Prehistoric sunscreens! Did you know humans had a sun protection secret 40,000 years ago?

Around 41,000 years ago, Earth’s magnetic field weakened dramatically during the Laschamps excursion, reducing to just 10 per cent of its usual strength. Normally, the magnetic field shields the planet from cosmic and solar radiation, but its collapse exposed regions such as Europe and northern Africa to high levels of ultraviolet (UV) radiation. Early humans faced increased risks, including ocular damage and folate depletion, which could lead to birth defects. Researchers at the University of Michigan suggest that Homo sapiens developed behavioural and technological strategies to survive this period, while Neanderthals, lacking such innovations, may have been more vulnerable.

ochre, a red iron-rich pigment Photograph: (Wikimedia Commons)

Ochre and natural sun protection

One key adaptation was the widespread use of ochre, a red iron-rich pigment. Archaeological evidence shows that early Homo sapiens applied ochre to their skin, which experimental studies indicate can act as a natural sunscreen. Previously used in cave art and body decoration, ochre’s sun-protective properties may have offered a critical survival advantage, shielding humans from harmful UV rays during one of Earth’s most intense solar exposures.

Alongside ochre, early humans developed tailored clothing using tools such as needles, scrapers, and awls. Unlike simple coverings, these garments were fitted to the body, providing warmth and indirectly protecting skin from UV radiation. Additionally, the increased use of caves and natural shelters offered further protection from solar exposure. Together, these strategies helped Homo sapiens endure environmental extremes that coincided with the magnetic field’s collapse.

Implications for Neanderthal extinction

The study offers a fresh perspective on why Neanderthals disappeared around 40,000 years ago. Lacking comparable adaptations such as ochre use, tailored clothing, and strategic sheltering, they may have been more exposed to harmful UV radiation. Regions of high cosmic ray exposure during the Laschamps excursion overlap with sites of early modern human activity, suggesting that behavioural and technological innovations contributed to Homo sapiens’ survival advantage.

While the findings are correlational, they highlight early humans’ ability to adapt to extreme environmental stressors. The research also provides insight into potential impacts of future magnetic fluctuations, which could disrupt modern technology and pose risks to human health. Prehistoric sunscreens, tailored clothing, and shelters thus illustrate the ingenuity that enabled our ancestors to thrive under a weakened protective shield.