Ice Free Corridor - Clovis Pathway into Americas

Did an Ice-Free Corridor Serve as an Early Pathway into the New World?

Robson Glacier view from Mumm Basin
Robson Glacier view from Mumm Basin near the Continental Divide in Alberta, Canada. Dubicki Photography / Getty Images

The Ice Free Corridor hypothesis has been an accepted route for human colonization of the American continents since at least the 1930s. This route was postulated by archaeologists looking for a way by which humans could have entered North America during the late Wisconsinan ice age. Essentially, the hypothesis suggested that Clovis culture hunters arrived in North America chasing after megafauna (mammoth and bison) through a corridor between the ice slabs. The corridor crossed what is now the provinces of Alberta and eastern British Columbia, between the Laurentide and Cordilleran ice masses.

The Ice Free Corridor's usefulness for human colonization is not questioned: the latest theories about the timing of human colonization have ruled it out as the first pathway taken by people arriving from Bering and northeastern Siberia

Questioning the Ice Free Corridor

In the early 1980s, modern vertebrate paleontology and geology was applied to the question. Studies showed that various portions of the 'corridor' were blocked by ice from between 30,000 to at least 11,500 BP (i.e., during and for a long while after the Last Glacial Maximum). Since archaeological sites in Alberta are less than 11,000 years old, colonization of Alberta had to have occurred from the south, and not along the so-called ice free corridor.

Further doubts about the corridor began to arise in the late 1980s when pre-clovis sites--sites older than even 12,000 years (such as Monte Verde, Chile)--began to be discovered. Clearly, people who lived at Monte Verde could not have used the ice free corridor to get there. The oldest site known along the corridor is in northern British Columbia: Charlie Lake Cave, where the recovery of both southern bison bone and Clovis-like projectile points suggest that these colonists arrived from the south, and not from the north.

Clovis and the Ice Free Corridor

Recent archaeological studies in eastern Beringia, as well as detailed mapping of the route of the Ice Free Corridor, have led researchers to recognize that a passable opening between the ice sheets did exist beginning circa 14,000 cal BP (ca. 12,000 RCYBP). While too late to represent a passageway for preclovis peoples, the Ice Free Corridor, sometimes known as the "western interior corridor" or "deglaciation corridor" may well have been the main route taken by Clovis hunter-gatherers, as suggested by W.A. Johnson in the 1930s.

An alternative route for the first colonists has been proposed along the Pacific coast, which would have been ice-free and available for migration for pre-Clovis explorers in boats or along the shoreline. The change of path is both affected by and affects our comprehension of the earliest colonists in the Americas: rather than Clovis 'big game hunters', the earliest Americans ("pre-Clovis") are now believed to have used a broad variety of food sources, including hunting, gathering, and fishing.


The Ice Free Corridor glossary entry is part of the Guide to the Population of America and the Dictionary of Archaeology.

More details on the problems with the Ice Free Corridor hypothesis can be found in this article written in 2004 for Geotimes by Lionel E. Jackson Jr. and Michael C. Wilson.

Achilli A, Perego UA, Lancioni H, Olivieri A, Gandini F, Hooshiar Kashani B, Battaglia V, Grugni V, Angerhofer N, Rogers MP et al. 2013. Reconciling migration models to the Americas with the variation of North American native mitogenomes. Proceedings of the National Academy of Sciences 110(35):14308-14313.

Buchanan B, and Collard M. 2007. Investigating the peopling of North America through cladistic analyses of Early Paleoindian projectile points. Journal of Anthropological Archaeology 26:366–393.

Hamilton MJ. 2008. Quantifying Clovis Dynamics: Confronting Theory with Models and Data Across Scales. Albuquerque: University of New Mexico.

Heintzman PD, Froese D, Ives JW, Soares AER, Zazula GD, Letts B, Andrews TD, Driver JC, Hall E, Hare PG et al. 2016. Bison phylogeography constrains dispersal and viability of the Ice Free Corridor in western Canada. Proceedings of the National Academy of Sciences.

Hooshiar Kashani B, Perego UA, Olivieri A, Angerhofer N, Gandini F, Carossa V, Lancioni H, Semino O, Woodward SR, Achilli A et al. 2012. Mitochondrial haplogroup C4c: A rare lineage entering America through the ice-free corridor? American Journal of Physical Anthropology 147(1):35-39.

Perego UA, Achilli A, Angerhofer N, Accetturo M, Pala M, Olivieri A, Kashani BH, Ritchie KH, Scozzari R, Kong Q-P et al. 2009. Distinctive Paleo-Indian Migration Routes from Beringia Marked by Two Rare mtDNA Haplogroups. Current Biology 19:1–8.

Waguespack NM. 2007. Why We’re Still Arguing About the Pleistocene Occupation of the Americas. Evolutionary Anthropology 16(63-74).

Waters MR, Stafford TW, Kooyman B, and Hills LV. 2015. Late Pleistocene horse and camel hunting at the southern margin of the ice-free corridor: Reassessing the age of Wally’s Beach, Canada. Proceedings of the National Academy of Sciences 112(14):4263-4267.