5 research outputs found
Sociality does not drive the evolution of large brains in eusocial African mole-rats
The social brain hypothesis (SBH) posits that the demands imposed on individuals by living in cohesive
social groups exert a selection pressure favouring the evolution of large brains and complex cognitive
abilities. Using volumetry and the isotropic fractionator to determine the size of and numbers of
neurons in specific brain regions, here we test this hypothesis in African mole-rats (Bathyergidae).
These subterranean rodents exhibit a broad spectrum of social complexity, ranging from strictly solitary
through to eusocial cooperative breeders, but feature similar ecologies and life history traits. We found
no positive association between sociality and neuroanatomical correlates of information-processing
capacity. Solitary species are larger, tend to have greater absolute brain size and have more neurons
in the forebrain than social species. The neocortex ratio and neuronal counts correlate negatively with
social group size. These results are clearly inconsistent with the SBH and show that the challenges
coupled with sociality in this group of rodents do not require brain enlargement or fundamental
reorganization. These findings suggest that group living or pair bonding per se does not select strongly
for brain enlargement unless coupled with Machiavellian interactions affecting individual fitness.The Czech Science Foundation (14–2758 S, to P.N.), Grant Agency of Charles
University (325515, to K.K.) and the European Social Fund and the state budget of the Czech Republic
(CZ.1.07/2.3.00/30.0022, to S.O.).http://www.nature.com/srepam2018Mammal Research InstituteZoology and Entomolog
Brain size and neuron numbers drive differences in yawn duration across mammals and birds
Recent studies indicate that yawning evolved as a brain cooling mechanism. Given that larger brains have greater thermolytic needs and brain temperature is determined in part by heat production from neuronal activity, it was hypothesized that animals with larger brains and more neurons would yawn longer to produce comparable cooling effects. To test this, we performed the largest study on yawning ever conducted, analyzing 1291 yawns from 101 species (55 mammals; 46 birds). Phylogenetically controlled analyses revealed robust positive correlations between yawn duration and (1) brain mass, (2) total neuron number, and (3) cortical/pallial neuron number in both mammals and birds, which cannot be attributed solely to allometric scaling rules. These relationships were similar across clades, though mammals exhibited considerably longer yawns than birds of comparable brain and body mass. These findings provide further evidence suggesting that yawning is a thermoregulatory adaptation that has been conserved across amniote evolution
Brain size and neuron numbers drive differences in yawn duration across mammals and birds
Recent studies indicate that yawning evolved as a brain cooling mechanism. Given that larger brains have greater thermolytic needs and brain temperature is determined in part by heat production from neuronal activity, it was hypothesized that animals with larger brains and more neurons would yawn longer to produce comparable cooling effects. To test this, we performed the largest study on yawning ever conducted, analyzing 1291 yawns from 101 species (55 mammals; 46 birds). Phylogenetically controlled analyses revealed robust positive correlations between yawn duration and (1) brain mass, (2) total neuron number, and (3) cortical/pallial neuron number in both mammals and birds, which cannot be attributed solely to allometric scaling rules. These relationships were similar across clades, though mammals exhibited considerably longer yawns than birds of comparable brain and body mass. These findings provide further evidence suggesting that yawning is a thermoregulatory adaptation that has been conserved across amniote evolution
Brain size and neuron numbers drive differences in yawn duration across mammals and birds
Recent studies indicate that yawning evolved as a brain cooling mechanism. Given that larger brains have greater thermolytic needs and brain temperature is determined in part by heat production from neuronal activity, it was hypothesized that animals with larger brains and more neurons would yawn longer to produce comparable cooling effects. To test this, we performed the largest study on yawning ever conducted, analyzing 1291 yawns from 101 species (55 mammals; 46 birds). Phylogenetically controlled analyses revealed robust positive correlations between yawn duration and (1) brain mass, (2) total neuron number, and (3) cortical/pallial neuron number in both mammals and birds, which cannot be attributed solely to allometric scaling rules. These relationships were similar across clades, though mammals exhibited considerably longer yawns than birds of comparable brain and body mass. These findings provide further evidence suggesting that yawning is a thermoregulatory adaptation that has been conserved across amniote evolution