abiogenist - a believer in abiogenesis

apostle - an ardent early supporter of a cause or reform; "an apostle of revolution"

colonialist - a believer in colonialism

Confucian - a believer in the teachings of Confucius

imperialist - a believer in imperialism

Malthusian - a believer in Malthusian theory

admirer, booster, protagonist, supporter, champion, friend - a person who backs a politician or a team etc.; "all their supporters came out for the game"; "they are friends of the library"

vitalist - one who believes in vitalism