antecedent
/ˌæn(t)əˈsidnt/
noun
A thing or event that existed before or logically precedes another.
some antecedents to the African novel might exist in Africa’s oral traditions
precursor,forerunner,predecessor
adjective
Preceding in time or order; previous or preexisting.
the antecedent events that prompt you to break a diet
previous,earlier,prior,foregoing,preceding,precursory