Theory 16/Archaeology & Human Origins /Peopling of the Americas/3 min
The Coast Came First
The oldest accepted sites sit inland and are younger than the genetics allow. The missing centuries may be under water.
The first peopling of the Americas was coastal rather than interior, so the earliest archaeological signature is underwater, and the absence of early interior sites is a prediction rather than a problem.
01The evidence
- Southeast Alaska has been identified as essential for the peopling of the Americas, with the coastal route framed as the viable corridor once the ice retreated.NOAA Ocean Exploration
- The kelp highway hypothesis links marine ecology, coastal migration and the peopling of the Americas, proposing that a productive coastal ecosystem supported rapid movement along the coast.EurekAlert
02The tension
Interior sites are younger than the genetic split implies, and the gap is usually filled by invoking a standstill or a slower migration. The coastal alternative explains the gap but is hard to test because the relevant sites are drowned, so it has remained a plausible but under-evidenced alternative.
03The theory
A coastal route is faster and requires less technological adaptation than an interior route, because the marine resources are predictable and similar along the way. A population can move along a coastline without inventing new subsistence strategies.
If the route was coastal, the earliest sites should be on what was then the coast and is now the continental shelf, at depths that correspond to the sea level of the time. The interior sites should postdate the coastal passage, not precede it.
The prediction is that the earliest dates should be found offshore, and that interior sites should show a pattern of radiation from the coast inland rather than the reverse. It also predicts that the earliest coastal assemblages should be similar along the route, because the subsistence base was similar.
The test is expensive but tractable with existing survey technology: target palaeoshorelines at known depths rather than continuing to dig interior sites that cannot predate the route.
04What this is not
Those models place the first movement through an interior ice-free corridor and treat coastal sites as later. This places the first movement on the coast and predicts that the oldest sites are drowned, which inverts where the search should go.
05Predictions
- P1The earliest dated sites should be found on submerged palaeoshorelines, older than any interior site.
- P2Interior sites should show a radiation pattern from the coast inland.
- P3Early coastal assemblages along the route should be similar despite large distances.
06What would refute it
Interior sites that clearly predate the coastal route, with secure stratigraphy, would restore the interior corridor.
07What it would change
It would redirect early-American archaeology offshore, and change how the genetic gap is interpreted.
08Evidence base
- How Southeast Alaska is essential for the peopling of the Americas — NOAAhttps://oceanexplorer.noaa.gov/expedition-feature/22sunfish-features-peopling-americas-peopling/
- The kelp highway hypothesis and the peopling of the Americas — EurekAlerthttps://www.eurekalert.org/news-releases/510738