Trump started his campaign with the astonishing statement that "They're not sending their best." A few weeks ago he wondered why it's only shithole countries that send people here, why nobody from Norway? Ignoring the obvious racism underlying both statements and many others, it expresses a deep misunderstanding of what emigration is. People don't leave their home because some central authority is ordering them to (although there are a few exceptions: the Trail of Tears, Slavery of Africans, a few others). Leaving home is traumatic. You don't do it unless there's a pretty good reason. The families of three of my four grandparents all came here because they believed it was likely that someone in the old country would kill them--not because they'd done anything wrong, but because of their ethnicity. People leave the old country because there's a war happening, as presently in Syria and several Latin American countries, or because there's a famine or some other terrible circumstance. A tiny fraction of people leave the old country even though they were doing ok in the old one because there's a terrific opportunity in the new one. High tech "brain drain" is one of the few examples of this. People aren't leaving Norway for a very simple reason: Norway has one of the strongest economies in the world and has among the best social safety nets--so even if things aren't going so well for you, Norway is a good place to be.
The big excitement of the moment in anthropology is the discovery that rather than a single wave of emigration from Africa, there is clear evidence that there have been many waves of emigration that took place over many thousands of years. There's even a little evidence that there may have been humans in America 130,000 years ago, ten times what had previously been thought.
I find myself astonished that anybody ever thought that there was a single wave. The forces that drive emigration--famine, war, the search for a better opportunity--are driven by individuals, not by some central organizing force. Africa is a big continent. The first humans probably spread from wherever they evolved to somewhere nearby. The grass may have been greener, hunting may have been better, another tribe or species was out competing them or killing them and they wanted to get away. Before long, some group found their way to other continents. Surely this happened thousands of times over a hundred thousand years.
Humans are naturally curious, and some humans are more curious than others. The first Americans to explore the west were more curious about what lay over the next hill than they were hungry or desperate. With very few exceptions, this was an internal thing. They had unquenchable wanderlust. Even Lewis and Clark were doing it because they wanted to--the sponsorship made the trip easier. The first explorers, 100,000 years ago or more, surely were the prehistoric version of James Bridger and Lewis and Clark. It's easy to imagine some band, or possibly even an individual, driven by wanderlust or perhaps their raft was simply blown off course, finding their way to America, and unable to get back, or perhaps uninterested, making the best of it. Most such bands died out, just as the 11th century Vikings who settled in Newfoundland did. But a few made it.
