This is the Stairway of Biohistory. It depicts the 3.8 billion year history of living organisms as viewed from the two aspects of increasing diversity (as you go up) and universality (as you go down).
As you step up and down the stairs looking at the 56 mural illustrations (artist: Utako Kikutani) of major biohistorical developments hung on the wall, you can experience the history beginning with the very first cell. We look at one. We climb further. We look at another. And continue onward, tracing the history of living organisms as we do. Through it all, we encounter the recurring themes of expanse (diversity) and connectiveness (universality).“Consider each step to correspond to roughly 100 million years.