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Mosaic evolution of brain structure in mammals


The mammalian brain comprises a number of functionally distinct systems. It might therefore be expected that natural selection on particular behavioural capacities would have caused size changes selectively, in the systems mediating those capacities1,2,3. It has been claimed, however, that developmental constraints limited such mosaic evolution, causing co-ordinated size change among individual brain components3. Here we analyse comparative data to demonstrate that mosaic change has been an important factor in brain structure evolution. First, the neocortex shows about a fivefold difference in volume between primates and insectivores even after accounting for its scaling relationship with the rest of the brain. Second, brain structures with major anatomical and functional links evolved together independently of evolutionary change in other structures. This is true at the level of both basic brain subdivisions and more fine-grained functional systems. Hence, brain evolution in these groups involved complex relationships among individual brain components.

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Figure 1: Taxonomic differences in relative neocortex size among primates (strepsirhines and haplorhines) and insectivores.
Figure 2: Proportion of brain volume composed of neocortical grey matter in relation to overall brain volume.
Figure 3: Correlated evolution among major brain structures.
Figure 4: Correlated volumetric evolution of functionally related brain structures.


  1. Eisenberg, J. The Mammalian Radiations (University of Chicago, Chicago, 1981).

    Google Scholar 

  2. Harvey, P. H. & Krebs, J. R. Comparing brains. Science 249, 140–146 ( 1990).

    Article  ADS  CAS  Google Scholar 

  3. Finlay, B. L. & Darlington, R. B. Linked regularities in the development and evolution of mammalian brains. Science 268, 1578–1584 (1995).

    Article  ADS  CAS  Google Scholar 

  4. Innocenti, G. M. & Kaas, J. H. The cortex. Trends Neurosci. 18, 371–372 (1995).

    Article  CAS  Google Scholar 

  5. Kaas, J. H. The evolution of isocortex. Brain Behav. Evol. 46, 187–196 (1995).

    Article  CAS  Google Scholar 

  6. Dunbar, R. I. M. The social brain hypothesis. Evol. Anth. 6, 178–190 (1998).

    Article  Google Scholar 

  7. Finlay, B. L., Darlington, R. B. & Nicastro, N. Developmental structure in brain evolution. Behav. Brain Sci. (in the press).

  8. Hofman, M. A. On the evolution and geometry of the brain in mammals. Prog. Neurobiol. 32, 137–158 ( 1989).

    Article  CAS  Google Scholar 

  9. Ringo, J. L. Brain. Behav. Evol 38, 1–6 (1991).

    Article  CAS  Google Scholar 

  10. Butler, A. B. & Hodos, W. in Comparative Vertebrate Neuroanatomy: Evolution and Adaptation. (Wiley–Liss, New York, 1996).

    Google Scholar 

  11. Cousens, G. & Otto, T. Both pre- and post-training excitotoxic lesions of the basolateral amygdala abolish the expression of olfactory and contextual fear conditioning. Behav. Neurosci. 112, 1092-1103 (1998).

    Article  Google Scholar 

  12. Swanson, L. W. & Petrovich, G. D. What is the amygdala? Trends Neurosci. 21, 323– 331 (1998).

    Article  CAS  Google Scholar 

  13. Barton, R. A., Purvis, A. & Harvey, P. H. Evolutionary radiation of visual and olfactory brain systems in primates, bats and insectivores. Phil. Trans. Roy. Soc. B 348, 381–392 ( 1995).

    Article  ADS  CAS  Google Scholar 

  14. Krebs, J. R. Food-storing birds: adaptive specialization in brain and behaviour? Phil. Trans. Roy. Soc. B 329, 153– 60 (1990).

    Article  ADS  CAS  Google Scholar 

  15. Stephan, H., Frahm, H. D. & Baron, G. New and revised data on volumes of brain structures in insectivores and primates. Folia Primatol. 35, 1–29 (1981).

    Article  CAS  Google Scholar 

  16. Stephan, H., Baron, G. & Frahm, H. D. in Comparative Brain Research in Mammals. Vol. 1: Insectivores (Springer, New York, 1991).

    Google Scholar 

  17. Frahm, H. D., Stephan, H. & Stephan, M. Comparison of brain structure volumes in Insectivora and Primates. I. Neocortex. J. Hirnforsch. 23, 375–389 (1982).

    CAS  PubMed  Google Scholar 

  18. Matano, S., Baron, G., Stephan, H. & Frahm, H. D. Volume comparisons in the cerebellar complex of primates. II Cerebellar nuclei. Folia primatol. 44, 182–203 ( 1985).

    Article  CAS  Google Scholar 

  19. Matano, S. A volumetric comparison of the vestibular nuclei in primates. Folia primatol. 47, 189–203 (1986).

    Article  CAS  Google Scholar 

  20. Felsenstein, J. Phylogenies and the comparative method. Am. Nat. 125 , 1–15 (1985).

    Article  Google Scholar 

  21. Harvey, P. H. & Pagel, M. D. The Comparative Method in Evolutionary Biology (Oxford Univ. Press, Oxford, 1991).

    Google Scholar 

  22. Purvis, A. & Rambaut, A. Comparative analysis by independent contrasts (CAIC): an Apple Macintosh application for analysing comparative data. Comp. Appl. Biosci. 11, 247– 251 (1995).

    CAS  PubMed  Google Scholar 

  23. Purvis, A. A composite estimate of primate phylogeny. Phil. Trans. Roy Soc. B 348, 405–421 ( 1995).

    Article  ADS  CAS  Google Scholar 

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We thank R. Grenyer for permission to use an unpublished phylogeny of insectivores.

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Correspondence to Robert A. Barton.

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Barton, R., Harvey, P. Mosaic evolution of brain structure in mammals. Nature 405, 1055–1058 (2000).

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