This study, published in Science Advances and spearheaded by experts in engineering and anthropology, suggests that these adaptations may have played a pivotal role in Homo sapiens' endurance across Europe and Asia, even as Neanderthals vanished from the region.
During the Laschamps excursion-a partial magnetic pole reversal that weakened Earth's magnetic field-high levels of ultraviolet radiation penetrated the atmosphere. These increased radiation levels would have posed major health risks, from skin and eye damage to folate depletion. Yet archaeological and modeling data indicate that early modern humans may have countered this with behavioral innovations.
"We found that many of those regions actually match pretty closely with early human activity from 41,000 years ago, specifically an increase in the use of caves and an increase in the use of prehistoric sunscreen," said Agnit Mukhopadhyay, lead author and U-M research affiliate in climate and space sciences and engineering.
Using the Space Weather Modeling Framework, Mukhopadhyay created a dynamic reconstruction of Earth's geomagnetic conditions during the Laschamps event. Working alongside Sanja Panovska from the GFZ Helmholtz Centre in Germany, he overlaid this data with a three-model system capturing the geomagnetic field, solar plasma behavior, and ancient auroral patterns. The resulting 3D map revealed that the weakened field would have exposed wide swaths of Earth, including Europe and North Africa, to direct cosmic radiation.
This scenario aligns with archaeological signs of behavioral shifts among Homo sapiens, including the increasing prevalence of ochre use and the development of tailored clothing. "It's a pretty effective sunscreen, and there are also ethnographic populations that have used it primarily for that purpose," said U-M anthropologist Raven Garvey, citing ochre's protective qualities.
Garvey emphasized the correlation, not causation, behind the findings: "I think it's important to note that these findings are correlational and (ours is a) meta analysis, if you will. But I think it is a fresh perspective on these data in light of the Laschamps excursion."
The research team notes that Homo sapiens, who arrived in Europe around 56,000 years ago, exhibited technological capabilities such as sewing with bone tools, which allowed them to fashion warmer, UV-protective garments. Such advancements could have enabled greater mobility and resilience during a period of heightened solar exposure.
Neanderthals, by contrast, appear to have lacked both the tools and behaviors necessary to mitigate radiation risks. They disappeared from Europe roughly 40,000 years ago, shortly after the peak of geomagnetic disruption.
Mukhopadhyay and his colleagues believe that studying past magnetic excursions offers valuable insights for anticipating the effects of future events. A similar weakening today, he warned, could disable satellites and telecommunication infrastructure globally.
"Many people say that a planet cannot sustain life without a strong magnetic field," Mukhopadhyay noted. "Looking at prehistoric Earth, and especially at events like this, helps us study exoplanetary physics from a very different vantage point. Life did exist back then. But it was a little bit different than it is today."
The interdisciplinary study included contributions from Michael Liemohn, Daniel Welling, and Austin Brenner of Michigan Engineering; Natalia Ganjushkina of both Michigan Engineering and the Finnish Meteorological Institute; Ilya Usoskin of the University of Oulu; and Mikhail Balikhin of the University of Sheffield.
Research Report:Wandering of the auroral oval 41,000 years ago
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