During the LGM the Laurentide Ice Sheet covered most of northern North America while Beringia connected Siberia to Alaska. In 1973, late American geoscientist Paul S. Martin proposed a "blitzkrieg" colonization of the Americas by which Clovis hunters migrated into North America around 13,000 years ago in a single wave through an ice-free corridor in the ice sheet and "spread southward explosively, briefly attaining a density sufficiently large to overkill much of their prey." Others later proposed a "three-wave" migration over the Bering Land Bridge. These hypotheses remained the long-held view regarding the settlement of the Americas, a view challenged by more recent archaeological discoveries: the oldest archaeological sites in the Americas have been found in South America; sites in northeast Siberia report virtually no human presence there during the LGM; and most Clovis artefacts have been found in eastern North America along the Atlantic coast. Furthermore, colonisation models based on mtDNA, yDNA, and atDNA data respectively support neither the "blitzkrieg" nor the "three-wave" hypotheses but they also deliver mutually ambiguous results. Contradictory data from archaeology and genetics will most likely deliver future hypotheses that will, eventually, confirm each other. A proposed route across the Pacific to South America could explain early South American finds and another hypothesis proposes a northern path, through the Canadian Arctic and down the North American Atlantic coast. Early settlements across the Atlantic have been suggested by alternative theories, ranging from purely hypothetical to mostly disputed, including the Solutrean hypothesis and some of the Pre-Columbian trans-oceanic contact theories.
During the LGM the Laurentide Ice Sheet covered most of northern North America while Beringia connected Siberia to Alaska. In 1973, late American geoscientist Paul S. Martin proposed a "blitzkrieg" colonization of the Americas by which Clovis hunters migrated into North America around 13,000 years ago in a single wave through an ice-free corridor in the ice sheet and "spread southward explosively, briefly attaining a density sufficiently large to overkill much of their prey." Others later proposed a "three-wave" migration over the Bering Land Bridge. These hypotheses remained the long-held view regarding the settlement of the Americas, a view challenged by more recent archaeological discoveries: the oldest archaeological sites in the Americas have been found in South America; sites in northeast Siberia report virtually no human presence there during the LGM; and most Clovis artefacts have been found in eastern North America along the Atlantic coast. Furthermore, colonisation models based on mtDNA, yDNA, and atDNA data respectively support neither the "blitzkrieg" nor the "three-wave" hypotheses but they also deliver mutually ambiguous results. Contradictory data from archaeology and genetics will most likely deliver future hypotheses that will, eventually, confirm each other. A proposed route across the Pacific to South America could explain early South American finds and another hypothesis proposes a northern path, through the Canadian Arctic and down the North American Atlantic coast. Early settlements across the Atlantic have been suggested by alternative theories, ranging from purely hypothetical to mostly disputed, including the Solutrean hypothesis and some of the Pre-Columbian trans-oceanic contact theories.