“The skies 41,000 years ago may have been both spectacular and threatening. When we realized this, we wanted to know whether this could have affected people living at the time,” the study authors said.
How did the skies influence early human lifestyle?
The study began with a simple but interesting question. What happens to life on Earth when the magnetic field nearly disappears? To find the answer to this question, the study authors combined climate models and archaeological evidence.
Their focus was the Laschamps Excursion, a brief but extreme event around 41,000 years ago when Earth’s magnetic field weakened drastically. Instead of its usual structure, like a giant bar magnet with a north and south pole, the magnetic field fractured into multiple weak poles scattered around the globe.
At its lowest point, the field strength fell to below 10 percent of today’s levels, leaving Earth exposed to dangerous cosmic radiation and solar winds. Usually, the magnetosphere acts as a protective bubble, shielding us from harmful ultraviolet (UV) rays and charged particles from the Sun.
However, during the Laschamps Excursion, that shield broke down. As a result, auroras that are normally seen only near the poles may have danced across much of the sky, and harmful UV radiation could have penetrated to Earth’s surface at far greater levels than usual.
While this sounds like a scenario from science fiction, it had real and potentially serious consequences for life. Increased UV exposure could have led to sunburn, eye damage, birth defects, and skin diseases. So the researchers asked, could ancient humans have noticed and adapted? The archaeological record provides some interesting clues.
Around this time, evidence shows a rise in the use of deep caves for shelter, the application of ochre-based pigments on skin, and possibly more protective clothing in parts of Europe where the effects would have been strongest.
All these behaviors could have helped shield early humans, both Homo sapiens and Neanderthals, from the sudden spike in solar radiation. However, the researchers are not claiming that the Laschamps Excursion caused Neanderthal extinction or major evolutionary changes of that time on its own.
“We’re not suggesting that space weather alone caused an increase in these behaviors or, certainly, that the Laschamps caused Neanderthals to go extinct, which is one misinterpretation of our research. But it could have been a contributing factor, an invisible but powerful force that influenced innovation and adaptability,” the study author said.