I heard an interesting report on “Science Friday” today, maybe you might like to comment on it…
Some new research in paleomagnetism has come up that suggests the Earth’s magnetic field, after a long period of decline, suddenly became much stronger about 500 million years ago. This strengthening has been attributed to the formation of earth’s solid core, which supposedly occurred around that time. Apparently, this new configuration of the iron core has led to a much stronger terrestrial magnetic field, and all that implies (improved protection from cosmic radiation).
The association with the Cambrian Explosion, which also occurred about that same time, immediately came to my mind, and the geophysicist being interviewed also mentioned that there might be a connection between these two events, although he admitted that there was no direct evidence of such. Still, a sudden reduction in radiation at Earth’s surface might very well have an influence on the sudden evolution of multicellular life-forms, and might very well explain their sudden rise at that time.
As you know, prior to the Cambrian Explosion a half-billion years ago, all life on Earth lived in the sea, and was microbial in nature. After three billion years of evolution, the most complex biological organisms seemed to have been stromatolites, which are not true metazoans, but loosely organized colonies of algae and other single-celled creatures, not even as highly evolved as a sponge. After the CE, all the major phyla of advanced life (and many others which have since gone extinct) suddenly appeared and flourished). Not only was the change profound, it was sudden. It is tempting to think the two events were connected.