The search for archaeological evidence to support the coastal route hypothesis is hampered by the fact that the coastline along which early people would have traveled was very different than the Pacific coastline today. At the time when the first people may have been making their journey to North America, much of the earth's water was trapped in glacial ice, lowering sea levels around the world by as much as 100 – 150 meters. Vast expanses of now-drowned lands were exposed, including the Bering Land Bridge that once connected Siberia and Alaska, and large tracts of continental shelf off the coast of the Pacific Northwest. It was along this ancient coastline that early people would have traveled, but as the glacial ice melted and sea levels rose, this coastline was drowned, along with any archaeological remnants of a human presence. In order for archaeologists to find evidence in support of the coastal route, they must first find the now-submerged coast.
The identification of ancient coastlines is a complicated process. Although sea levels were generally lower during the ice age, in some areas of the Pacific Coast they were actually higher than today. This is due to a phenomenon known as isostatic depression, which occurs when the weight of glacial ice pushes the land downward, causing relative sea levels to rise. When the ice melts, the land rebounds upward. While many ancient coastal sites may today be drowned beneath meters of ocean water, others may be stranded far inland in dense coastal rainforest.
In order to overcome these difficulties, geologists have created detailed localized sea level charts for many areas of the coast, and this data is used to reconstruct the ancient shorelines. Remote sensing of the sea floor off Haida Gwaii has led to the identification of ancient riverbeds and forest floors, providing more clues as to the possible location of archaeological sites.
The investigation of these ancient coastlines is incredibly difficult. Reconstructions place the depth of some of these river drainages and ancient terraces are 50 meters below the modern ocean. The depth and the cold water make any underwater excavation nearly impossible, but a tantalizing glimpse of what may lay just below the ancient riverbeds has been uncovered. Using reconstructed maps of the paleoenivroment and landscape, Daryl Fedje and a team of archaeologists from the Canadian National Parks Service dropped a clamshell bucket over 50 meters from the deck of a Coast Guard vessel. When the bucket was retrieved, the team meticulously screened the collected soil sediment from the ocean bed, uncovering a single, unmistakable artifact. Though this was a test, the retrieval of a slate blade from 50 meters below the surface demonstrates the likelihood that humans were occupying these ancient exposed coastlines.
These techniques have narrowed the search, but much more work remains to be done before conclusive archaeological evidence in support of the coastal route is found.
Reconstruction of coastline of northern BC and Haida Gwaii
© Renée Hetherington, J. Vaughn Barrie, Roger MacLeod, and Michael Wilson,
2004. Quest for the Lost Land. Geotimes 49 (2): p. 20-23.