Asian monsoon changes led to ancient human migration: study

Scientists have found that the Asian summer monsoon had a big part in helping early humans move from Africa to East Asia around 125,000 years ago. This was a time known as the last inter-glacial period when the Northern Hemisphere was fully covered in ice.

Monsoon helped early humans migrate

The research was led by Professor Ao Hong from the Chinese Academy of Sciences. They used data from a new site related to the Asian summer monsoon and created models of East Asian weather and new settlement simulations covering the last 280,000 years.

Understanding how our ancestors dealt with climate changes is a key question in human evolution research. Climate changes during the Pleistocene epoch led to human development within Africa and their movement to different areas.

But, our knowledge about how these climate changes affected the early movement of Homo sapiens from Africa to East Asia is limited because we don’t have enough studies related to Asia.

The researchers collected 2,066 samples from the Huanxian loess-paleosol section on the central Chinese Loess Plateau. These samples helped them understand changes in the Asian summer monsoon over the past 280,000 years.

The researchers used a climate simulation model and existing environmental reconstructions to combine this record and make estimates for annual rainfall, summer temperature, and other climate variables.

“It’s a great paper,” says Hung Nguyen, a hydrology researcher at Columbia University’s Lamont-Doherty Earth Observatory who did not contribute to the research. “The models and the proxies align quite well.”

Their findings show that changes in the Asian summer monsoon are caused by changes in the sun’s heat, ice volume, and the greenhouse effect. This is supported by the team’s model-based reconstructions of East Asian weather over the past 280,000 years.

Rain, water made settlement suitable

“Now we can confidently add rain and water to the equation that makes environment more suitable for H. sapiens settlement,” says study author María Martinón-Torres, an anthropologist with Spain’s National Research Center on Human Evolution.

Meanwhile, over the same time span, climate in southeastern Africa worsened, the authors found, perhaps pushing humans to find new homelands.

“When you have such a strong climatic phenomena as the monsoon, it would be surprising if you didn’t find influence on how … and where these people lived,” adds study author Tara Jonell, a geologist at the University of Glasgow.

The researchers were surprised to find that Homo sapiens moved into East Asia at the same time as the Asian summer monsoon got stronger. This suggests that the monsoon had a big influence on the early movement of Homo sapiens from Africa to East Asia.

During the last interglacial, the climate in much of south-east Africa got worse while the Asian summer monsoon got stronger. These changes in Asia and south-east Africa might have worked together to push the early movement of Homo sapiens eastward from Africa.

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