Photosynthesis originated as a genetic mutation that allowed simple cyanobacteria to produce their own food source with only the power of the sun. However, the resulting waste product of this process, oxygen, was toxic to almost all life on the young planet. This oxygen created by cyanobacteria’s new superpower also reacted with the existing atmosphere and caused a dramatic period of cold climate known as “Snowball Earth.” When the planet emerged from this icy condition 200 million years later, the life that remained found itself in a warm, oxygen-rich environment perfect for the evolution of multicellular organisms.
