13) Earth sees herself

Selenopeltis, a Moroccan trilobite. Image license: Flickr Creative Commons

600 million years ago, light sensitive eyespots evolve into eyesight, perhaps in an ancestor of the trilobite. The Earth sees herself for the first time. Previously only soft-bodied animals evolve in the oceans. Over the next 70 million years, previously naked prey animals protect themselves with shells of calcium. Jaws, beaks, and skeletons follow suit.