Rapid Evolution of the Cerebellum in Humans and Other Great Apes

Abstract

. (2014) 'Rapid evolution of the cerebellum in humans and other great apes. ', Current biology., 24 (20). pp. 2440-2444. Further information on publisher's website:http://dx.doi.org/10. 1016/j.cub.2014.08.056 Publisher's copyright statement: NOTICE: this is the author's version of a work that was accepted for publication in Current Biology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reected in this document. Changes may have been made to this work since it was submitted for publication. A denitive version was subsequently published in Current Biology, 44, 20, 20 October 2014, 10.1016/j.cub.2014.056. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We apply a method for estimating branch--specific evolutionary rates on a phylogeny faster rate of cerebellar relative to neocortical evolution than found on the rest of the tree (βape=1.12, t=5.61, p<0.0001), and this remains true even when comparing ape branches only to those other branches showing a relative increase (βape=1.29, t=7.33, p<0.0001). Rates of cerebellar relative to cortical evolution were up to 6 times faster on ape compared to non--ape branches (Table 1).Increased relative cerebellar rates are apparent on the ancestral ape branch ( Figure 2 and Table 1), suggesting that the initial impetus may have been the demands of below--branch locomotion and arboreal route--planning in large--bodied primates, just as predicted by one theory of ape cognitive evolution [7]. Although Povinelli & Cant [8] argued that this adaptive shift occurred after the split between lesser and 5 great ape lineages, fossil evidence suggests that it predated the split [8], potentially providing the initial impetus for cerebellar expansion, with gibbons (Hylobates) then showing a distinct adaptive shift into a smaller--bodied true brachiation niche. It was during the radiation of the great ape clade, however, that cerebellar expansion became notably rapid. Whilst there was a slight but significant (1.5--fold) increase in the relative rate along the branches leading to all apes, the average relative rate increase along branches within the great ape clade was 3.2--fold, including a 3.6--fold increase on the branch leading to Homo ( Figure 2 and Table 1).If the acceleration we observe in cerebellar relative to neocortical rates across ape lineages reflects directional selection for enlargement, cerebellum size should be significantly larger relati...

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

“…Across primates, variation in cerebellum volume is linked to extractive foraging, after controlling for variation in neocortex volume [Barton, 2012]. The importance of the cerebellum in primate brain evolution is further bolstered by comparative analyses that demonstrate the cerebellum is expanded in hominoids [Rilling and Insel, 1998;MacLeod et al, 2003] due to a non-allometric expansion of the cerebellum relative to neocortex size that was caused by a faster-than-expected increase in cerebellum volume and neuron number that persisted throughout hominoid evolution [Barton and Venditti, 2014]. Although data at increasingly fine grained levels are more limited, the volumetric expansion of the whole cerebellum appears to be driven by a specific increase in the cerebellar lateral hemispheres [MacLeod et al, 2003] and possibly specific areas which receive direct functional connections with the prefrontal cortex [Balsters et al, 2010], an area of the neocortex long thought to be selectively expanded in hominoids [e.g., Semendeferi et al, 2001;Schoenemann et al, 2005;Sherwood et al, 2005;Smaers et al, 2011, but see Barton and Venditti, 2013;Gabi et al, 2016].…”

“…1 d). Again, given available GO data, these contrasting proportions suggest that the strength of positive selection acting on genes controlling cerebellum development may have increased during hominoid evolution, a clade in which the rate of cerebellar expansion significantly accelerated [Barton and Venditti, 2014] beyond the rate predicted based on scaling with the neocortex in other primates [Barton and Harvey, 2000;Barton and Venditti, 2013].…”

Conceptual and methodological issues in comparative neuroscience and psychology: a reassessment

“…For example, the neocortex has generally increased in size disproportionally compared to the other structures in primates, betraying selection on this structure. At the cellular level, the ratio of number of neurons in the cerebellum and neocortex remains almost constant (Herculano-Houzel 2010 see also Barton and Venditti 2014). This does not mean that the selection for these two structures has been of similar importance (since they have different patterns of connectivity), nor that these two structures have a comparable influence in the brain network.…”

Quantitative Study on Human Cerebellar Cortex from Anatomy Cadaver Preparations

“…This study was done in 12 adult human brains, regardless their sex. Other study showed that there are approximately 70 billion of neurons can be observed in the adult human cerebellum, with most of them reside at the granular layers (Barton & Venditti, 2014). These cells formed the cerebellar folia, which are vast in numbers depend on the learned sequential movement in one's daily life.…”