A paper in Current Anthropology from a few months back that, using data on presence of hookworm the pre-Columbian hookworms and "paleoclimate modelling simulations" implies that there were other colonizers of the Americas, other than the Clovis ones who came through the Bering Strait. From the last paragraph:
The Americas might very well have been originally inhabited by humans moving along an interior land route across Beringia at around 13,000 years BP; however, our research indicates that the Clovis people were unlikely carriers of the hookworm, and this suggests that the parasites were introduced by some alternative mechanism. Alternative mechanisms include the possibility that the parasite entered the Americas by an interior route via Beringia during a period of lower sea level but with regional temperatures significantly higher than at 13,000 years BP. The archaeological literature offers a number of possible nonterrestrial routes, including transoceanic contacts between Japan and Central America (Meggers 1975) and coastal routes along the North Pacific (Heusser 1960; Fladmark 1979; Hetherington et al. 2003) and the North Atlantic (Bradley and Stanford 2004). Pointing to paleoparasitological findings, Araujo, Ferreira, and Confalonieri (1981; Araujo et al. 1988) have discussed the possibility of a trans-Pacific introduction.
Parasites, Paleoclimate, and the Peopling of the Americas
Using the Hookworm to Time the Clovis Migration
Alvaro Montenegro, Adauto Araujo, Michael Eby, Luiz Fernando Ferreira, Renée Hetherington, and Andrew J. Weaver
CURRENT ANTHROPOLOGY Volume 47, Number 1, February 2006
Abstract: Paleoparasitological findings and paleoclimate modelling simulations indicate that early peoples migrating via the "Clovis first" route across Beringia into North America could not have traversed the required distance in time to provide a reasonable explanation for the presence of the hookworm in the pre-Columbian Americas. The introduction of the hookworm into the Americas by a land migration at around 13,000 years BP could have happened only under extraordinary circumstances and even then would have required displacement rates that appear to have no parallel in the archaeology of the continent. This implies that while the Clovis people may have been the first migrants to the Americas, they were almost certainly not the only such migrants.