Laterality and the evolution of the prefronto-cerebellar system in anthropoids

Authors

  • Jeroen B. Smaers,

    Corresponding author
    1. Department of Anthropology, University College London, London, United Kingdom
    2. Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
    • Address for correspondence: Jeroen B. Smaers, Department of Anthropology, University College London, 14 Taviton Street, London, WC1H 0BW, UK. j.smaers@ucl.ac.uk

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  • James Steele,

    1. University College London, Institute of Archaeology, London, United Kingdom
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  • Charleen R. Case,

    1. Florida State University, Department of Psychology, Tallahassee, Florida
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  • Katrin Amunts

    1. Research Center Jülich, Institute of Neuroscience and Medicine INM-1, and JARA-Brain, Jülich, Germany
    2. Departments of Psychiatry, Psychotherapy, and Psychosomatics, University Hospital Aachen, Aachen, Germany
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  • [The copyright line for this article was changed on July 18, 2014 after original online publication.]

Abstract

There is extensive evidence for an early vertebrate origin of lateralized motor behavior and of related asymmetries in underlying brain systems. We investigate human lateralized motor functioning in a broad comparative context of evolutionary neural reorganization. We quantify evolutionary trends in the fronto-cerebellar system (involved in motor learning) across 46 million years of divergent primate evolution by comparing rates of evolution of prefrontal cortex, frontal motor cortex, and posterior cerebellar hemispheres along individual branches of the primate tree of life. We provide a detailed evolutionary model of the neuroanatomical changes leading to modern human lateralized motor functioning, demonstrating an increased role for the fronto-cerebellar system in the apes dating to their evolutionary divergence from the monkeys (∼30 million years ago (Mya)), and a subsequent shift toward an increased role for prefrontal cortex over frontal motor cortex in the fronto-cerebellar system in the Homo-Pan ancestral lineage (∼10 Mya) and in the human ancestral lineage (∼6 Mya). We discuss these results in the context of cortico-cerebellar functions and their likely role in the evolution of human tool use and speech.

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