What is the most widely accepted theory about early human migration to the Americas?

While evidence of animal migration is more solidified, the human story may be more complicated. As of 2008, genetic findings suggest that a single population of modern humans migrated from southern Siberia toward the land mass known as the Bering Land Bridge as early as 30,000 years ago, and crossed over to the Americas by 16,500 years ago. Archaeological evidence shows that by 15,000 years ago, humans had made it south of the Canadian ice sheets.

Explanation:

we need an attachment to see what you are talking about.

an informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.