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The remarkable, yet not extraordinary, human brain as a scaled-up primate brain and its associated cost
Open accessAbstract
Neuroscientists have become used to a number of “facts” about the human brain: It has 100 billion neurons and 10- to 50-fold more glial cells; it is the largest-than-expected for its body among primates and mammals in general, and therefore the most cognitively able; it consumes an outstanding 20% of the total body energy budget despite representing only 2% of body mass because of an increased metabolic need of its neurons; and it is endowed with an overdeveloped cerebral cortex, the largest compared with brain size. These facts led to the widespread notion that the human brain is literally extraordinary: an outlier among mammalian brains, defying evolutionary rules that apply to other species, with a uniqueness seemingly necessary to justify the superior cognitive abilities of humans over mammals with even larger brains. These facts, with deep implications for neurophysiology and evolutionary biology, are not grounded on solid evidence or sound assumptions, however. Our recent development of a method that allows rapid and reliable quantification of the numbers of cells that compose the whole brain has provided a means to verify these facts. Here, I review this recent evidence and argue that, with 86 billion neurons and just as many nonneuronal cells, the human brain is a scaled-up primate brain in its cellular composition and metabolic cost, with a relatively enlarged cerebral cortex that does not have a relatively larger number of brain neurons yet is remarkable in its cognitive abilities and metabolism simply because of its extremely large number of neurons.
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Metadata
- Authors
- Herculano-Houzel, S.
- Affiliations
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, 21941-902, Rio de Janeiro, Brazil; and Instituto Nacional de Neurociência Translacional, Instituto Nacional de Ciência e Tecnologia/Ministério de Ciência e Tecnologia, 04023-900, Sao Paulo, Brazil
- Venue
- Proceedings of the National Academy of Sciences
- Publisher
- National Academy of Sciences
- Published
- 2012-06-22
- Volume
- 109
- Issue
- supplement_1
- Pages
- 10661-10668
- ISSN
- 0027-8424 (ISSN-L)
- 1091-6490
- PMC
- PMC3386878
- OpenAlex
- W1966084915
- Semantic Scholar
- 65f9d025887298541bab310b071635e4588d2b68
- Cited by
- 726
- References
- 100
- Citations by year
- 2026: 37 · 2025: 69 · 2024: 93 · 2023: 73 · 2022: 58 · 2021: 60 · 2020: 89 · 2019: 51 · 2018: 36 · 2017: 30 · 2016: 38 · 2015: 38 · 2014: 30 · 2013: 19 · 2012: 4
- FWCI
- 4.12
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Proceedings of the National Academy of Sciences (publishedVersion)
- Europe PMC (PubMed Central) (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Primate Behavior and Ecology
- Life Sciences › Neuroscience › Developmental Neuroscience › Neurogenesis and neuroplasticity mechanisms
- Life Sciences › Neuroscience › Cognitive Neuroscience › Neural dynamics and brain function
- Keywords
- human brain, primate brain, brain scaling, brain size, brain energy metabolism, brain energy consumption, cerebral cortex, neuron number, glial cells, brain evolution, cognitive ability
- MeSH terms
- Animals, Brain, Biological Evolution, Humans, Nerve Net, Neuroglia, Neurons, Primates
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