For much of the twentieth century, the prevailing scientific explanation for the peopling of the Americas centered on a single, simplified narrative. According to this model, ancestral populations migrated from Northeast Asia into North America via the Bering Land Bridge—an expanse of land that connected present-day Siberia and Alaska during the last Ice Age. Over thousands of years, these populations gradually dispersed southward, forming the diverse Indigenous cultures known today.

This theory was supported by archaeological findings, linguistic similarities, and later, early genetic studies. It became the foundation of history textbooks, museum exhibits, and academic teaching. While broadly accurate, it also left little room for nuance, regional variation, or the complexity of human migration.

In recent decades, however, scientists have increasingly emphasized that human history is rarely linear. Migration occurs in waves, sometimes overlapping, sometimes reversing, and often involving interaction between distinct groups. As genetic technology has improved, researchers have gained new tools to examine these patterns with greater precision.