USR1 from Upward Sun River was approximately 11,500 calendar years old.

The Trail Creek child was approximately 9,000 calendar years old.

The difference — approximately 2,500 years — may not sound large in geological terms, but in the context of population history and the time scale of the events being discussed, it is substantial.

If Ancient Beringian ancestry had only been documented in a single very old individual — USR1, at 11,500 years — it would have been possible to interpret the finding as representing a very early and perhaps brief episode in Alaskan prehistory: an early founding lineage that was present initially but was subsequently absorbed into or replaced by the Northern Native American populations that dominate the later Alaskan and broader Arctic archaeological record.

The Trail Creek child changed this interpretation.