The discovery of blocks of gravel which sank to the bottom of the sea trapped in ancient icebergs has sparked a new understanding of a bizarre group of creatures. The research, published in the Australian Journal of Earth Sciences, has also forced a rethink of the conditions that existed more than 500 million years ago. 580 million years ago, the ancient oceans were flooded with enough oxygen that the way in which life was constructed was completely changed. This moment was the birth of multi-cellular organisms, and shortly preceded the burst of biological diversification called the Cambrian explosion. Recent evidence indicates that this was the last in a series of similar increases in oxygen availability that changed the world’s climate and ecological conditions.