Humans do not gain any special bonuses or abilities, nor do they have special requirements or handicaps.
Maximum CHA: 7
Special abilities: Infravision; +5 save vs. poison.
Maximum CON: 9
Special abilities: Detect secret doors 2 in 6; Glamour gives +1 bonus to reaction rolls.
Maximum STR: 8
Special abilities: +2 AC vs. large creatures, +2 bonus to Stealth checks.
Special abilities: Breathe Fire (as burning hands spell). Breathing fire burns up almost all the chemical energy in the dragonborn's system; after doing so they will be voraciously hungry, and must eat a whole goat (or equivalent meal) to restore their fire breathing capability.
Maximum WIS: 7
Special abilities: No need to eat, drink or breathe; no penalty for fighting unarmed against armed opponents; d6 damage with unarmed attacks; immune to fear.
Handicaps: If reduced to 0 hit points, will perish instantly instead of bleeding out.
Maximum CON: 8
Maximum STR: 11
Special abilities: Shapeshift into any humanoid form.
Handicaps: Hated by all - most NPCs will attack on sight anyone they know to be a Doppelganger.