A higher population in the Pacific Northwest based on fishing in the 3rd or so millennium BCE could lead to further development of NW trade routes and as such earlier contact with the southern cultures and peoples (better trade with California and eventually mesoamerica by proxy) and, perhaps more dramatically, better more sustained contact with Northeast Asia than irl.
A pod involving paleo-Eskimo migration might work?
A pod involving paleo-Eskimo migration might work?