Read Online The Best Australian Essays 2015 by Geordie Williamson - Free Book Online

Safe behind its lipid cell walls, the RNA could enter the ocean, finding the rich trove of nutrients that exists around the black smokers. From then on, Darwinian evolution would have ensured the survival of those that operated most efficiently in a hot environment. This story is, of course, almost entirely unsupported by evidence. It is a scenario – a vision of how things might have been – rather than a fleshed-out scientific theory. It is nonetheless useful because it provides a target for future researchers.
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    A New History of Life deals with life’s entire trajectory, from the time before its first spark to the present. The conventional view is that for a billion years after life first evolved, very little seems to have happened. Then, over perhaps a few hundred million years, oxygen utterly transformed the face of Earth. That oxygen came from the most complex cellular nanomachinery ever to evolve – the trinity organisms, composed of three organisms embedded within a single cell, that could photosynthesise. But Falkowski’s nanomachines make me think that the billion-year ‘pause’ before their emergence is illusory. Enormous changes to life’s engines occurred as they transformed from relatively simple nanomachines to planet-altering photosynthesisers.
    A mystery surrounds the oxygenation of Earth. The oxygen produced by the photosynthesisers should have interacted immediately with organic matter, preventing any increases in free atmospheric oxygen. And indeed this is what appears to have happened for hundreds of millions of years after the first trinity organisms evolved. What was needed, if free oxygen was to accumulate in the atmosphere, was for some of the organic matter it reacted with to be put out of the oxygen’s reach.
    Falkowski thinks that ‘the oxygenation of Earth had much to do with chance and contingencies’. Ward and Kirschvink agree, saying that one of the greatest contingencies was the creation of what we call fossil fuels. For fossil fuels and other buried organic molecules are organic matter put out of oxygen’s reach many millions of years ago, and they exist in Earth’s crust in direct proportion to the amount of oxygen in the atmosphere.
    The dependence of evolutionary change on contingencies is further highlighted when Ward and Kirschvink discuss the evolution of the first large animals. They arose about half a billion years ago, in what is known as the Cambrian explosion. Scientists have long argued about why they evolved so rapidly, and at that time. Ward and Kirschvink think they have an answer, in the form of ‘true polar wander’. Essentially, the idea is that as the continents moved over the face of the planet, they altered its centre of gravity. By around half a billion years ago they had so shifted the gravitational centre that the Earth’s outer layers had begun to move relative to Earth’s core. Over millions of years, the landmasses originally lying over the poles came to lie over the equator. This southward shift may have released methane trapped in clathrates (ice-methane combinations kept stable by low temperatures or pressure), triggering a release of greenhouse gases that warmed the climate and provided favourable conditions for an increase in biodiversity. There is evidence to back parts of this theory. Something odd was happening to Earth’s poles around the time complex life evolved. And ‘true polar wander’ is characteristic of other planets, including Mars. But again, Ward and Kirschvink are pushing the envelope with this theory.
    Neither Life’s Engines nor A New History of Life is an easy book for the non-scientist, but both are immensely rewarding. Like Galileo’s telescope and microscope, they focus on the very small (Falkowski) and the very big picture (Ward and Kirschvink). Both are full of novel thinking about life’s origin and subsequent evolution. Taken together, they