I suspect that the new discoveries in tracing human genomes out of Africa has overcome the theories that Heyerdahl postulated.

While the research is ongoing, I recall a wonderful show on the Discovery Channel about the Eve Project in which original DNA from the most primative African sources are being traced to all parts of the globe. As I recall, the American Indians were simply the second to last of several migrations, including one by Polynesians, which traveled down to the tip of South America, and predated the Bering Strait bunch by several thousands of years. This information would turn Heyerdahls theory on it's ear, as he had the Peruvians populating the Pacific and not the other way round.

Still, it was a wonderful adventure, and his book was a birthday present to me in my childhood...