansion and high reliance on culturally transmitted behavior coevolved with sociality and extended lifespan in primates. This coevolution is consistent with the hypothesis that the evolution of large brains, sociality, and long lifespans has promoted reliance on culture, with reliance on culture in turn driving further increases in brain volume, cognitive abilities, and lifespans in some primate lineages. cultural evolution | social learning | brain evolution | primates | phylogenetic comparative analysis

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“…One possibility is that these sensitivities are related to evolutionary constraints, or to adaptive fitness benefits in other domains such as feeding advantages, with fitness benefits related to social signalling subsequently being involved in their maintenance. For example, frugivory is hypothesized to have played a key role in shaping primate cognitive and sensory evolution [51], and may have been an important initial selective pressure favouring primate trichromacy [3,27,29]. Further, our experiment does not distinguish between selection acting on the sensitivity of photoreceptors versus the predominant wavelengths of signals.…”

Section: Discussionmentioning

confidence: 99%

Experimental evidence that primate trichromacy is well suited for detecting primate social colour signals

et al. 2017

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Primate trichromatic colour vision has been hypothesized to be well tuned for detecting variation in facial coloration, which could be due to selection on either signal wavelengths or the sensitivities of the photoreceptors themselves. We provide one of the first empirical tests of this idea by asking whether, when compared with other visual systems, the information obtained through primate trichromatic vision confers an improved ability to detect the changes in facial colour that female macaque monkeys exhibit when they are proceptive. We presented pairs of digital images of faces of the same monkey to human observers and asked them to select the proceptive face. We tested images that simulated what would be seen by common catarrhine trichromatic vision, two additional trichromatic conditions and three dichromatic conditions. Performance under conditions of common catarrhine trichromacy, and trichromacy with narrowly separated LM cone pigments (common in female platyrrhines), was better than for evenly spaced trichromacy or for any of the dichromatic conditions. These results suggest that primate trichromatic colour vision confers excellent ability to detect meaningful variation in primate face colour. This is consistent with the hypothesis that social information detection has acted on either primate signal spectral reflectance or photoreceptor spectral tuning, or both.

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Primate brain size is predicted by diet but not sociality

Cited by 347 publications

References 73 publications

The effect of body size evolution and ecology on encephalization in cave bears and extant relatives

The effect of body size evolution and ecology on encephalization in cave bears and extant relatives

Coevolution of cultural intelligence, extended life history, sociality, and brain size in primates

Experimental evidence that primate trichromacy is well suited for detecting primate social colour signals

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