A general term for the prehistoric period intermediate between the earliest period (‘[http://en.wikipedia.org/wiki/Paleo-IndianPaleo-Indian]’, ‘Paleo-American’, ‘American‐paleolithic’, &c.) of human presence in the Western Hemisphere, and the most recent prehistoric period (‘Woodland’, etc.).
"The archaeologist corrected her notes to describe the site as belonging to an archaic culture rather than a Paleo-Indian one."
so extremely old as seeming to belong to an earlier period
"a ramshackle antediluvian tenement"
"antediluvian ideas"
"archaic laws"
Of or characterized by antiquity; old-fashioned, quaint, antiquated.
"The village inn was filled with archaic furniture that made the visitors feel like they had stepped back a century."
The word archaic comes from the French archaïque and ultimately traces back to Ancient Greek, where it originally meant "old-fashioned." Its root meaning is simply "from the beginning," referring to something ancient or antiquated.