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Is the Human Brain Unique?

  • Gerhard RothEmail author
Chapter

Abstract

The human brain is not unique in terms of general structure. It exhibits a morphology typical of mammals and more specific of primates. Also, humans do not have the largest brain either in absolute or in relative terms, although they possess a brain that is seven to eight times larger than expected from general mammalian brain-body relationship. The size of the human cerebral cortex and of the prefrontal cortex as the “seat” of intelligence exhibit a slightly positive allometric growth, i.e. the cortex increases faster in size than the rest of the brain, which is again typical of mammals. Due to a relatively thick cortex and a relatively high neuronal packing density, humans have the highest number of cortical neurons (12–15 billions), which is more than the number of cortical neurons found in cetaceans (whales and dolphins) and elephants with much larger brains up to 10 kg. Furthermore, due to a higher axonal conduction velocity and shorter interneuronal distance, humans have a higher cortical information processing capacity than these large-brained mammals. The largest differences between humans on the one hand and all other mammals/vertebrates on the other consist in (1) a strongly increased growth period of the human brain exposing it to a much higher degree to education, and (2) the presence of the Broca speech center which is a necessary prerequisite of syntactical language and developed only recently, i.e., about 100,000 years ago. While these two traits appear to be minor steps in human biological evolution, they had enormous consequences for human culture and intelligence.

References

  1. 1.
    Blinkov SM, Glezer II (1968) The central nervous system in figures and tables. VEB Fischer-Verlag, JenaGoogle Scholar
  2. 2.
    Changizi MA (2001) Principles underlying mammalian neocortical scaling. Biol Cybern 84:207–215PubMedCrossRefGoogle Scholar
  3. 3.
    Changizi MA (2007) Scaling the brain and its connections. In: Kaas JH, Krubitzer LA (eds) Evolution of nervous systems. A comprehensive review. Vol 3: Mammals. Academic Press (Elsevier), Amsterdam/Oxford, pp 167–180Google Scholar
  4. 4.
    Deacon TW (1990) Rethinking mammalian brain evolution. Am Zool 30:629–705Google Scholar
  5. 5.
    Haug H (1987) Brain sizes, surfaces, and neuronal sizes of the cortex cerebri: a stereological investigation of man and his variability and a comparison with some mammals (primates, whales, marsupials, insectivores, and one elephant). Am J Anat 180:126–142PubMedCrossRefGoogle Scholar
  6. 6.
    Heffner HE, Heffner RS (1995) Role of auditory cortex in the perception of vocalization by Japanese Macaques. In: Zimmermann E, Newman JD, Jürgens U (eds) Current topics in primate vocal communication. Plenum, New York/London, pp 207–219Google Scholar
  7. 7.
    Hofman MA (2000) Evolution and complexity of the human brain: some organizing principles. In: Roth G, Wullimann MF (eds) Brain evolution and cognition. Wiley-Spektrum Akademischer Verlag, New York/Heidelberg, pp 501–521Google Scholar
  8. 8.
    Jerison HJ (1973) Evolution of the brain and intelligence. Academic, New YorkGoogle Scholar
  9. 9.
    Jerison HJ (1991) Brain size and the evolution of mind. American Museum of Natural History, New YorkGoogle Scholar
  10. 10.
    Jerison HJ (1997) Evolution of prefrontal cortex. In: Krasnegor NA, Lyon GR, Goldman-Rakic PS (eds) Development of the prefrontal cortex: evolution, neurobiology, and behavior. Brookes Publishing, Baltimore/London/Toronto/Sydney, pp 9–26Google Scholar
  11. 11.
    Jerison HJ (2000) The evolution of neuronal and behavioral complexity. In: Roth G, Wullimann MF (eds) Brain evolution and cognition. Wiley-Spektrum Akademischer Verlag, New York/Heidelberg, pp 523–553Google Scholar
  12. 12.
    Jürgens U (1995) Neuronal control of vocal production in non-human and human primates. In: Zimmermann E, Newman JD, Jürgens U (eds) Current topics in primate vocal communication. Plenum, New York/London, pp 199–206Google Scholar
  13. 13.
    Kaas JH (1995) The evolution of isocortex. Brain Behav Evol 46:187–196PubMedCrossRefGoogle Scholar
  14. 14.
    Kaas JH (2007) Reconstructing the organization of neocortex of the first mammals and subsequent modifications. In: Kaas JH, Krubitzer LA (eds) Evolution of nervous systems. A comprehensive review. Vol 3: Mammals. Academic Press (Elsevier), Amsterdam/Oxford, pp 27–48Google Scholar
  15. 15.
    Karten HJ (1991) Homology and evolutionary origins of the “neocortex”. Brain Behav Evol 38:264–272PubMedCrossRefGoogle Scholar
  16. 16.
    Marino L (1998) A comparison of encephalization between odontocete cetaceans and anthropoid primates. Brain Behav Evol 51:230–238PubMedCrossRefGoogle Scholar
  17. 17.
    Medina L (2007) Do birds and reptiles possess homologues of mammalian visual, somatosensory, and motor cortices. In: Kaas J, Bullock TH (eds) Evolution of nervous systems. A comprehensive review. Vol 2: Non-mammalian vertebrates. Academic Press (Elsevier), Amsterdam/Oxford, pp 163–194Google Scholar
  18. 18.
    Mrzljak L, Uylings HBM, van Eden CG, Judás M (1990) Neuronal development in human prefrontal cortex in prenatal and postnatal stages. In: Uylings HBM, van Eden CG, de Bruin JPC, Corner MA, Feenstra MGP (eds) The prefrontal cortex. Its structure, function and pathology. Elsevier, Amsterdam/New York/Oxford, pp 185–222Google Scholar
  19. 19.
    Nieuwenhuys R, ten Donkelaar HJ, Nicholson C (1998) The central nervous system of vertebrates, vol 3. Springer, BerlinGoogle Scholar
  20. 20.
    Northcutt RG, Kaas JH (1995) The emergence and evolution of mammalian isocortex. Trends Neurosci 18:373–379PubMedCrossRefGoogle Scholar
  21. 21.
    Pilbeam D, Gould SJ (1974) Size and scaling in human evolution. Science 186:892–901PubMedCrossRefGoogle Scholar
  22. 22.
    Preuss TM (1995) Do rats have a prefrontal cortex? The Rose-Woolsey-Akert program reconsidered. J Cogn Neurosci 7:1–24CrossRefGoogle Scholar
  23. 23.
    Reiner A, Yamamoto K, Karten HJ (2005) Organization and evolution of the avian forebrain. Anat Rec A 287A:1080–1102CrossRefGoogle Scholar
  24. 24.
    Roberts AC, Robbins TW, Weiskrantz L (1998) The prefrontal cortex. Executive and cognitive functions. Oxford University Press, Oxford/New York/TokyoGoogle Scholar
  25. 25.
    Rockel AJ, Hiorns W, Powell TPS (1980) The basic uniformity in structure of the neocortex. Brain 103:221–244PubMedCrossRefGoogle Scholar
  26. 26.
    Rockland KS (2002) Non-uniformity of extrinsic connections and columnar organization. J Neurocytol 31:247–253PubMedCrossRefGoogle Scholar
  27. 27.
    Roth G (2010) Wie einzigartig ist der Mensch? Die lange Evolution der Gehirne und des Geistes. Spektrum, HeidelbergCrossRefGoogle Scholar
  28. 28.
    Roth G, Dicke U (2005) Evolution of the brain and intelligence. Trends Cogn Sci 9:250–257PubMedCrossRefGoogle Scholar
  29. 29.
    Uylings HBM, van Eden CG (1990) Qualitative and quantitative comparison of the prefrontal cortex in rat and in primates, including humans. In: Uylings HBM, van Eden CG, de Bruin JPC, Corner MA, Feenstra MGP (eds) The prefrontal cortex. Its structure, function and pathology. Elsevier, Amsterdam/New York/Oxford, pp 31–62Google Scholar
  30. 30.
    Zhang K, Sejnowski TJ (2000) A universal scaling law between gray matter and white matter of cerebral cortex. Proc Natl Acad Sci USA 97:5621–5626PubMedCrossRefGoogle Scholar
  31. 31.
    Zimmermann E (1995) Loud calls in nocturnal prosimians: structure, evolution and ontogeny. In: Zimmermann E, Newman JD, Jürgens U (eds) Current topics in primate vocal communication. Plenum, New York/London, pp 47–72Google Scholar

Copyright information

© Springer-Verlag Italia S.r.l.  2012

Authors and Affiliations

  1. 1.Brain Research InstituteBremenGermany

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