The possible reason for the extinction of Neanderthals, European mammoths and other representatives of the ancient world was named by members of an international scientific group. It could be climate change on Earth, associated with the weakening of the magnetic field of our planet about 42 thousand years ago. The results of a study on modeling climate change in connection with the so-called “geomagnetic excursion” were recently published in the journal Science. The work, in which specialists from Australia, New Zealand, England, USA, Switzerland, Sweden, Germany, China and Russia took part, was supported by the Russian Science Foundation.
First, let’s clarify what determines the level of the Earth’s magnetic field and how often it decreased on our planet.
Let’s start with the most dramatic physical phenomenon – the inversion of the planet’s magnetic field. With it, the north and south magnetic poles change places, and the compass needle begins to show the opposite direction. Experts suggest that during such reversals, caused by changes in the planet’s core, the Earth’s magnetosphere weakened so much that cosmic radiation could reach the surface of our planet and cause serious harm to all living things.
Fortunately, during the existence of the species Homo sapiens (it appeared about 200 thousand years ago), not a single such inversion took place on Earth. Before us, these epochal events happened, and more than once. Presumably, the latter happened about 780 thousand years ago.
But there are also short-term changes in the Earth’s magnetic field, during which the orientation of the poles changes by only 40-45% from the previous position. It is also accompanied by a decrease in the magnetic field strength. The last and so far the only proven such shift occurred about 42 thousand years ago, at the end of the last ice age. This geomagnetic change is called the Lashamp excursion. It was recorded in the late 1960s in the lava flows of La Champs (a French village near which work was carried out). According to the residual magnetic field of ancient lava, experts found that the Earth was then protected by only 6% of the current magnetic field strength.
But what exactly changes in climate and living conditions this could lead to, scientists have found out only now. The reason to start modeling the climate that took place during the life of the Neanderthals was a new find in 2019 in New Zealand. There, experts found a fossilized cowrie tree that lived for 1700 years during the Lashamp excursion.
The chain of our reasoning about this event is built from this find, – says one of the authors of the work, Evgeny Rozanov, who led the mathematical modeling of climate, an employee of the Davos Physics and Meteorological Observatory, a graduate of St. Petersburg State University. “First, our colleagues received data on the cowrie tree ring width and composition. To these data were added data on the increase in the concentration of radiocarbon (carbon-14), which is formed in the atmosphere as a result of exposure to galactic radiation, as well as beryllium-10.
In addition, our colleagues found that, in addition to the weakening of the Earth’s magnetic field, several solar minima occurred during the described period (during which the Earth’s protection from cosmic rays decreases). These two factors have led to the fact that ionization due to galactic radiation has increased significantly on Earth.
– What contribution did the Russian side make to this study?
– We have a project dedicated to the study of extreme events in the ozone layer. We were asked to calculate the potential implications of Lashamp’s excursion. We included the degree of atmospheric ionization in our model, and performed numerical experiments taking into account various configurations of the magnetic field and solar activity. It turned out that 42 thousand years ago, there was a significant drop in ozone concentration and an increase in ultraviolet radiation, which is harmful to the skin and eyes. There was also a change in temperature and wind conditions.
– What did it lead to?
– To redistribution of temperature. Europe has become two degrees warmer, and the Atlantic Ocean has cooled.
– Could living things be hurt?
– In theory, of course, they were not comfortable. Due to climate change (where there was a blooming oasis, due to a shift in the circulation of winds, droughts began), due to an increase in radiation that could burn out the eyes. Perhaps to hide from the too strong daylight, the Neanderthals went into the caves.
The rock art of those times was found, depicting not only ancient mammoths and deer, but also a luminous sky reminiscent of auroral glow. Currently, since our magnetic field is strong enough, we can only observe such auroras in the northern regions. Then they could be observed even at the latitudes of the tropics.
– Can this phenomenon be repeated?
– We can only see what is happening at the present time and suggest a possible scenario. The north magnetic pole is now rapidly shifting from Canada towards Russia, and the south, accordingly, is moving towards it. The rate of this displacement is already reaching 50-60 kilometers per year. Whether the second “Lashamp” is awaiting us or the shift will stop, until no one can say for sure.
According to Evgeny Rozanov, there are still many questions. In particular, scientists would like to study the implications of Lashamp’s excursion into the biosphere. “Then we could establish exactly how much the climate zones shifted as a result of that ancient event. We are planning to do this research in the near future. “