If people are on the move, the seacoast is a very good place to travel. There is food there all the time.

I used to think of the people who crossed into America in the Ice Ages across the Bering Land Bridge into America as all going on land across the western part of Canada and the US, down onto the deserts of Mexico, and a few of them going through Central America.

Now this seems naive to me. Central America looks like a bottleneck on the map, but it has jus as much coast as the coast-to-coast US or South America. In fact, it may have had twice as much, since travelers doing south in the west could not have used BOTH coasts as they could in Costa Rica. The deserted cities in the Central American jungles had access to two coasts, and people from two coasts might well have wandered inland enough there to meet each other.

But all that history is drowned. Coasts shift all the time while archeologists will only go to places like Egypt where neither new civilizations nor water have disturbed the garbage heaps they mistake for the places human development took place. That leaves out our Aryan, Iranian, Erin (Ireland) history, because we are still building on the locations we live on. It leaves out the entire Black Sea Valley. As technology advances, our present history is going to be a laughing-stock.