Humanism can best be described as . an exploration of the biology of human beings an emphasis on life in the present a focus on the afterlife an interest in the diversity of our species

many is the pronoun that is used in this sentence. many is a quantifier that determines the amount of discoveries. when we use quatifiers followed by nouns, they act as determiners, but when they are used without a noun, as it is this case, they are pronouns.