The Sunscreen That Saved Humanity: How Ochre May Have Helped Homo Sapiens Outlast the Neanderthals

The very short version: around 41,000 years ago, Earth’s magnetic field went through a temporary partial reversal called the Laschamps excursion. During this event, the magnetic field dropped to about 10 percent of its normal strength. That shield is what deflects solar radiation from reaching the surface. With it weakened, UV exposure across Europe and northern Africa increased dramatically.

Neanderthals, who had been living alongside our ancestors in Europe, disappeared around 40,000 years ago. Homo sapiens did not. A team of researchers at the University of Michigan published a study in April 2025 in Science Advances arguing that ochre, a naturally occurring pigment that functions as a sunscreen when applied to skin, may be part of the reason why.

What the Laschamps Excursion Actually Was

Earth’s magnetic poles have flipped at least 180 times throughout geological history. Most of these are full reversals: north becomes south, south becomes north. The Laschamps excursion was something slightly different, a temporary partial collapse and wandering of the field that lasted somewhere around 1,000 years before mostly recovering.

During the excursion, the auroral oval, the atmospheric region where charged solar particles normally concentrate near the poles, expanded and wandered south toward Europe. Solar and cosmic radiation that would normally get deflected streamed through to lower latitudes. The researchers modeled which regions experienced the most severe increase in UV and cosmic ray exposure. The regions that came out most affected were Europe and northern Africa, which are precisely where Homo sapiens and Neanderthals were both living at the time.

What the Archaeological Record Shows

Here is where it gets interesting. Alongside the models of the Laschamps excursion’s effects, the researchers looked at what the archaeological record shows Homo sapiens doing around 41,000 years ago.

Two things stand out. First, evidence of tailored clothing appears in the archaeological record from this period, specifically tools associated with sewing, including needles and awls. This suggests Homo sapiens were making fitted garments that covered the skin, not just rough animal hides thrown over the shoulders.

Second, ochre use increased significantly among Homo sapiens populations during this same window. Ochre is a naturally occurring iron oxide mineral that produces red, yellow, and brown pigments. Archaeologists have long assumed our ancestors used it primarily for symbolic and decorative purposes, body painting, cave art, burial rituals. However, experimental studies have confirmed that ochre applied to skin functions as a reasonably effective sunscreen. Some ethnographic communities still use it for exactly that purpose today.

The researchers’ argument is not that ochre was definitely used as sunscreen. It is that the timing is striking. A period of dramatically increased UV exposure coincides with a documented increase in ochre use by the population that survived and a lack of similar evidence among the population that did not.

The Neanderthal Side of It

Neanderthals were not technologically unsophisticated. They made tools, used fire, buried their dead. Some evidence suggests they used ochre as well, though less consistently and with different patterns than contemporary Homo sapiens.

What the current evidence does not show is Neanderthals making tailored clothing or substantially increasing ochre use during the Laschamps excursion period in the same way Homo sapiens did. The researchers are careful to note that this absence of evidence is not conclusive proof of absence. Archaeological records from 41,000 years ago are incomplete.

Nevertheless, the pattern is there. Homo sapiens adapted their behavior in ways that would have provided meaningful protection against increased radiation. Neanderthals, as far as we can currently tell, did not adapt in the same ways. Whether that gap contributed to their extinction is the hypothesis the study is proposing.