Volcanism in Ethiopia speeded early human evolution

The Ethiopian Rift Valley hosts the longest record of human co-existence with volcanoes on Earth. Dramatic and rapid changes from volcanic activity in Ethiopia appear to have set the stage for the emergence of Homo sapiens around 200,000 years ago. According to new research, the first known fossil evidence for our species was unearthed there, where explosive volcanic activity was dramatically changing the landscape and environment[1].

"Pyroclastic flows -- hot currents of gas, ash and rock -- would have inundated large tracts of the rift floor while ash and pumice fallout from larger plumes are likely to have covered regions to at least 100 kilometers from the vent," commented lead author William Hutchison of the University of Oxford's Department of Earth Sciences.

The earliest humanoid fossils date to 195,000 years ago, so early humans likely witnessed the eruptions. Hutchison said that the volcanic eruptions occurred along the entire East African Rift System, which is a still-active continental rift where Africa is slowly being pulled apart. One segment runs through Ethiopia. Hutchison and his team reconstructed the eruptive history of a 124-mile-long segment of the rift in Ethiopia by studying the Aluto and Corbetti volcanoes. The researchers tried to determine the dates of erupted rocks. They also analyzed the sizes of eruptions along the rift over time.

"We suggest that an increased flux of melt from the mantle into the crust generated the large magma chambers that over-pressured and erupted 320,000–170,000 years ago," Hutchison said. "These events are called flare-ups."

“Major volcanic eruptions and the environmental devastation that followed might have greatly reduced hominid populations living in the rift zone," Hutchison said. "The eruptions themselves would have made certain sections of the rift uninhabitable, potentially for many thousands of years. These mechanisms provide a means of reducing and isolating certain populations which might have promoted human adaptation and evolution at this time."

"This suggests," he added, "that our earliest ancestors not only had to deal with changing climate but also with the environmental devastation caused by major explosive eruptions."

Earlier research supports that the region was already heavily populated with hominins long before our species emerged on the scene. Lucy (Australopithecus afarensis) was the only potential human ancestor species that roamed in what is now the Afar region of Ethiopia.

[1] Hutchison et al: A pulse of mid-Pleistocene rift volcanism in Ethiopia at the dawn of modern humans in Nature Communications – 2016