Why do archaeological sites in the Americas suggest that coastal migration occurred early?

Archaeological evidence suggesting early coastal migration in the Americas is primarily inferred from the limitations of interior land-based models and the discovery of sites that predate the traditional Clovis culture.

While early theories emphasized a land-bridge migration from Siberia to Alaska across the Bering Strait, the subsequent flooding of this region has obscured direct evidence of those early arrivals. Furthermore, the presence of humans in the interior of North America was long thought to be restricted by impenetrable glacial formations until the ice retreated.12

The discovery of Monte Verde in Chile, which dates to approximately 10,500 BCE, challenged the timeline of human arrival. Because it seemed unlikely that humans could have migrated from Siberia to South America in only 1,000 years, researchers began to look toward coastal routes as a more viable path for rapid expansion. While the search for coastal sites remains difficult due to rising sea levels, the existence of these early, widespread Pre-Clovis cultures supports the theory that humans moved along the Pacific coast much earlier than previously believed.31