Mar 17, 2025 04:27 PM
https://pubs.aip.org/physicstoday/online...s-and-life
EXCERPT: . . . Geophysicists and mineral physicists are approaching a consensus that could provide the key conceptual framework—the weak-field state before inner-core nucleation —to understand why the Ediacaran geomagnetic field was so strange. Huang and colleagues also found a striking correlation between the evolutionary radiation (rapid increase in speciation) of animal life and the ultraweak field, and they took up anew the question of linkages with evolution.
Joseph Meert and colleagues had in 2016 suggested that a weaker field, which they inferred might be present from the apparent frequent geomagnetic reversals, was related to the explosion of complex life during the Cambrian Period, when nearly all modern animal phyla first appeared in the fossil record. (Although the Cambrian explosion of life has been recognized since the mid 20th century, the Avalon explosion of the preceding Ediacaran Period was discovered only in recent decades.)
In Meert and colleagues’ model, a key agent driving the Cambrian explosion was a greater incidence of energetic solar protons. Charles Jackman and colleagues had long advocated that a deeper penetration of energetic solar particles into the atmosphere during periods of weak geomagnetic field strength would lead to chemical reactions that produce nitrogen oxides, which in turn would deplete the ozone layer and lead to an increase in UV radiation. Meert and colleagues hypothesized that a higher UV-B flux would increase mutation rates and thereby stimulate evolutionary processes during the Cambrian.
But Manasvi Lingam questioned the linkage because the atmosphere and water shield much UV radiation, something Carl Sagan had highlighted some 60 years earlier. Paleontologists infer that most new Ediacaran and Cambrian animal forms lived in the subsurface of oceans, which makes UV shielding particularly relevant. And Huang and colleagues emphasize that the correlation between the ultraweak field and evolution is a phenomenon of the Ediacaran Period and not the Cambrian Period.
Paleontologists have documented that eukaryotes (organisms with cell nuclei) were present before the Ediacaran Period, but they were almost exclusively microscopic in size. A dramatic increase in body size, however, occurred late in the Ediacaran Period—when mobile animals like the pancake-shaped Dickinsonia reached many decimeters in size—and squarely within the time of ultraweak fields. Biologists generally associate larger body sizes and increased mobility with higher oxygen demands.
Is there evidence for increases in oxygenation during that spurt of evolution? Notwithstanding considerable ongoing debate associated with the difficulty of obtaining global oxygen signatures from measurements of ancient rocks, geochemists have found a wealth of data supporting an increase in oxygenation that coincides with the ultralow geomagnetic fields as shown in figure 4. Faced with a correlation between the ultraweak fields, oxygenation, and animal radiation, my group at the University of Rochester then asked the question, What might link these phenomena? (MORE - missing details)
EXCERPT: . . . Geophysicists and mineral physicists are approaching a consensus that could provide the key conceptual framework—the weak-field state before inner-core nucleation —to understand why the Ediacaran geomagnetic field was so strange. Huang and colleagues also found a striking correlation between the evolutionary radiation (rapid increase in speciation) of animal life and the ultraweak field, and they took up anew the question of linkages with evolution.
Joseph Meert and colleagues had in 2016 suggested that a weaker field, which they inferred might be present from the apparent frequent geomagnetic reversals, was related to the explosion of complex life during the Cambrian Period, when nearly all modern animal phyla first appeared in the fossil record. (Although the Cambrian explosion of life has been recognized since the mid 20th century, the Avalon explosion of the preceding Ediacaran Period was discovered only in recent decades.)
In Meert and colleagues’ model, a key agent driving the Cambrian explosion was a greater incidence of energetic solar protons. Charles Jackman and colleagues had long advocated that a deeper penetration of energetic solar particles into the atmosphere during periods of weak geomagnetic field strength would lead to chemical reactions that produce nitrogen oxides, which in turn would deplete the ozone layer and lead to an increase in UV radiation. Meert and colleagues hypothesized that a higher UV-B flux would increase mutation rates and thereby stimulate evolutionary processes during the Cambrian.
But Manasvi Lingam questioned the linkage because the atmosphere and water shield much UV radiation, something Carl Sagan had highlighted some 60 years earlier. Paleontologists infer that most new Ediacaran and Cambrian animal forms lived in the subsurface of oceans, which makes UV shielding particularly relevant. And Huang and colleagues emphasize that the correlation between the ultraweak field and evolution is a phenomenon of the Ediacaran Period and not the Cambrian Period.
Paleontologists have documented that eukaryotes (organisms with cell nuclei) were present before the Ediacaran Period, but they were almost exclusively microscopic in size. A dramatic increase in body size, however, occurred late in the Ediacaran Period—when mobile animals like the pancake-shaped Dickinsonia reached many decimeters in size—and squarely within the time of ultraweak fields. Biologists generally associate larger body sizes and increased mobility with higher oxygen demands.
Is there evidence for increases in oxygenation during that spurt of evolution? Notwithstanding considerable ongoing debate associated with the difficulty of obtaining global oxygen signatures from measurements of ancient rocks, geochemists have found a wealth of data supporting an increase in oxygenation that coincides with the ultralow geomagnetic fields as shown in figure 4. Faced with a correlation between the ultraweak fields, oxygenation, and animal radiation, my group at the University of Rochester then asked the question, What might link these phenomena? (MORE - missing details)