Did Complex Life Appear Because the Magnetic Field was Weak?

Some parts of the history of the Earth's magnetic field are easy to measure. But the strength of the field is not one of them. We have lots of information of the reversals of the polarity of the field and the direction of the magnetism - think of the stripes on the ocean floor and knowing the latitude of when rocks were laid down - but the field strength of the field is harder to come by.

And this is important for the presence of the field is what protects us from deadly cosmic rays. It is very possible that no field = no life.

But some measurements of field strength have been made and one of the interesting things is that it was very low in the Ediacaran. It was a fifteenth of the present value. This and the consequences of this are discussed in THIS ARTICLE.

Did the reduction in magnetic field strength allow more genetic mutation in the single-celled creatures promoting the multi-celled Ediacaran fauna?

The article goes on to discuss the mechanism which affected the field, essentially the formation of the Earth's inner core. The 100 million years this took covers the Ediacaran and the "Cambrian Explosion".

The article gives a pleasing combination of Earth physics and biology. It may even be true!