Have scientists studied the following...

[25 going on 65]

Sorry if someone already mentioned this, but it seems relevant to the discussion:

From what I understand, hairs on the back and sides of the head aren't immune to the miniaturization process, just extremely resistant. There are some MPB sufferers who experience considerable thinning in the "horse shoe region" (not sure if it's just miniaturization or if it includes actual shedding).