A massive volcanic eruption in Indonesia about 74,000 years ago likely caused severe climate disruption in many parts of the globe, but early human populations were sheltered from the worst effects, according to a new study led by Rutgers.
The eruption of the Toba volcano was the largest eruption in the past two million years, but its impacts on climate and human evolution remain unclear. Resolving this question is important for understanding environmental changes during a key interval in human evolution.
Although climate modeling has suggested the climate consequence could have been severe, the archaeological and paleoclimate records from Africa don’t show such a dramatic response.
“Our results suggest that we might not have been looking in the right place to see the climate response. Africa and India are relatively sheltered, whereas North America, Europe and Asia bear the brunt of cooling,” says study author Benjamin Black, an assistant professor in the Department of Earth and Planetary Sciences at Rutgers University. “One intriguing aspect of this is that Neanderthals and Denisovans were living in Europe and Asia at this time, so our paper suggests evaluating the effects of the Toba eruption on those populations could merit future investigation.”
The results suggest there was likely substantial regional variation in climate impacts. The simulations predict cooling in the Northern Hemisphere of at least 4 degrees Celsius, with regional cooling as high as 10 degrees Celsius depending on the parameters of the model. In contrast, even under the most severe eruption conditions, cooling in the Southern Hemisphere – including regions populated by early humans – was unlikely to surpass 4 degrees Celsuis, although regions in southern Africa and India may have had a decrease in precipitation at the highest sulfur emission level.
The results explain independent archaeological evidence suggesting the Toba eruption had little effects on the development of hominid species in Africa.