The integral theme is that there is an association between biological and geographical history.  Some of the oldest known fossils on Earth are the 3.4 billion year-old bacteria trapped in the Fig Tree Chert on the African continent.  The Chert is a rock structure; however, in Australia there are 3.5 billion year-old rocks called stromatolites that harbor former spherical and filamentous prokaryotes.  A stromatolite is formed by sediments coating bacterial colonies forming a layer, then the motile bacteria move on top of the layer and continually repeat this cycle to form a porous pillar of rock.  Note:  the fossilized remnants of prokaryotes in Australia appear to indicate that they were photosynthetic.

Next:  "Testing the Theories."