Some 13,000 years ago, small bands of Stone Age hunters walked across a land bridge between eastern Siberia and western Alaska, eventually making their way down an ice-free inland corridor into the heart of North America.
A subsequent theory, known as the “Kelp Highway,” came closer to the mark: As the massive ice sheets covering western North America retreated, the first humans arrived on the continent not only by foot but by boat, traveling down the Pacific shore and subsisting on abundant coastal resources.
