Please help! What natural features affected the route people took from Alaska to southern North America?

Mountains, Rivers, Dry Lands, Swamps Marshes, etc. SO Lanscapes, Temperature, Supply and Trade of goods such as Food, Drinks, clothing and other perishable products, as well as a possible lack of cryptography...aka maps or the MAKING OF new or partial maps for navigation

Explanation:

I answered this question based on the assumption that it was asked in the vain alluding to American Historical aspects m

the answer is use of support