Researchers have gleaned new insights into the great human migration, revealing how environmental conditions in northern Eurasia and the Americas shaped the journey of ancestors who left Africa tens of thousands of years ago.

The first human migrants favored routes that provided essential resources and facilitated travel, as well as regions with a mix of forests and open areas for shelter and food, while allowing them to expand into new territories.

In Europe, humans likely first spread from the Fertile Crescent through the Caucasus Mountains into Scandinavia approximately 48,300 years ago and Western Europe around 44,100 years ago, following warmer and wetter conditions.

In northern Asia, migration routes followed major rivers to cope with harsher climates before reaching Beringia, a currently submerged land bridge between Siberia and Alaska, approximately 34,700 years ago.

In North America, humans initially migrated along the Pacific coast around 16,000 years ago, and then approximately 3,000 years later, moved inland through the ice-free corridor by the Mackenzie River.

In South America, migration followed wetter grasslands bordering the Amazon, leveraging connectivity provided by major rivers by 14,800 years ago.