Not continental drift, not oxygen shifts. These open up the door, but something else has to push it.-http://phys.org/news/2014-10-oxygen-percent-today-roughly-billion.html-OOL researchers love to push reasons like this for the appearance of life and of evolutionary progress. Factors yet, but O2 only allows for progress, but doesn't create the progress. Science writers are close to worthless in descrimination.