After the standstill, when conditions changed enough to allow southward movement — whether through ice-free corridors or along the coast — the isolated founding population expanded rapidly through the Americas.

The scale and speed of this expansion is evidenced by the rapid appearance of human populations from Alaska to the southern tip of South America within a geologically brief period.

The specific timing of the standstill, the southward expansion, and the initial diversification of Native American populations within the Americas is still debated.

What the MA-1 finding confirmed is that the population that underwent the standstill and the expansion was already carrying both East Asian and Ancient North Eurasian ancestry — the dual heritage that the 2014 paper identified and that subsequent research has refined.

After The Americas Were Founded