Multiple routes to mammalian diversity

Venditti, Chris; Meade, Andrew; Pagel, Mark

doi:10.1038/nature10516

Cited by 287 publications

(424 citation statements)

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“…We apply a method for estimating branch--specific evolutionary rates on a phylogeny [3] to comparative neuro--volumetric data (see Supplemental Information for data and sources), allowing us to detect shifts in the rates of evolutionary size change in individual brain structures. In line with previous studies indicating a strong general pattern of correlated evolution between cerebellum and neocortex [4--6], rates of size change in these two structures are significantly associated (β=0.94, t=35.95, p<0.0001), and both increased on phylogenetic branches within the ape clade ( Figure 1 and ref [5]).…”

Section: Resultsmentioning

confidence: 99%

“…To determine the branch-wise rates of evolution separately for the cerebellum and neocortex, we used the Bayesian reversible-jump variable-rates model of trait evolution [33]. This model allows us to trace the evolutionary history of shifts in the rate and timing of evolution without specifying in advance where these events are located.…”

Section: Phylogenetic and Statistical Methodsmentioning

confidence: 99%

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Rapid Evolution of the Cerebellum in Humans and Other Great Apes

Barton¹,

Venditti²

2017

Current Biology

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. (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...

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Section: Resultsmentioning

confidence: 99%

Section: Phylogenetic and Statistical Methodsmentioning

confidence: 99%

Rapid Evolution of the Cerebellum in Humans and Other Great Apes

Barton¹,

Venditti²

2017

Current Biology

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“…Our variable rates model applies a PGLS model of trait evolution implemented in a Bayesian framework to analyze the evolution of the continuously varying traits on a phylogenetic tree (23). This model estimates the posterior densities of the instantaneous variance of change along the branches of a phylogeny (the "rate" parameter).…”

Section: Methodsmentioning

confidence: 99%

“…One scaling mechanisms modifies the instantaneous rate along a single branch, whereas the other modifies the rate in a whole monophyletic group or clade. Over billions of iterations this model records for each branch in the tree the probability that its rate has been changed and what its mean rate is (23). Further details are provided in SI Methods.…”

Section: Methodsmentioning

confidence: 99%

Human frontal lobes are not relatively large

Barton

Venditti

2013

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

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One of the most pervasive assumptions about human brain evolution is that it involved relative enlargement of the frontal lobes. We show that this assumption is without foundation. Analysis of five independent data sets using correctly scaled measures and phylogenetic methods reveals that the size of human frontal lobes, and of specific frontal regions, is as expected relative to the size of other brain structures. Recent claims for relative enlargement of human frontal white matter volume, and for relative enlargement shared by all great apes, seem to be mistaken. Furthermore, using a recently developed method for detecting shifts in evolutionary rates, we find that the rate of change in relative frontal cortex volume along the phylogenetic branch leading to humans was unremarkable and that other branches showed significantly faster rates of change. Although absolute and proportional frontal region size increased rapidly in humans, this change was tightly correlated with corresponding size increases in other areas and whole brain size, and with decreases in frontal neuron densities. The search for the neural basis of human cognitive uniqueness should therefore focus less on the frontal lobes in isolation and more on distributed neural networks.

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“…Previously, we have shown that rates of body size evolution in mammals routinely violate the assumption of homogeneity (19), but how these rate changes might be related to size itself has not been studied. If changes toward larger size in the mammals have consistently occurred at rates that differ from changes toward smaller size, then reconstructed ancestral states accounting for these rate differences may track more closely the observed fossil record.…”

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Adaptive evolution toward larger size in mammals

Baker

Meade

Pagel

et al. 2015

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

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The notion that large body size confers some intrinsic advantage to biological species has been debated for centuries. Using a phylogenetic statistical approach that allows the rate of body size evolution to vary across a phylogeny, we find a long-term directional bias toward increasing size in the mammals. This pattern holds separately in 10 of 11 orders for which sufficient data are available and arises from a tendency for accelerated rates of evolution to produce increases, but not decreases, in size. On a branch-bybranch basis, increases in body size have been more than twice as likely as decreases, yielding what amounts to millions and millions of years of rapid and repeated increases in size away from the small ancestral mammal. These results are the first evidence, to our knowledge, from extant species that are compatible with Cope's rule: the pattern of body size increase through time observed in the mammalian fossil record. We show that this pattern is unlikely to be explained by several nonadaptive mechanisms for increasing size and most likely represents repeated responses to new selective circumstances. By demonstrating that it is possible to uncover ancient evolutionary trends from a combination of a phylogeny and appropriate statistical models, we illustrate how data from extant species can complement paleontological accounts of evolutionary history, opening up new avenues of investigation for both. macroevolution | adaptive evolution | evolutionary trends | Cope's rule | ancestral state reconstruction T he idea that large size confers some intrinsic advantage has lingered in the psyche of biologists for centuries. Researchers have proposed that bigger body sizes can increase tolerance to environmental extremes (1), reduce mortality (2), and enhance predation success (3), among other advantages. In support of these conjectures, analyses from a range of different taxonomic groups demonstrate that larger individuals within populations have significantly enhanced survival, fecundity, and mating success (4, 5). If these advantages are general and have played out over long time scales, they could explain the existence of Cope's rule (6): a broad trend toward increasing size through time (4, 5, 7).Mammals evolved from a relatively small common ancestor over 165 Ma (8-10) and went on to form one of the largest and most successful vertebrate radiations in Earth's history. Mammals vary greatly in size, spanning almost eight orders of magnitude. This variation implies that some groups have experienced much greater evolutionary change in size from the ancestral form than others. Indeed, the mammalian fossil record provides the clearest evidence in support of Cope's rule over long evolutionary time scales (6,11,12).Despite the paleontological support, evidence for Cope's rule remains elusive from studies of extant data alone (13-15), including studies of the mammals (16). A possible reason for the discrepancy between paleontological and extant data might be that conventional comparative methods for studying tr...

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Multiple routes to mammalian diversity

Cited by 287 publications

References 22 publications

Rapid Evolution of the Cerebellum in Humans and Other Great Apes

Rapid Evolution of the Cerebellum in Humans and Other Great Apes

Human frontal lobes are not relatively large

Adaptive evolution toward larger size in mammals

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