Evolution is just a theory, and there's no solid evidence to support it. It's more likely that these changes in the magnetic field were caused by natural fluctuations, not some grand evolutionary process.
“Collapse of Earth′s magnetic field may have fueled evolution of life 600 million years ago - Livescience.com”
“Collapse of Earth′s magnetic field may have fueled evolution of life 600 million years ago - Livescience.com”