Exactly when the first people arrived in the Americas is still hotly debated. Genetic evidence suggests it was between 20 000 and 15 000 years ago, when sea levels were low and land connected Siberia to Alaska. Ice sheets would have covered the interior of North America, forcing the new arrivals to travel down the west coast.

You might need a minute to figure out the map below. Find the number 6, then follow it left to trace the journey down the west coast of North America. The Kennewick site is in Washington State, just south of the west coast of British Columbia.