The coastal route hypothesis is based on the premise that the first arrivals in North America did not arrive on foot via an inland route, but instead traveled by boat down the Pacific coast, occupying small pockets of unglaciated land, called refugia, along the outer coast. Once they arrived south of the ice sheets, some groups then made their way inland, possibly via major river systems such as the Columbia. These groups were the ancestors of the people who later made and used the Clovis spear points.
This hypothesis was first proposed in the 1960s when research into ancient plant remains offered evidence that some parts of the outer Pacific Northwest coast had escaped the Cordilleran ice sheet, providing habitable areas, or refugia, for plants, animals and possibly, humans. Archaeologist Knut Fladmark further developed and advanced this hypothesis in the late 1970s, but it did not meet with significant acceptance in the archaeological community until much later.
If the Pacific coast was the point of entry for the first Americans, we would expect to find:
- Evidence of archaeological sites of sufficient antiquity to account for the first arrivals in North America
- Evidence that areas of ice-free land capable of supporting human populations existed along the coast during the Ice Age
- Evidence that early people had what archaeologists call a maritime adaptation – in other words, they had the tools and skills to harvest resources from the sea, such as fish, shellfish and sea mammals, and the tools and skills to manufacture and use some form of watercraft.
Archaeologists, geologists and other researchers are looking for this evidence, but sea level changes over time and poor preservation conditions make it a difficult task.