Yesterday's issue of Science reports on finds on California's Northern Channel Islands pointing to early seafaring and a diversified maritime economy of West Coast Paleoindians:

Three archaeological sites on California’s Channel Islands show that Paleoindians relied heavily on marine resources. The Paleocoastal sites, dated between ~12,200 and 11,200 years ago, contain numerous stemmed projectile points and crescents associated with a variety of marine and aquatic faunal remains. At site CA-SRI-512 on Santa Rosa Island, Paleocoastal peoples used such tools to capture geese, cormorants, and other birds, along with marine mammals and finfish. At Cardwell Bluffs on San Miguel Island, Paleocoastal peoples collected local chert cobbles, worked them into bifaces and projectile points, and discarded thousands of marine shells. With bifacial technologies similar to those seen in Western Pluvial Lakes Tradition assemblages of western North America, the sites provide evidence for seafaring and island colonization by Paleoindians with a diversified maritime economy.

While the finds do not predate Clovis sites, this evidence does make the Coastal Migration hypothesis all the more plausible - although it is not direct proof. The Science issue also has a short analysis by Michael Balter, in which several archaeologists state that the find cannot be related directly to the coastal migration: ... other researchers argue that the new sites are too young to tell us much about the routes that the first Americans took more than 14,000 years ago. It’s possible that the Channel Islands people originally stemmed from inland populations that later moved to the coast, these researchers say.

What makes obtaining proof of such early coastal migrations hard is the fact that sea levels have risen about 70 meters since 13,000 years ago. There may be other indications in favor of the coastal migration hypothesis, such as genetic evidence, see e.g. Kemp e.a. 2007. While Kemp e.a. are  hesitant  to  place  an exact date on the peopling of the Americas based on molecular data, other (less reliable?) archaeological finds as well as the general linguistic picture are not consistent with the (in my opinion) shallow  time depth of around 13,000 years of human habitation in the Americas that they propose.

Find the two Science articles here (subscription required):

• Erlandson, Jon M., Torben C. Rick, Todd J. Braje, Molly Casperson, Brendan Culleton, Brian Fulfrost, Tracy Garcia, et al. 2011. Paleoindian Seafaring, Maritime Technologies, and Coastal Foraging on California’s Channel Islands. Science 331, no. 6021 (March 4): 1181 -1185.
• Balter, Michael. 2011. Do Island Sites Suggest a Coastal Route to the Americas? Science 331, no. 6021 (March 4): 1122.

And some more readings:

• Paul Mann - HSU Don Pinpoints Prehistoric Evidence of Coastal Peoples
• University of Oregon. 2011, March 4. California Islands Give Up Evidence of Early Seafaring: Numerous Artifacts Found at Late Pleistocene Sites on the Channel Islands. ScienceDaily.
• Kemp, Brian M., Ripan S. Malhi, John McDonough, Deborah A. Bolnick, Jason A. Eshleman, Olga Rickards, Cristina Martinez-Labarga, et al. 2007. Genetic analysis of early holocene skeletal remains from Alaska and its implications for the settlement of the Americas. American Journal of Physical Anthropology 132, no. 4 (4): 605-621.