How did Homo sapiens manage to leave Africa around 50,000 years ago, when earlier treks out of the continent had ended in failure?
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An illustration inspired by the prehistoric expansion of humans to different niches in Africa that occurred before a successful global dispersal. (Image credit: Jacopo Niccolò Cerasoni)
Before modern humans began their major dispersal out of Africa about 50,000 years ago, they moved to places that were significantly more ecologically diverse, which may have given them the flexibility they needed to migrate across the globe, a new study finds.
Our species, Homo sapiens, originated in Africa more than 300,000 years ago. Genetic evidence suggests that all modern human populations outside Africa mostly descend from a small group of modern humans who started migrating out of Africa about 50,000 years ago.
However, previous research suggests the first waves of Homo sapiens began leaving Africa as early as about 270,000 years ago. This raises the question of why these earlier migration waves left no genetic traces in modern human populations outside Africa today.
In the new study, published Wednesday (June 18) in the journal Nature, researchers analyzed evidence from archaeological sites across Africa dated to between 120,000 to 14,000 years ago. By examining ancient plant and animal remains, the scientists reconstructed what kinds of habitats and climates people lived in across that span of time — this painted a picture of the vegetation, temperatures and rainfall a given area might have had.
The researchers discovered that modern humans began to expand the range of habitat types in which they lived starting about 70,000 years ago — they went into forests in West and Central Africa, deserts in North Africa, and places with greater ranges of annual temperatures.
“Humans have been successfully living in challenging habitats for at least 70,000 years,” study co-lead author Emily Hallett, an archaeologist at Loyola University Chicago, told Live Science.