earlier vs in the first place

earlier is an adjective but in the first place is not an adjective.

Word	Noun	Adjective	Verb	Adverb
earlier	No	Yes	No	Yes
in the first place	No	No	No	Yes

As adverbs, earlier and in the first place are synonyms defined as:

Other synonyms of earlier include in the beginning, originally, to begin with.

earlier (adjective)	in the first place (adjective)
(comparative and superlative of `early') more early than; most early

earlier (adverb)	in the first place (adverb)
earlier in time; previously	of primary import
comparatives of `soon' or `early'	before now
before now