It has been widely agreed that modern humans first evolved in Africa and have just migrated out around 65,000 to 55,000 years ago. It was even suggested that their route specifically started from East Africa to Arabia.
Moreover, previous study also found that different places in Africa, including Sahara, had may wet and dry phases. This led them to hypothesize that this conditions enabled people to easily move out into Europe and Asia.
To understand this further, Jessica Tierney of the University of Arizona and colleagues utilized 200,000 years old sediments of a marine core collected from the Gulf of Aden off Africa’s east coast in 1965. With this, they were able to create an extended timeline of climate shifts in north-east Africa.
Focusing on alkenone--a chemical made by marine also--they were able to specify temperatures every 1600 years. This is because alkenone's composition changes when sea surface's temperature does. Researchers also utilized wax of leaves that were buried in such sediment to make a rainfall record.
And similar to the previous evidence, results showed that north-east Africa was indeed warm and wet between 130,000 and 80,000 years ago--the same time humans were expanding throughout Africa.
However, the place became dry and cold between 75,000 and 55,000 years ago wherein major migration from Africa happened. This suggests that instead of having a good climate enabling people to easily leave Africa, Tierney says, perhaps difficult climate pushed ancient humans to move out and escape.
“It raises the possibility that drought, rather than rainy conditions, prompted early humans to migrate,” says Tierney.
This interpretation, however, is still up for discussion as the out-of-Africa migration date is still controversial. “I don’t think we can really say that dispersal coincided with North Africa becoming drier and colder,” says archaeologist Huw Groucutt at the University of Oxford.
Nonetheless, this opens a new possibility that may soon lead us to knowing what really happened before everything we have right now became normal. So, here's to understanding further our roots and embracing our oneness!
Get weekly science updates in your inbox!