eldavojohn writes "Dr. Adam Maloof has found fossils of sea sponges in Australia from 650 million years ago. You might think this is no big deal unless you consider that sea sponges were thought to have arisen 520 million years ago. These fossils predate the oldest hard bodied fossils we have by a hundred million years. Dr. Maloof is now wondering if life might have arisen twice after the first attempt was quashed 635 million years ago: 'Since animals probably did not evolve twice, we are suddenly confronted with the question of how some relative of these reef-dwelling animals survived the Snowball Earth.' So how is it that life survived the Marinoan glaciation? The BBC has a video on the topic and Wikipedia has a time line of the Proterozoic Eon into the Paleozoic Era."