For decades, archaeologists thought they knew how the story went: Humans migrated from Siberia to Alaska over the Bering land bridge during the last Ice Age, but were stuck there until a corridor opened up between the eastern and western ice sheets covering much of what is now Canada. Then, the Clovis people – thought to be the first to spread across the Americas – took that new path down to the rest of the continent.

But as evidence poured in suggesting people were in the Americas long before the distinctive Clovis spearpoints showed up, the Clovis-first model was discredited.

And now, scientists say that the Clovis people didn’t even arrive via that corridor.

It all comes down to timing, according to new research published Wednesday in the journal Nature. The ice-free corridor through the Canadian cordillera couldn’t have supported human migration until about 12,600 years ago. But the Clovis people were already living south of the ice sheets by 13,500 years ago.