Cracked Open and Knit Together by Oxygen
The happy insight that biology and geology meet through chemistry has been seen throughout this book when life and rocks interact. A chemical called water transformed this planet’s rocks and opened them to give life its elemental building blocks. The energy in the Earth became the energy in simple cells through chemical wheels. Sunlight split the water with the help of dissolved rocks, and the oxygen from that reaction brought yet more elements out of the rocks and into life. That insight addresses a long-standing mystery here. Long ago, the biggest biological change in the history of the planet created plant and animal life. What caused the seas to teem with weird new life? I think the periodic table connects that biological event to a previous global geological change. If so, then once again, chemical reactions opened up geology to provide new possibilities for biological complexity. Chemistry shaped the flow of geology and biology at once. The evidence for this connection is like something that happened with the ekko sculpture in northwest Scotland from Chapter 2 (Figure 2.1). After the sculpture had been built, an archaeologist dropped by and found incisions in ekko’s rocks. The archaeologist read the shape and depth of the incisions and concluded that the stones were older than everyone thought, and must have been used for a structure now lost. Like in ekko, there are “incisions” on the Earth made by massive geological processes. Geologists have read these and have concluded that a worldwide event altered the planet’s surface. This geological event was also a chemical event. Soon after, a profusion of fossils filled the rocks. This biological event was also a chemical event. The common denominator of chemistry connects the geology to the biology. The geological event provided chemicals that life used in new ways: especially oxygen, phosphorous, and calcium, resulting in new energy, shells, and signals for life. This hypothesis is that chemical availability drove the evolution of life, and that the periodic table shaped the timing of life’s greatest expansion.