atavistic vs throwback

atavistic is not a noun while throwback is a noun.

Word	Noun	Adjective	Verb	Adverb
atavistic	No	Yes	No	No
throwback	Yes	Yes	No	No

As adjectives, atavistic and throwback are synonyms defined as:

atavistic (noun)	throwback (noun)
	a reappearance of an earlier characteristic
	an organism that has the characteristics of a more primitive type of that organism

atavistic (adjective)	throwback (adjective)
characteristic of an atavist	characteristic of an atavist