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Bioelectromagnetism

sensitivity (Channell and Vigliotti, 2019). Moreover, in this period, mammalian fossils in Australia and

Eurasia record an important die-of of other large mammals probably due to the same reason (Channell

and Vigliotti, 2019). In the case of Australia, fossil occurrences and dung-fungal proxies indicate that

episodes of the Late Quaternary extinction of mammalian megafauna occurred close to the Laschamp

and Blake excursions (Channell and Vigliotti, 2019). In addition, in the Americas and Europe, a large

mammalian die-of appears to have occurred ~13 ka (Channell and Vigliotti, 2019). Tis is because fos­

sil and dung-fungal evidence for the age of the Late Quaternary extinction coincides with a prominent

decline in the decrease in the GMF intensity (Channell and Vigliotti, 2019). Both die-ofs can be linked

to minima in the GMF strength implying that variations of UV radiation fux to the Earth’s surface

infuenced mammalian evolution (Channell and Vigliotti, 2019). For the last ~200 ka, estimates of the

timing of branching episodes in the human evolutionary tree, from modern and fossil mitochondrial

DNA and Y-chromosomes, can be linked to minima in feld strength which implies a long-term role for

UV radiation in human evolution (Channell and Vigliotti, 2019).

According to Cooper et al. (2021), the Laschamp excursion in combination with the Grand Solar

Minima initiated substantial changes in the concentration and circulation of the atmospheric ozone

and increased atmospheric ionization and UV radiation levels, leading to global climate shifs that

caused major environmental changes. It was also suggested that those environmental changes could

have sparked a chain of events leading to the extinction of large mammals in Australia and Europe, and

possibly to the extinction of Homo neanderthalensis and subsequent success of Homo sapiens (Channell

and Vigliotti, 2019; Cooper et al., 2021). Similarly, large mammals’ extinctions in North America and

Europe 13,000 years ago could be linked to geomagnetic excursions identifed in sediments of Brunhes

Chron (Erdmann et al., 2021).

More recently, Cooper et al. (2021) created a precisely dated radiocarbon record around the time of

the Laschamp excursion about 41 ka from the annual rings of ancient New Zealand giant swamp kauri

trees (Agathis australis, 42,000-year-old subfossil). Tey precisely characterized the geomagnetic transi­

tion and performed global chemistry-climate modeling and detailed radiocarbon dating of paleoenvi­

ronmental records to investigate impacts (Cooper et al., 2021). Tis geological archives record revealed

a substantial increase in the cosmogenic isotopes ¹⁴C content of the atmosphere culminating during the

period of weakening MF strength preceding the polarity switch (Cooper et al., 2021). Te radiocarbon

was supplied to the Earth by continuous GCRs, and the radiocarbon lef in the annual rings indicated

that a large amount of the radiocarbon was brought to the Earth during this period (Cooper et al., 2021).

Combined with an unusually quiet Sun, known as the “Grand Solar Minima” that is believed to have

occurred during the Laschamp excursion, a large amount of GCRs could have caused a notable drop in

stratospheric ozone, shifing wind fows and climate patterns (Cooper et al., 2021).

Te GMF at that time has been estimated to be weakened to <28% of the current strength. According

to this record, however, the GMF became the weakest about 42.2 ka before the Laschamp excursion

and its intensity was only 0%–6% of the present (Laj et al., 2014; Brown et al., 2018; Liu et al., 2020). Tis

GMF reduction resulted in more GCRs reaching the Earth, causing greater production of the cosmo­

genic isotopes ¹⁴C (Cooper et al., 2021). Tus, due to the almost disappearance of the GMF and the loss

of the “protective shield” of the Earth, charged GCRs fell unobstructed and ionized fne particles in

the Earth’s atmosphere, and the ionized atmosphere destroyed the ozone layer and synchronous global

climate change, such as glacial maxima and aridifcation, was caused (Cooper et al., 2021). Comparing

this record with that of the Laschamp excursion already measured in ice cores, etc., it coincided with the

period when ice beds and glaciers expanded in North America and the generating mechanism of wind

zones and tropical cyclones changed signifcantly (Cooper et al., 2021). During this period, the large

fauna (Megafauna) became extinct at the same time in mainland Australia and Tasmania. While the

Neanderthals became extinct (recalibrated at 40.9–40.5 ka), murals in caves suddenly appeared around

the world (Cooper et al., 2021). Cooper et al. (2021) think that it is very premature to connect this event to

milestones in human evolution that occurred around that time, such as the demise of the Neanderthals

or increase in cave painting though the link is worth investigating (Voosen, 2021).