I hear the Bering straight area freezes over every winter and inuits can actually walk across it, so I wonder if god actually separated his two samples before sitting back and watching the experiment.A more interesting question is why the Old World developed faster than the New World. We have here two separate petri dishes of cultural evolution, so there was no (or extremely little) possibility of mutual influence (including everything from sharing ideas to war). The "American Indians" did indeed invent many of the social structures which Old World societies invented, too. Yet, they still moved slower.
If they were, though...the land bridge closed off around 10500 BC, which was around the same time agriculture developed. Back in mesopotamia. So if the bering strait did isolate eurafrasia from the americas, the american peoples would have been set back quite a bit, closed off from the acculturation of farming, which sorta starts the whole city thing, which sorta starts the whole civilization thing. Not only that, but the population would have been far more limited, the small land area of the bering strait acting as a slowdown for the rate of migration, which means that the starting population of america would have been much smaller than the number of humans who would have been around in asia by that time.
Did the american indians move slower or just start slower? I wonder whether the first people to cross the bering strait were post-neolithic peoples; since they were still in the process of migration to new areas, presumably looking for better territory or following game, they hadn't yet developed agriculture.