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Brain Size

Certainty Style Key
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True   Likely   Speculative
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Absolute Difference
MOCA Domain: 
Neuroscience
MOCA Topic Authors: 
Todd M Preuss

Humans have the largest brains of any primate in absolute terms, as well as relative to body size. Brain size varies with body size - larger bodied species tend to have larger brains. The evolutionary increase in brain size in the hominin lineage, subsequent to the split between humans and chimpanzees, is well documented in the fossil record, with the greatest increase in the last 2 million years with the emergence of the genus Homo.

Related MOCA Topics
Referenced By:
TitleCertainty
AdrenarcheSpeculative
Age of Closure of Fontanelles / SuturesLikely
Brow RidgeSpeculative
CKB (Creatine kinase brain)Speculative
HYDIN (Hydrocephalus inducing homolog)Speculative
Improved Whole Body CoolingNone
Increase in DUF1220 DomainsSpeculative
Lack of Sagittal Crest of SkullLikely
Larger and More Numerous Von Economo (Spindle) CellsLikely
NBPF15 (neuroblastoma breakpoint family, member 15)Speculative
Occipital MorphologyLikely
Organized Gathering of FoodLikely
Parental InvestmentNone
Placement of Foramen MagnumSpeculative
Projection of the external noseLikely
Rate of CNS DevelopmentNone
Requirements at Different Life StagesNone
Small/Large Intestine Length RatioLikely
Smaller Relative Size of the Corpus CallosumTrue
SRGAP2 (SLIT-ROBO Rho GTPase activating protein 2)Speculative
Thyroid Hormone Metabolism Likely
Tool MakingLikely
TTR (transthyretin)None
Timing

Timing of Appearance of the Difference in the Hominin Lineage.

For this entry assume that

  • the common ancestor of humans and old world monkeys was 25000 thousand (25 million) years ago
  • the common ancestor of humans and chimpanzees was 6000 thousand (6 million) years ago
  • the emergence of the genus Homo was 2000 thousand (2 million) years ago
  • the common ancestor of modern humans was 100 thousand years ago

 

Possible Appearance: 
6000 Thousand Years
Probable Appearance: 
2500 Thousand Years
Definite Appearance: 
2000 Thousand Years
Occurrence in Other Animals: 

 Encephalization—increases in brain size corrected for changes in body size—occurred independently in many vertebrate and mammalian groups (Jerison, 1973; Striedter, 2005).  Among mammals, some of the greatest increases in relative brain size occurred in the cetaceans—i.e., dolphins, porpoises, and other toothed whales (Marino et al., 2004).

References: 

Jerison HJ (1973) Evolution of the Brain and Intelligence. New York: Academic Press.Marino L, McShea DW, Uhen MD (2004) Origin and evolution of large brains in toothed whales. The anatomical record 281:1247-1255.Striedter GF (2005) Principles of brain evolution. Sunderland, Mass.: Sinauer Associates.

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