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Enlarged Magnocellular Retinal Ganglion Cells

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Human Uniqueness Compared to "Great Apes": 
Speculative Difference
MOCA Domain: 
Neuroscience
MOCA Topic Authors: 
Todd M Preuss

Magnocellular retinal ganglion cells may have been enlarged in human evolution. Dacey has demonstrated that the magnocellular class of ganglion cells in the retina are larger in humans than in macaques, although the sizes of the parvocellular retinal ganglion cells are very similar. This may reflect an evolutionary specialization of humans for contrast and motion sensitivity, which are mediated by the magnocellular ganglion cells. However, there are no comparable data for hominids other than humans.

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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: 
25000 Thousand Years
Definite Appearance: 
6000 Thousand Years
References: 

Dacey DM, Petersen MR (1992) Dendritic field size and morphology of midget and parasol ganglion cells of the human retina. Proc Natl Acad Sci U S A 89:9666-9670.Preuss TM (2004) Specializations of the human visual system: The monkey model meets human reality. In: The Primate Visual System (Kaas JH, Collins CE, eds), pp 231-259. Boca Raton, FL: CRC Press.