MANNERS:
A characteristic or customary mode of acting: custom: a mode of procedure or way of acting: fashion: method of artistic execution or mode of presentation: style: social conduct or rules of conduct as shown in the prevalent customs: characteristic or distinctive bearing, air, or deportment: habitual conduct or deportment: behavior: good manners: a distinguished or stylish air.
CIVILIZATION:
A relatively high level of cultural and technological development; specifically: the stage of cultural development at which writing and the keeping of written records is attained: the culture characteristic of a particular time or place: the process of becoming civilized: refinement of thought, manners, or taste: a situation of urban comfort.
Yes, manners are necessary for civilization, as they are mentioned in both of the above definitions. My own definition of civilization? Everything that the definitions mentions, especially comfort (contented well-being).