A groundbreaking study led by planetary scientists Giovanni Muttoni from the University of Milan and Dennis Kent from Columbia University has provided new insights into the exodus of hominins out of Africa around 1 million years ago. Their research, published in the Proceedings of the National Academy of Sciences, suggests that this migration may have been driven by the onset of the first major glaciation of the Pleistocene epoch.
Previous studies have indicated that a significant migration of hominins out of Africa occurred between 1.1 and 0.9 million years ago, coinciding with a population bottleneck—a sudden decrease in numbers—around the same time. In their study, Muttoni and Kent aimed to better understand the timing and reasons behind this migration.
To achieve this, the researchers analyzed shifts in oxygen isotopes found in rock sediment layers, which allowed them to pinpoint the beginning of the first major Pleistocene ice age to approximately 900,000 years ago. They then revisited prior studies that suggested a population bottleneck occurred roughly 200,000 years earlier. However, they found these results to be unreliable, possibly due to undercounting of population numbers in certain areas.
Turning their attention to the onset of the first Pleistocene ice age, which coincided with the migration of hominins out of Africa, the researchers proposed climate change as the driving force behind the exodus. As the ice age began, dropping ocean levels would have created easier migration routes from Africa to other continents. Additionally, worsening conditions in Africa would have made migration an attractive option for hominins seeking more hospitable environments.
The researchers highlighted that evidence from past research indicated widespread habitation of Eurasia by hominins approximately 90,000 years ago, aligning with the timing of the first Pleistocene ice age. This suggests that climate change played a pivotal role in prompting hominin migration out of Africa.
Furthermore, the team noted that many animal species also began migrating out of Africa around the same time, further supporting the idea of climate-driven migration.
In summary, Muttoni and Kent's study sheds new light on the factors influencing the migration of hominins out of Africa approximately 1 million years ago. By linking the onset of the first major Pleistocene ice age with genetic evidence of population bottlenecks and patterns of hominin habitation, the researchers propose climate change as a key driver of this significant event in human history, occurring around 0.9 million years ago.