Horseback
  cost changed from 250 to 180, but only available later

Masonry 
  from bronze to copper era

Alphabet
  from bronze to iron (to keep techs in each era to a depth of 2)

Priesthood
  from bronze to copper

Writing
  from bronze to copper (to reflect paintings in caves), counting cows, etc.
  requires (AND) mysticism, removed (OR) priesthood prerequisite.

Code of laws
  from bronze to copper (10 commandemnts),
  Changed (OR) to (AND) writing, removed (OR) currency, prerequisite

Drama
  from iron to bronze (greek plays)

Literature
  from iron to bronze (Homers epics)

Philosophy
  requires alphabet, not drama

Civil service
  changed (OR) to (AND) code of laws, removed (OR) feudalism, as feudal societies tended to have codes of laws anyway (not enforced).