The disappearance of Neanderthals could be linked to a reversal of the magnetic poles.
Although archaeological data regarding Neanderthals has accumulated over the past few years, allowing archaeologists and anthropologists to paint a more accurate picture of this ancient people, the causes of the disappearance of Neanderthals remain uncertain.
Based on geophysical and atmospheric records dating back more than 40,000 years, researchers recently proposed that this disappearance may be in part due to the consequences of a reversal of the Earth’s magnetic poles.
The shift of the Earth’s magnetic poles, combined with a drop in solar activity 42,000 years ago, could have generated an apocalyptic environment that would have played a role in significant events, ranging from the extinction of the megafauna at the end of the Neanderthals, according to the researchers.
Earth’s magnetic field acts as a protective shield against harmful cosmic radiation. Still, when the poles change, as has happened several times in the past, the protective shield weakens considerably and leaves the planet exposed to particles of high energy.
The Adams Event: Significant Planetary Impact
A temporary pole reversal, known as the Laschamps Excursion, occurred 42,000 years ago and lasted around 1,000 years. Previous work found little evidence that the event had a profound impact on the planet, possibly because the focus was not on the period during which the poles moved, according to the study.
Scientists now say that the inversion, coupled with a period of low solar activity, could have been the source of a wide range of climatic and environmental phenomena with dramatic ramifications. “It probably would have seemed like an apocalyptic end,” says Professor Chris Turney of the University of New South Wales.
Graphs showing the evolution of the magnetic field, solar activity and cosmic radiation on the planet during the magnetic pole reversal 42,000 years ago. This conjunction of several phenomena would have led to significant climatic changes that contributed to the disappearance of Neanderthals.
Laschamp Excursion: Context of Substantial Climatic Incidents
This allowed them to track the increase in carbon-14 levels in the atmosphere over time, produced by increasing levels of high-energy cosmic radiation reaching Earth throughout the Laschamps excursion. As a result, they could date atmospheric changes with more detail than those offered by previous documents, such as mineral deposits.
They then examined many sites and materials worldwide, including lake and ice cores, and found that a host of significant environmental changes occurred as carbon-14 levels peak. “We see this massive ice cap growth in North America… We see the tropical rain belts in the western Pacific shifting dramatically at this point, and then also the wind belts in the southern ocean and a drying out in Australia,” says Turney.
The researchers also applied a model to examine how the atmosphere’s chemistry might improve if the Earth’s magnetic field decreased. There was an extended period of low solar activity, which would have further reduced Earth’s protection against cosmic radiation.
Analyzes of ice cores suggest that such declines in solar activity, known as “great solar minima”, coincided with the Laschamps excursion. The results reveal that changes in the atmosphere could have resulted in considerable changes in climate, thunderstorms and extensive coloured auroras.
Apart from the environmental changes that could accelerate ice caps’ growth and contribute to the extinction of Australian megafauna, the team suggests that they could also be linked to the emergence of handprints with ocher. Red assumes that humans may have used the pigment as a sunscreen against the increased ultraviolet radiation levels hitting the Earth due to ozone depletion.
They also suggest that the increase in the use of caves by our ancestors during this time and the rise of rock art may be due to the underground spaces providing shelter from harsh conditions. The situation may have also fueled competition, potentially contributing to the end of Neanderthals.
Earth’s magnetic field has decreased by about 9% over the past 170 years, and researchers say another reversal could be considered. Richard Horne, head of space, weather, and atmosphere at the British Antarctic Survey, said the study matched the chemical changes in the upper atmosphere predicted by the survey. It is what had been measured at the Halley research station in Antarctica during intense but short-lived events in which energetic particles were emitted from the Sun.
However, Anders Svensson of the University of Copenhagen says ice cores from Greenland and Antarctica show no evidence of dramatic climate change around the Laschamps excursion time, but it does. not rule out that this had an impact. “The changes in the ozone layer and the impact of increased UV radiation on humans is not something we can confirm or reject from ice cores.”
Chris Stringer, who studies human origins at the Natural History Museum in London, says the work was necessary. He clarifies that the increased use of caves as shelters is plausible but that the link with an increase in rock art is less convincing, as paintings of pigs were produced in Sulawesi, Indonesia, long before the excursion Laschamps.
“The authors also make a connection to the physical extinction of Neanderthals around 40,000 years ago, and I think that certainly could have contributed to their demise. But they have survived longer and spread more widely than Europe alone, and we have a terrible idea of when they finally disappeared in parts of Asia,” Stringe concludes.