[1][2] The alternative is the hypothesis solely by interior routes, which assumes migration along an ice-free corridor between the Laurentide and Cordilleran ice sheets during the Last Glacial Maximum.
The coastal migration hypothesis has been bolstered by findings such as the report that the sediments in the Port Eliza caves on Vancouver Island indicate the possibility of a survivable climate as far back 16 ka (16,000 years) in the area, while the continental ice sheets were nearing their maximum extent.
[11] In North America, the earliest dog remains were found in Lawyer's Cave on the Alaskan mainland east of Wrangell Island in the Alexander Archipelago of southeast Alaska; radiocarbon dating indicates it is 10,150 years old.
[12] Dating the initial coastal migration is challenging because of the flooding of early settlement sites by the rise of the eustatic sea level accompanying deglaciation.
Dates for sites such as ones at Ground Hog Bay in SE Alaska (10.2 ka) and Namu, about 800 km south of Ground Hog Bay near modern Bella Coola (9.7 ka) thus represent early mainland settlement above the present-day sea level after earlier waterborne migration while the sea level was lower and the coastal mainland was still glaciated.
Full understanding of the initial migration requires careful reconstruction of the land and ecological resources available to the migrants in their contemporary environment.
Evidence from Southeast Alaska and Haida Gwaii (Queen Charlotte Islands) in British Columbia, provides some data about food and land resources during early settlement.
The individual, a young man in his early twenties when he died, has been dated to ≈10,000 cal BP and isotopic analyses indicate he was raised on a diet primarily of marine foods.
[11] These data suggest human occupation when the sea level was lower than present, and that submerged archaeological sites could occur along the paleocoastline beyond the current shorelines of Haida Gwaii (Fedje & Christensen, 1999) and Southeast Alaska.
The antiquity of the lithic scatters that Fedje and Christensen (1999) have found in intertidal zones along the Haida Gwaii coast suggests an early human occupation of the area.
Using linguistic and genetic data as well as dental anthropology, Greenberg et al. subdivided Native Americans into three groups: Amarind, Na-Dene, and Aleut-Inuit.
In 1977, Bonatto and Szathámry (1997) concluded that the presence of glaciers isolated the populations from one another, causing them to settle in Beringia rather than use it as a bridge or corridor for migration to mid-latitude America.
Lesnek et al. 2018 found that the deglaciation of the Pacific coastal corridor allowed for biological productivity, availability of food resources, and an accessible migration route for early colonization.
[21] Even older remains of black and brown bear, caribou, sea birds, fish, and ringed seal have been dated from a number of caves in Southeast Alaska by paleontologist Timothy Heaton.
Sea-going cultures were mobile in the island-rich environment off the late Pleistocene coast of east Asia, facilitating the spread of marine technology and skills through the Philippines, up the Ryukyu chain, to Japan.
Although no boats have been recovered from early Pacific Coast archaeological sites, this may be due to poor preservation of organic materials and the inundation of coastal areas mentioned above.
Significantly, the Channel Islands were not connected to the mainland coast during the Quaternary, so maritime peoples contemporary with the Clovis and Folsom complexes in the interior had to have seaworthy boats to colonize them.
[25] On the Channel Islands, Jon Erlandson and his colleagues have identified several early shell middens located near sources of chert, which was used to make stone tools.