Chapter 4 - Shaping Evolution

Chapter 4
        Through a glass darkly. The layers of the Earth hold traces of five hundred million years of evolution, hard body parts turned to stone and crystal as if by a magician’s spell. A drill or shovel is a time machine, although a tumult of geological change and erosion inverts some strata and eradicates others. In every conceivable niche, the Earth is vibrantly, opulently alive.
        Evolution starts with the birth of the Earth in a swirling cloud of gas and dust. In a process that lasts no more than the blink of a cosmic eye, the tiny particles collide and then stick; smoke grows into dust bunnies and rocky snowflakes. In a crescendo of accretion, molehills grow into mountains and then planets. The primeval Earth would have seemed like an antechamber to hell, with widespread volcanism and oceans barely condensed from steam. Comets and meteors slam into the surface. They set the stage for biology: carrying water from the outer solar system and phosphorus to make that energizing molecule ATP. They also bring mayhem: from time to time the Earth sweeps through a hail of death from comet debris and the big impacts can destroy continents and ecosystems. Dying stars can be seen in daylight and they are also Vishnu, providing the heavy elements needed for life, but irradiating life until its defenses are weakened.
        Celestial ephemera speak to a contingency in evolution. Fitness is pyrrhic when nature rolls the dice and the strong die. On the other hand, life finds common solutions to the problem of survival on a fickle planet; eyes and wings and feathers have arisen multiple times in dispersed branches of the tree of life. Organisms don’t always get large and complex; the dominion of anaerobic bacteria is without parallel, yet millions could fit on the dot at the end of this sentence. Below, see the scene in the Earth’s Cambrian oceans. The planet has eased out of its snowball phase, and after three billion years of being invisibly small, life is burgeoning in the oceans.

About the Artist


Heather Green is a graduate student in the College of Fine Arts at the University of Arizona and a second generation Tucsonan. Her current work is informed by her lifelong relationship with the headland of La Cholla near Puerto Peñasco, Mexico, a passion for old science books, and her love of the natural world. She has designed exhibits about sustainable fisheries and materials for conservation initiatives, and is currently developing a virtual museum about La Cholla.

Chapter 4

Shaping Evolution

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