Strong orbitally induced monsoons facilitated early dispersal of humans to East Asia, study finds

In a study published in Proceedings of the National Academy of Sciencesresearchers have shown that orbital strengthening of the Asian summer monsoon played a key role in the dispersal of Homo sapiens from Africa to East Asia during the last interglacial period ago 125,000 to 70,000 years ago.

Led by Professor Ao Hong of the Institute of Terrestrial Environment of the Chinese Academy of Sciences (CAS), the researchers integrated a comprehensive compilation of paleoanthropological data from sites with new high-resolution reconstructions of the monsoon of Asian summer based on continuous Chinese loess data. modeling the hydroclimate of East Asia and a new simulation of human habitat, all covering the last 280,000 years.

How human ancestors responded to past climate change remains a key question in human evolution research. Climate variability was a key driver of human evolution and dispersal in Africa during the Pleistocene. However, our understanding of the orbital hydroclimatic influence on the early dispersal of our species, Homo sapiens, from Africa to East Asia is hampered by the lack of integrated paleoclimatic and paleoanthropological studies in Asia.

To reconstruct the orbitally resolved variability of the Asian summer monsoon over the past 280,000 years, researchers collected 2,066 field samples from the rapidly accumulating Huanxian loess-paleosol section of China’s central loess plateau. for laboratory measurements.

The resulting unprecedented centennial resolution reconstructions suggest that the orbital-scale variability of the Asian summer monsoon responds to the combined action of changes in insolation (a so-called external forcing, i.e. i.e. coming from outside the Earth), the volume of ice and the greenhouse effect. gas concentration (examples of what we call internal forcings, i.e. those coming from the Earth system), rather than their individual actions. This argument is strongly supported by model-based reconstructions of the hydroclimate of East Asia over the past 280,000 years.

“When we integrated proxy- and model-based spatio-temporal paleoclimatic reconstructions with compilations of paleoanthropological data from Asia across time and space, we discovered, to our surprise, that H. sapiens dispersed into East Asia at the same time as the Asian summer monsoon intensified. This suggests an important influence of the paleo-monsoon on the early dispersal of H. sapiens from Africa to East Asia. East,” Professor Ao said.

“In contrast to the strengthening of the Asian summer monsoon, the climate in much of Southeast Africa deteriorated during the last interglacial. It is possible that these hydroclimatic changes in Asia and South Africa “East, acting together, stimulated the early dispersal of H. sapiens from Africa to East Asia,” said Dr. Thibaut Caley, study author and paleoclimatologist from the University of Bordeaux, France. In contrast, the lush vegetation of East Asia at the time would have attracted the habitation of H. sapiens.

To provide additional quantitative evidence of the effects of climate on the dispersal of H. sapiens, Dr. Ruan Jiaoyang, corresponding author of the study and assistant researcher at the IBS Center for Climate Physics, South Korea, performed simulations computing of H. sapiens habitats and found that the occupation of East Asia by H. sapiens was consistent with a transcontinental increase in simulated habitat quality.