Astrocyte Morphology

Certainty Style Key
Hover over keys for definitions:
True   Likely   Speculative
Human Uniqueness Compared to "Great Apes": 
Absolute Difference
Human Universality: 
Individual Universal (All Individuals Everywhere)
MOCA Domain: 
MOCA Topic Authors: 

The morphology of astrocytes (one of the major types of central nervous system glial cells) was modified in human evolution. Oberheim and colleagues have noted differences in the morphology of human cortical astrocytes compared to chimpanzees.  

Comparing post-mortum brains with that of over mammals (including apes), these astrocytes are described as having processes that are both longer and wider and a greater proportion of these processes stain for canonical astrocyte marker GFAP+. It is thought that these changes allow for greater calcium transport over a longer distance. This would allow greater signalling capcity at a faster rate through individual astrocytic procresses, as calcium ions(Ca2+)are one of the primary signalling methods in astrocytes. 

 It is important to note that these extra-long astrocytes seem to comprise a specific minority subtype in the human brain; the majority of human astrocytes exhibit normal morphology expected of a brain that size.

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: 
6,000 thousand years ago
Definite Appearance: 
100 thousand years ago

References

  1. Uniquely hominid features of adult human astrocytes., Oberheim, Nancy Ann, Takano Takahiro, Han Xiaoning, He Wei, Lin Jane H. C., Wang Fushun, Xu Qiwu, Wyatt Jeffrey D., Pilcher Webster, Ojemann Jeffrey G., et al. , J Neurosci, 2009 Mar 11, Volume 29, Issue 10, p.3276-87, (2009)
  2. Astrocytic complexity distinguishes the human brain., Oberheim, Nancy Ann, Wang Xiaohai, Goldman Steven, and Nedergaard Maiken , Trends Neurosci, 2006 Oct, Volume 29, Issue 10, p.547-53, (2006)