According to the researchers, the change in the Earth's magnetic poles, along with the fall in solar activity 42,000 years ago, could create an apocalyptic environment that may have played a role in major events from the extinction of the megafauna to the death of the Neanderthals.
The Earth's magnetic field acts as a shield against destructive cosmic radiation, but when the poles are swapped, as has happened many times in the past, the shield weakens dramatically and leaves the planet vulnerable to high-energy particles.
One temporary pole shift, known as the Lashamp excursion, occurred 42,000 years ago and lasted about 1,000 years. According to the researchers, there was little evidence in previous work that the event had a profound impact on the planet, perhaps because the focus there was no period during which the poles were actually shifting.
Scientists now say that this change, together with a period of low solar activity, could be responsible for a huge number of climatic and environmental events with dramatic consequences.
"It probably could seem like the end of days," said Professor Chris Turney of the University of New South Wales and co-author of the study.
The team called this period "the Adams event," a nod to Douglas Adams, author of The Hitchhiker's Guide to the Galaxy, in which 42 was said to be "the answer to the ultimate question about life, the universe and everything else." …
In an article in the journal Science, Turney and colleagues describe how they performed radiocarbon analysis of rings of ancient cowrie trees preserved in the northern wetlands of New Zealand, some of which are more than 42,000 years old.
This allowed them to track the increase in carbon-14 levels in the atmosphere over time, caused by the increased levels of high-energy cosmic radiation reaching Earth during their tour of Lashamp. As a result, they were able to date atmospheric changes in more detail than has been suggested in previous records, such as mineral deposits.
They then examined numerous records and material from around the world, including from lakes and ice cores, and found that many major environmental changes occurred concurrently with the peak of carbon-14 levels.
“We are seeing massive ice cover over North America… we are seeing the tropical rain belts in the western Pacific move abruptly at this point, followed by the wind belts in the southern ocean and drying up in Australia,” said Terney. …
The researchers also used the model to study how the chemical composition of the atmosphere might change if the Earth's magnetic field is lost and there is an extended period of low solar activity, further reducing the Earth's protection from cosmic radiation. Ice core records suggest that such drops in solar activity, known as "large solar minima," coincided with the Lashamp excursion.
The results indicate that atmospheric changes could have led to huge climate changes, thunderstorms, and widespread colorful aurora borealis.
In addition to environmental changes that potentially accelerate the growth of ice sheets and contribute to the disappearance of the Australian megafauna, the team speculates that they may also be associated with the appearance of red ocher palm prints. It is speculated that people may have used the pigment as a sunscreen against increased levels of ultraviolet radiation. falling to the Earth as a result of ozone depletion.
They also suggest that the rise in the use of caves by our ancestors around this time, as well as the rise in cave art, may be related to the fact that underground spaces served as a refuge from harsh conditions.The situation could also intensify competition, potentially contributing to the extermination of Neanderthals, Terney said.
The Earth's magnetic field has weakened by about 9% over the past 170 years, and researchers say another twist is possible. This situation could have dramatic consequences, not least due to the disruption of electrical networks and satellite networks.
Richard Horn, head of space, weather and atmosphere at the British Antarctic Survey, who was not involved, said the chemical changes in the upper atmosphere predicted by the study were in line with data measured at the Halley Research Station in Antarctica during strong but short-term events in which energetic particles were emitted by the Sun.
But could the environmental impact be as severe as the team predicts? “Maybe not so much, but it makes you think,” Horn said, noting that it is unlikely that the Earth's magnetic field will completely disappear.
Dr. Anders Svensson of the University of Copenhagen, however, said ice cores from Greenland and Antarctica show no evidence of any dramatic climate changes that occurred during the Lashamp excursion, but this does not rule out that it had an impact. “Changes in the ozone layer and the effects of increased UV radiation on humans are not something we can confirm or deny based on ice cores,” he said.
Chris Stringer, who studies human origins at the Natural History Museum in London, said the work was important. He said that the increased use of caves as a refuge was plausible, but that the link to the rise of cave art was less convincing because the paintings of pigs were apparently created in Sulawesi, Indonesia, long before the Lashamp excursion.
“The authors also associate with the physical disappearance of the Neanderthals about 40,000 years ago, and I think that this could definitely contribute to their demise. But they really survived longer and were located more widely than just Europe, and we have a very bad decision. on the timing of their final disappearance in different parts of Asia."
Dr. Richard Staff, Quaternary Geochronology Research Fellow at the University of Glasgow, said the study was exciting and could lead to further research into the ecological and evolutionary effects of other, more severe dips in the Earth's magnetic field in the more distant past. … during.