The question of how long this complex of Northwest Coast cultures had been developing — how long the specific peoples of the coast had been present in their current homelands — was, before the ancient DNA work, only partially addressed.

The archaeological record of the Northwest Coast extends back to the early Holocene, with sites along the British Columbia and Alaska coast documenting human presence from the early post-glacial period.

But the specific question of biological continuity — whether the people who inhabited the coast 10,000 years ago were the direct biological ancestors of the people who inhabited it at the time of European contact — required genetic evidence to address.

The possibility of population replacement — scenarios in which earlier coastal populations were replaced by later arriving groups — was one of the alternatives that the genetic evidence could in principle distinguish from a scenario of continuous ancestry.