The Genesis Quest is one of those books that quickly makes a good case for its own existence. It takes the reader through the century-long research endeavour on the origin of life, providing a big-picture overview of who’s who and how their ideas have waxed and waned. Such an overview requires an outsider’s perspective on the whole show, which is exactly what science writer Michael Marshall achieves in my opinion. A superb starting point if you want to read more on this subject, this is the book I wish I had read earlier.
Judging by the long history of creation myths, the question of our origin has always fascinated us. But creation myths, contends Marshall, are not an answer. The scientific question of how life originated from non-living matter, a process known as abiogenesis, needed the theory of evolution and a conception of the age of the Earth before it was conceived of. (On a side-note, this seems to harken back to the now obsolete idea of spontaneous generation; the two are similar, but not the same.) What The Genesis Quest shows is a research community that started out unified, then splintered into competing fields, and is only recently showing signs of a reunification.
Marshall takes the 1920s as his starting point, which is when the Russian scientist Alexander Ivanovich Oparin and the British biologist J.B.S. Haldane independently theorised that life could have arisen from non-living chemicals in a step-wise fashion in Earth’s primitive oceans. Experimental support for the Oparin-Haldane hypothesis was delivered by chemists Harold Urey and Stanley Miller in the famous Miller–Urey experiment. In a laboratory setup simulating early Earth conditions, they created organic molecules such as amino acids from simple precursors. Though iconic and launching the field of prebiotic chemistry, their findings quickly became obsolete as criticism mounted. Earth’s early atmosphere was probably unlike their simulation, nor were the chemical steps observed necessarily realistic.
During the ’70s and ’80s, disagreements arose over which of life’s essential functions came first, which basic molecules came first, where on the planet this happened, and which organisms held the clues to the questions. Consequently, the field gradually splintered into four competing schools of thought that Marshall discusses in turn.
“Though each school has advanced the field, none of them have provided a complete and satisfactory solution to life’s origin”
The proteins-first school argues amino acids can spontaneously form complex proteins and even proteinoid microspheres (a sort of protocells), but it receded with the death of Sidney Walter Fox. The compartmentalisation-first school argues that life needs a container if it is not to fall apart immediately. Experiments by key figures such as David Deamer, William Hargreaves, and Pier Luigi Luisi showed how precursors can spontaneously form lipids which can then form protocells, and how they can be coaxed to divide or pick up molecules relevant to life’s biochemistry.
The other two are arguably the more widely known ideas. The replication-first school has become synonymous with the RNA World hypothesis and got boosted by discovering that RNA can have enzymatic activity (so-called ribozymes) and that it sits at the heart of ribosomes. Lastly, the metabolism-first school argues that energy underlies everything, for without a constant input to counter the second law of thermodynamics, entropy wins and life falls to pieces. This idea was boosted by the discovery of deep-sea hydrothermal vents, argued to be ideal biochemical reactors by Jack Corliss. Mike Russell predicted the existence of alkaline vents in the ’80s based on geological formations and was vindicated by the discovery of the Lost City hydrothermal field in 2000. These would provide a gentler environment and, from reviewing Alien Oceans, it is clear that alkaline vents still have currency.
Though each school has advanced the field, none of them have provided a complete and satisfactory solution to life’s origin. Experiments often fall short or have doubtful real-world relevance. This is the part of the book where Marshall finally plays his own hand and clarifies which scenario he favours based on the evidence so far. Along the way he throws out some fascinating ideas. He charts how some people have changed their minds and a new school is emerging that argues that “the essence of life is the interaction of all three” (p. 250), i.e. genes, metabolism, and a membrane-bound cell. Experiments by Jack Szostak, initially an RNA-world devotee, have partially succeeded in creating a model system with genes copying themselves inside membrane-bound protocells, though they still lack metabolism. Arguably, the boundaries between life and non-life become fuzzy once you start looking at such self-sustaining networks of chemical reactions, which is the domain of systems chemistry “The first life was so intimately bound up with its surroundings that it is difficult to tell what should count as organism and what as surroundings” (p. 272). He also highlights Harold Morowitz‘s argument that life should be considered at the level of ecosystems, or, in Marshall’s words “The first cell was not alone: it belonged to an instant community” (p. 270).
“Arguably, the boundaries between life and non-life become fuzzy once you start looking at […] self-sustaining networks of chemical reactions.”
Some people are now focusing on where such protocells would get their chemicals from, and e.g. Deamer, initially a compartmentalisation-first devotee, favours terrestrial tide pools undergoing wet-dry cycles as the best place for this. Marshall does not put much faith in hydrothermal and alkaline vents, though he does entertain the option that life might have arisen in more than one way, which opens “the possibility that several kinds of life arose in different places, and either merged or competed” (p. 278).
Marshall discusses many more researchers who made important contributions than I have space to mention here (the chapter on Graham Cairn-Smith and his notion of replicating crystals in clay stands out). This overview is arguably the book’s strongest point, but I have two additional observations. First is his eye for subtlety and detail. For example, he clarifies how speaking of the “Oparin-Haldane hypothesis” obscures the fact that their ideas differed subtly, and he explains the difference between hard and soft versions of the RNA-world thesis. Second, his version of the story of how the structure of DNA and the ribosome were discovered matches what I have read in other books.
Based on these observations I feel reasonably confident to claim that Marshall knows his stuff, even though he is “only” a science writer. I use inverted commas as I feel science journalism has a sometimes undeserved bad reputation. Here, however, having an outsider without allegiance to any research group is an advantage. The acknowledgements mention his close reporting on origin-of-life research for over a decade and 46 pages of references to journal articles back up the ideas he presents here. Clearly, Marshall has done his homework.
“This overview [of the different schools of thought] is arguably the book’s strongest point […] having an outsider without allegiance to any research group [reporting on it] is an advantage.”
Despite the serious intention, the book is very readable. He provides just the right amount of biographical information without losing focus on people’s ideas. There is the occasional footnote with nerdy pop-culture references, which is amusing when used in moderation. And he can be refreshingly brusque and honest. When introducing Haldane, he cracked me up by remarking that “Ronald Clark’s biography J.B.S. is essentially one long stream of outrageous anecdotes punctuated by occasional outbreaks of science” (p. 44) which matches the picture I got from Haldane after reviewing a more recent biography. Criticism of some of Walter Fox’s work on proteinoid microspheres is summarised as “nice experiment, but would it happen in the real world?” (p. 142). And an older Stanley Miller is described as being “very much in the ‘criticise anyone who challenges me’ phase of his career” (p. 194).
This is not the first book to give a history of this field, nor the first one written by a science journalist. Though I have not read those books, a quick comparison suggests they spend more time surveying thinking in Antiquity, which is something Marshall only briefly surveys in his first chapter. Given that I have recently been reading a fair bit about astrobiology and the origin of life, this is the book I wish I had read first. If you have any interest in delving deeper into origin-of-life research, The Genesis Quest makes a fantastic starting point that will give you the lay of the land. It gets my unreserved recommendation.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
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