Organization of Layer 4A of Area V1

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Human Uniqueness Compared to "Great Apes": 
Likely Difference
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Layer 4A of the primary visual area (V1; area 17; striate cortex) has a distinctive organization in humans: a meshwork of neurons and neurites that express markers for the magnocellular visual pathway (Cat-301, nonphosphorylated neurofilament protein (NPNF), microtubule-associated protein 2 (MAP2)), embedded within which are clusters of small, calbindin-containing neurons.  Chimpanzees, Old World monkeys, and New World monkeys do not exhibit significant expression of Cat-301 in layer 4A, and the organization of neurites expressing NPNF and MAP2 is different in nonhuman primates.


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: 
6,000 thousand years ago
Definite Appearance: 
100 thousand years ago
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Topic Certainty
Size of Sensory Thalamic Nuclei Speculative


  1. Distinctive compartmental organization of human primary visual cortex., Preuss, T M., Qi H, and Kaas J H. , Proc Natl Acad Sci U S A, 1999 Sep 28, Volume 96, Issue 20, p.11601-6, (1999)