For periods beyond the tree-ring record, other sources — including coral records, cave formations called speleothems, and sediment cores — extend the calibration.

When the Trail Creek tooth’s radiocarbon date of 8,085 plus or minus 40 BP is calibrated against the established calibration curve, the result is an age of approximately 9,000 calendar years before present.

This figure — roughly 9,000 years — is the number that places the Trail Creek child in the early Holocene, the period after the end of the last Ice Age when the Bering Land Bridge had already largely submerged and the Seward Peninsula had taken approximately the geographic form it has today.

Nine thousand years is a long time.