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The First Human Colonization of the Americas:
Evaluating the Coastal Migration Hypotheses
E. James Dixon, Professor of Anthropology
University of Colorado Museum and Institute of Arctic and
Alpine Research
The coastal migration hypothesis for the earliest
human migration to the
Americas postulates that people using watercraft first colonized the
southern margin of Beringia and moved south along the Pacific coast
of
the Americas. Evaluating the evidence for this hypothesis relies on
dating geological events, human remains, artifacts, and evaluating
paleoecological evidence. This and other research suggests humans
probably arrived in the Americas no more than about 14,000 (16,250
cal
BP) or 15,000 radiocarbon years ago (16,950 cal BP). When
radiocarbon
dates (RCYA – radiocarbon years ago) are calibrated to calendar
(cal)
years it is apparent that there is more time for human colonization
and
settlement than is suggested by using only the radiocarbon time
scale.
Minimum limiting dates on human remains suggest that the initial
colonization of North America occurred shortly after the LGM,
possibly
no more than a few thousand years prior c 11,500 RCYA (13,050 cal BP).
No reliably dated human remains from the Americas are older than
about
11,500 – 11,000 RYCA (13,050 – 12,550 cal BP).
Recent research demonstrates that unglaciated refugia existed along
the
northwest coast of North America during the LGM and deglaciation had
begun by about 14,000 ^14 C years ago (16,800 cal BP). Deglaciation
was
sufficiently advanced to enable humans using watercraft to colonize
coastal areas by 13,000 radiocarbon years ago (15,350 cal BP). While
the
mid-continent of northern North America remained blocked by ice, off
shore islands and areas of the continental shelf along the Northwest
Coast were ice free beginning about 14,000 RCYA. Archeological
evidence
along ancient shorelines is difficult to detect because rising sea
level
after the LGM submerged much of the Pacific continental shelf. Most
potential research locales are under water making survey difficult
and
expensive.
Human remains of an adult male excavated from On Your Knees Cave,
Prince
of Wales Island, Southeast, Alaska are ^14 C dated to circa 9,800 BP
(10,300 marine corrected cal BP). δ^13 C and δ^15 N values
demonstrate a
diet based on marine foods. Trace element analyses document two “off
island” sources for obsidian from the same stratigraphic level.
These
data suggest that by 10,300 years ago humans along the Northwest
Pacific
Coast were coastal navigators, practiced a maritime economy, and had
established trade networks between islands and the mainland for
obsidian. These data imply earlier human occupation necessary to
establish this broad regional adaptation prior to 10,300 CYA and
strengthens the theory that humans may have first entered the
Americas
using watercraft along the Northwest Coast of North America during
the
late Pleistocene
The traditional interior mid-continental model for human
colonization of
the Americas requires an economy based on hunting terrestrial
mammals,
possibly fresh-water fishing, and pedestrian travel. The coastal
hypothesis suggests an economy based on marine mammal hunting,
salt-water fishing/shellfish gathering, and the use of watercraft.
It is
important to address these hypotheses because each requires
different
types of adaptations by the New World founding population and
established the foundation for all subsequent cultural development
in
the Americas.
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