Magnocellular Retinal Ganglion Cell Size

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Human Uniqueness Compared to "Great Apes": 
Speculative Difference
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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.

Timing

Timing of appearance of the difference in the Hominin Lineage as a defined date or a lineage separation event. The point in time associated with lineage separation events may change in the future as the scientific community agrees upon better time estimates. Lineage separation events are defined in 2017 as:

  • the Last Common Ancestor (LCA) of humans and old world monkeys was 25,000 - 30,000 thousand (25 - 30 million) years ago
  • the Last Common Ancestor (LCA) of humans and chimpanzees was 6,000 - 8,000 thousand (6 - 8 million) years ago
  • the emergence of the genus Homo was 2,000 thousand (2 million) years ago
  • the Last Common Ancestor (LCA) of humans and neanderthals was 500 thousand years ago
  • the common ancestor of modern humans was 100 - 300 thousand years ago

Possible Appearance: 
25,000 thousand years ago
Definite Appearance: 
6,000 thousand years ago
Related MOCA Topics
Referenced By:
Title Certainty
Size of Sensory Thalamic Nuclei Likely

References

  1. Specializations of the human visual system: The monkey model meets human reality , Preuss, T. M. , The Primate Visual System, Boca Raton , p.231-259, (2004)
  2. Dendritic field size and morphology of midget and parasol ganglion cells of the human retina., Dacey, D M., and Petersen M R. , Proc Natl Acad Sci U S A, 1992 Oct 15, Volume 89, Issue 20, p.9666-70, (1992)