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.
Uniquely hominid features of adult human astrocytes., , J Neurosci, 2009 Mar 11, Volume 29, Issue 10, p.3276-87, (2009)
Astrocytic complexity distinguishes the human brain., , Trends Neurosci, 2006 Oct, Volume 29, Issue 10, p.547-53, (2006)