Its specific mechanisms, timing, and the exact nature of the watercraft and subsistence strategies involved remain subjects of active research and debate.

Arlington Springs contributes one data point: by approximately 13,000 years ago, someone was on a California island that required crossing open water.

This is consistent with — and most easily explained by — a maritime tradition already established on the Pacific coast.

It does not, by itself, prove the Kelp Highway hypothesis.

The Chronostratigraphy That Sealed The Case

The geological fieldwork that returned to Arlington Canyon in the years after the initial bone-chemistry dating was essential for converting a good radiocarbon date into a fully defensible scientific conclusion.

A radiocarbon date from a bone sample tells you when the bone protein last exchanged carbon with the atmosphere — when the animal died.