Santa Rosa Island is visible from the California mainland on a clear day.

The crossing, in favorable conditions, would not have required navigating blind.

The island’s mountains would have been a landmark guiding the crossing in both directions.

But favorable conditions are not guaranteed, and the history of open-water navigation is partly the history of waiting for favorable conditions and knowing how to recognize them.

The people who crossed to Santarosae 13,000 years ago had the knowledge to make the crossing, make it regularly enough to sustain a population, and make it back.

They were maritime people in the fullest sense — not accidental visitors but intentional travelers using developed skills.