The Best Australian Essays 2015

by Geordie Williamson

  He calls the photosynthetic process ‘almost magical’. His description gives a flavour of the magic involved: ‘When one, very specific chlorophyll molecule embedded in a reaction center absorbs the energy from a photon, the energy of the light particle can push an electron off the chlorophyll molecule. For about a billionth of a second, the chlorophyll molecule becomes positively charged.’ The electron ‘hole’ in the chlorophyll molecule is in turn filled by an electron from ‘a quartet of manganese [the chemical element] atoms held in a special arrangement on one side of a membrane’. The electron ‘hole’ thus formed in the manganese quartet is filled with electrons from a water molecule. This causes the water molecule to fall apart, creating free oxygen.

  Photosynthesis permits a local and temporary reversal of the second law of thermodynamics – the creation of order out of disorder. Magical indeed, but in early 2014 photosynthesis was revealed to be even more magical than Falkowski’s book allows. Physicists based in the United Kingdom demonstrated that quantum mechanics plays a vital part in the photosynthetic process, by helping to transport the energy it captures efficiently, in a wavelike manner.1

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  If chemistry is not your cup of tea, Falkowski offers an alternative way of thinking about how photosynthesis works – as a microscopic sound and light show. The light is of course the photon that energises the performance, while the sound is provided by the chlorophyll molecule, which flexes with an audible ‘pop’ when it loses its electron. The phenomenon was discovered by Alexander Graham Bell, who in 1880 used what he called the ‘photoacoustic effect’ to make a device he named the photophone. Bell used the photophone to transmit a wireless voice telephone message 700 feet, and considered it to be his greatest invention. And perhaps it was, since it was the precursor of fibre optic communication.

  The way that the sophisticated nanomachines Falkowski describes became incorporated into a single complex cell, such as those our bodies consist of, is so incredible that it reads like a fairytale. Using a system known as ‘quorum sensing’, microbes can communicate, and they use this ability to switch on and off various functions within their own populations and within ecosystems composed of different microbe species. Quorum sensing can even operate when one microbe swallows another, as happened over a billion years ago when a larger cell began to communicate with a smaller one that it had ingested. Quorum sensing permitted the potential food item to live inside its host instead of being digested. Then it allowed genes to switch on and off in ways that benefited the new chimeric, or genetically mixed, entity. The two genomes co-existing in the chimera even managed to exchange some genes, further enabling it to operate as a competent whole. As a result of these changes, the organism that was swallowed was transformed into a mitochondria, and began supplying ATP to the first eukaryotic cell – that is, a cell containing a nucleus and other complicated structures.

  As impossible as this process sounds, it was followed by an even more outlandish occurrence. Somehow the newly created binary organism swallowed yet another entity – a kind of bacteria that could photosynthesise. Again the ingested entity lived on inside the cell, using quorum sensing to somehow synchronise its ‘almost magical’ nanomachinery with those of the binary organism. This newly constituted ‘trinity organism’ became the photosynthetic ancestor of every plant on earth.

  Microbes control the Earth, Falkowski tells us. They created it in its present form, and maintain it in its current state by creating a global electron marketplace that we call the biosphere. Falkowski argues that we can conceive of our world as a great, unitary electrical device, driven by the myriad tiny electric motors and the other electrochemical nanomachinery of cells. Viewing the world this way reveals hitherto unappreciated dangers in some modern science.

  Some molecular biologists are doing research on ways of inserting genes into microorganisms in order to create new kinds of life that have never previously existed. Others are busy working out whether the cellular nanomachinery itself might be improved. Falkowski recommends that ‘rather than tinker with organisms that we can’t reverse engineer, a much better use of our intellectual abilities and technological capabilities would be to better understand how the core nanomachines evolved and how these machines spread across the planet to become the engines of life.’

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  Just how far we are from obtaining an understanding of the evolution of the nanomachines is conveyed in Peter Ward and Joe Kirschvink’s latest book, A New History of Life. Both authors are iconoclasts, and their book is at times breathtakingly unorthodox. Yet their ideas are at the cutting edge of many debates about the evolution of life, making their book challenging and rewarding. The work of the paleontologist is like that of a restorer of ancient mosaics: the further we go back in time, the fewer tesserae, or mosaic components, we have. Those seeking to understand the origin of the nanomachines have to work with the equivalent of just half a dozen pieces from a picture comprising tens of thousands. Time and our restless Earth have destroyed the remainder. Despite this awesome handicap, Ward and Kirschvink are convinced that, owing to the new technologies, we are at last asking the right questions.

  We have a reasonably concise date for the formation of Earth – 4560 million years ago, give or take 10 million years. The half a billion years that followed, known as the Hadean Eon, were momentous. A huge asteroid slammed into the planet, forming the moon and transforming Earth into a ball of molten rock. As Earth cooled, the progenitors of the modern core and crust were formed. Earth’s oldest rocks – tiny, 4.4-billion-year-old zircon crystals from Western Australia – are the only physical evidence we have of this period. Chemical analysis reveals that they formed where ocean water was being sucked down into the mantle – the layer of the earth between the crust and the core. So we can surmise that Earth cooled quickly after the asteroid collision, and that at an early stage it had oceans.

  Despite the presence of oceans, Earth was almost certainly hostile to life in the Hadean Eon. Asteroid impacts repeatedly shook the planet, boiling its oceans and changing the atmosphere. But by four billion years ago, things had begun to settle down. The 1.5-billion-year-long Archean Eon had begun, and it was over the first third of this period that the nanomachines either evolved or, as Ward and Kirschvink argue, colonised Earth from elsewhere.

  As we ponder life’s origins, Ward and Kirschvink warn against thinking in simplistic terms like life and death, instead encouraging us to consider the ‘newly discovered place in between’. Life’s most distant origins lie in the nonliving precursor molecules for RNA, organic compounds known as amino acids. They have been found in meteorites, are presumed to be widespread in the universe, and their origins must greatly predate Earth’s origins. The nanomachines possess attributes of life, and when brought together in a cell they clearly cross the threshold into the self-regulating, replicating entity that we recognise as a living thing.

  A slick layer of graphite preserved in 3.8-billion-year-old rocks near Isua, Greenland, was long believed to contain the earliest evidence of life on Earth. But recent studies reveal that the carbon composing the graphite was not formed by life at all. The next oldest evidence was long thought to be 3.5-billion-year-old microscopic fossils of algae from Western Australia. But recent research has shown that the ‘fossils’ are far more recent, and in any case may not be fossils at all, but crystals. A 2012 study announced that fossils of bacterial ecosystems dating back 3.49 billion years had been discovered in the Pilbara region of Western Australia, and this is now widely accepted as the oldest evidence of life.2

  Charles Darwin famously speculated that life began in a ‘shallow, sun-warmed pond’. But back when Earth formed, its surface was probably covered entirely, or almost so, by oceans. And because Earth lacked an ozone layer for the first 2 billion years of its existence, it is unlikely that shallow waters could have hosted life’s origin because ultraviolet radiation would have torn apart the delicate, assembling RNA.

  Currently favoured candidates for a
n earthly origin of life range from hot springs to mid-ocean ridge vents known as ‘black smokers’. Conditions there may have aided the formation of the ever-longer strings of amino acids and molecules, including RNA, that were eventually able to metabolise and reproduce. Mid-oceanic ridges are protected from ultraviolet radiation by the overlying ocean. They are also rich in the elements required for DNA. Additionally, the majority of the most ancient life forms on Earth are thermophiles, small organisms some of which thrive in near-boiling water. One problem for this theory is that water attacks and breaks up the nucleic acid polymers that make up RNA. And unless protected, it is also destabilised by heat.

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  Most research focuses on a search for the earliest life. But perhaps we should be searching instead for evidence of the first nanomachines. Chemical signatures in rocks that result from the activities of the nanomachines offer one means of doing this. For example, studies show that the nanomachines that make atmospheric nitrogen, and can add oxygen to the ammonia so produced in order to create nitrate, were in existence by at least 2.5 billion years ago.3

  Joe Kirschvink argues that Earth’s rocks are the wrong place to look for the nanomachines’ origins. He is a leading proponent of the seemingly radical theory that the nanomachines, and perhaps life itself, originated on the ice caps and glaciers of ancient Mars. The case is fleshed out fully in A New History of Life, and recent discoveries are building an impressive body of supporting evidence. NASA’s Curiosity lander, for example, has found evidence for ancient Martian streams and ponds: billions of years ago Mars probably had an ocean, as well as land and ice caps. The red planet may have offered a far less hostile environment for assembling naked strings of RNA than Earth. Kirschvink also points out that space travel by early life is not improbable. Mars is small, so its gravity is weak compared with that of Earth. Asteroids could therefore have thrown up a lot of rocks capable of escaping Martian gravity. And we know, through experiments, that meteorites originating from Mars can reach Earth without being sterilised.

  But if the nanomachines did originate on Mars, where might they have crossed the ‘Darwinian threshold’ and become truly living things? Kirschvink argues that Earth’s atmosphere offers a plausible nursery. Held aloft by fierce winds and currents, the Martian RNA fragments may have mixed with each other, exchanging fragments from one chain to another. Natural selection would have favoured the more functionally complex and efficient strands, which would then have proliferated. Eventually, perhaps when the strands became encompassed by cell walls made of tiny droplets of lipids (a type of molecule that includes fats and waxes), the mass transfer of genes between the nascent nanomachines slowed and their chemistry stabilised.

  The Nobel laureate Christian de Duve believed that at this point life would have emerged from nonlife very quickly, perhaps in minutes. 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 help us begin to see where the next big questions about life’s origins lie, and how they might be investigated.

  Notes

  1. See Jon Cartwright, ‘Quantized Vibrations Are Essential to Photosynthesis, Say Physicists’, physicsworld.com, 22 January 2014.

  2. See Nora Noffke, Daniel Christian, David Wacey and Robert M. Hazan, ‘A Microbial Ecosystem in an Ancient Sabkha of the 3.49 GA Pilbara, Western Australia, and Comparison with Mesoarchean, Neoproterozoic and Phanerozoic Examples’, GSA Annual Meeting, November 2012.

  3. See ‘Billions of Years Ago, Microbes Were Key in Developing Modern Nitrogen Cycle’, (e) Science News, 19 February 2009.

  New York Review of Books

  Belsen: Mapping the Memories

  Nadia Wheatley

  I vividly remember my reaction when I discovered that my father had worked at Belsen.

  This revelation came in 1983, a few weeks after his death, when his widow sent me an old press clipping, together with a note saying she’d found it among his papers and she supposed I had better have it. Feeling as if I should handle it with tongs (and not just because the paper was brittle with age), I picked it up. Dated 22 February 1947, it was from the newspaper in my father’s hometown in northern England, and was typical of a small-town newspaper piece.

  Titled ‘Hexham Man’s New Post in Germany’, the article explained that Colonel J.N. Wheatley had recently been appointed chief medical officer for the United Nations Relief and Rehabilitation Administration (UNRRA) in the British Zone, where he would have overall responsibility for some 280,000 Disp
laced Persons (DPs) living in makeshift camps. As I skimmed through the account of the work he had been doing in Germany for the two years prior to this appointment, I found myself coming to a dead halt at the information that ‘Colonel Wheatley was medical superintendent of the Belsen camp hospital’.

  Belsen! Although I was aware that this must have been after the time when it was a Nazi concentration camp, nevertheless the very name made my blood run cold. Simultaneously there came into my mind’s eye a photograph (or was it a moving image I had seen in some documentary film?) of naked corpses – already looking like skeletons – being bulldozed into the pit of a mass grave. A few moments later, still holding the page of newsprint, I was astonished to be feeling an unaccustomed benevolence towards my father, even a sense of dawning comprehension. Ah, so this was why the man was so difficult, so cold! Did it even explain his habit of whistling through his teeth – a single monotone note, more of a hiss really than a whistle – as he blocked out everyone and everything around him? And indeed, did whatever my father had experienced at Belsen explain, if not excuse, his treatment of me, and of my mother?

  *

  As reality set in, memories began to flow. While my father’s connection with Belsen was completely new to me, the fact that both my parents had worked for UNRRA in post-war Germany had been a part of my knowledge even before I could print the alphabet letters that made up the acronym of the world’s first international aid agency. Indeed, one of my first picture books was an album containing the photos of the strange-looking people who were my parents’ friends and colleagues from that period, as they gathered in June 1948 to celebrate the marriage that had taken place earlier that day at the British Consulate in Hamburg; a bare ten months later, my mother gave birth to me in Sydney. Although I never knew even the names of the wedding guests, the DPs with whom my mother and father had been working in Germany were to me real flesh and blood, because through the first six years of my life a steady stream of people whom my parents had known in various camps came to live in the flat that was attached to the side of our house. Forbidden to bother them, I paid my visits in secret, and as I lay in bed at night the sound of voices talking and singing in Polish used to come through my nursery wall with its Beatrix Potter frieze; sometimes, too, there was the sound of crying.