The topic of which people settled the Americans is a little outside my field, but I do like to read the latest research on the subject. Many people do not realize that American Indians have a diverse ethnic origin. Some, probably the first, 'native Americans' were Europeans. As early as 20,000 years ago, maybe more, Europeans crossed the ice of the north Atlantic ocean and settled on the east coast. It seems clear now they also crossed from the Bering sea as well, also very early. The evidence of early European settlement is from both archaeological finds and DNA testing.
As a historian, I am familiar with accounts of early European explorers in north America who encountered 'Indians' that appeared fair in skin, had lighter hair, blue or grey eyes. Some past historians were dismissive of these accounts; others attempted to link these 'fair' Indians to the historical period, as in some Medieval event. Both were wrong however. Modern archeology and DNA testing confirms the fact that Europeans lived in the Americas for many thousands of years before Columbus. The post Columbus settlements were the second wave of European movement into the Americas.
Fascination topic to me. Here is a link to a recent article on some of the latest DNA research on American Indian origins.
Ancient DNA Links