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True   Likely   Speculative
Human Uniqueness Compared to "Great Apes": 
Likely Difference
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Psoriasis is a chronic skin condition affecting about 2% of the human population, typically associated with raised, demarcated, red sking patches that have silvery scales over them.  While the underlying cause is unknown there is evidence for a immune reaction, with a prominent contribution of T cells.  The disease appears to be very rare in great apes.


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
Probable Appearance: 
200 thousand years ago
Definite Appearance: 
100 thousand years ago
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  1. Psoriasis., Nestle, F. O., Kaplan D. H., and Barker J. , N Engl J Med, 07/2009, Volume 361, Issue 5, p.496-509, (2009)
  2. [Psoriasis in a female chimpanzee]., Biella, U, Haustein U F., Seifert S, Adler J, Schüppel K F., and Eulenberger K , Hautarzt, 05/1991, Volume 42, Issue 5, p.322-3, (1991)