There are some obvious possibilities in the news recently, like Kennewick Man, who predates Columbus by several thousand years. One National Park Service memo (follow the link above to this and other bits about him) The BA date (Beta-133993) gave a conventional radiocarbon age of 8410 +/- 40 BP (Hood 1999a and Attachment 1). The equivalent calibrated radiocarbon age (using the two sigma, 95% probability) in years BP is cal BP 9510 to 9405 and cal BP 9345 to 9320. The question then arises, what was he doing here, was he alone, what did he bring with him? (Since "BC" is not used much any more in scholarly applications, there is a collection of terms. I think "BP" is something like "Before Present" era (meaning BC without mentioning Mr. C.) So you're looking at a traveller who might have come through the area 11,400 years ago or so.

I've seen programs recently also about European mummys turning up in China. NOVA ran a program about it. Trade is once again considered a major factor in the travels of these individuals.

All of this is a tangle when doing a web search. The beginning dates of humans in the New World is as big a question as how they got here and how often they made the trips back and forth.

My information about early travel to the New World comes through American Indian literature classes, and the material that surrounds the study of the origin stories of many tribes or nations.

There is one book that I can think of off the top of my head that explores the (possible) results of early European visits to the New World (going back to the times of the Vikings and the sea-going Irish and Spanish who are presumed to have landed here while fishing long before Columbus made his trips). That's Keepers of the Game: Indian-Animal Relationships and the Fur Trade by Calvin Martin. It has been several years since I read this, but I believe he backs up these contacts to well before Columbus' travels, and he suggests that the main reason for these early contacts was for trade. (Some of his conclusions at the end of the book are rather over-the-top, but the research he presents up to that point is interesting.)

It's quite an interesting subject, hampered primarily by the skimpy evidence since any perishable trade goods are not extant today. But that doesn't mean they weren't traded, just that it's difficult to prove. Personally, I think that given the curiosity and resourcefulness of humans, it is almost safer to assume that they did make trade trips a long time ago than that they didn't. Modern humans are so hung up on their technology that they seem to think humans didn't figure out how to get around before the manufacture of iron or the invention of the internal combustion engine.

SRS