Some fields of science are so wide open, such virgin swamps of unexplored territory, that it takes some radically divergent approaches to make any headway. There will always be opinionated, strong-minded investigators who charge in deeply and narrowly, committed to their pet theories, and there will also be others who consolidate information and try to synthesize the variety of approaches taken. There are dead ends and areas of solid progress, and there is much flailing about until the promising leads are discovered.
Origins of life research is such an unsettled frontier. I wouldn’t want to work there, but the uncertainty and the confusion and the various small victories and the romance of the work do make for a very good story. And now you can read that story in Robert Hazen’s Gen•e•sis: The Scientific Quest for Life’s Origins (amzn/b&n/abe/pwll).
Now I am not a geologist, a chemist, or a geochemist, and most of this book is written from the perspectives of those disciplines. I’ve been interested in abiogenesis for a long time, but I’ve always approached it as a biologist, assuming that the best way to attack the problem was to start with life and extrapolate backwards, moving from the complex to the simpler. Gen•e•sis turns that around, though, and most of the focus is on prebiotic chemistry—how the earth acquired a collection of organic precursors that would form the building blocks of life. I can assure you, at least, that since my prior understanding of this stuff was just about nil, even the most technical parts of this book are approachable by the lay reader.
One thing, though, that you will not find in the book is The Answer. Hazen is forthright in summarizing the difficulties in the various theories and explaining that our knowledge is very sketchy. He also exhibits the virtues of a real scientists faced with an intractable problem: at the same time that he’s explaining that some crucial piece of the puzzle is missing, he’ll outline a positive research program to find and test that part of the story (strangely, though, that program never involves emphasizing the existence of a controversy or legislating a program of instruction in the high schools…). For example, one model for the origin of life is that metabolism, in particular some analog of the citric acid cycle, arose first. This model has a major flaw, though, in that no one has found a pathway that generates one crucial molecule, oxaloacetate, under plausible prebiotic conditions. Does that mean the model is to be discarded? No, it means there is a specific line of research that needs to be pursued first, and he proposes experiments using an environment rich in hydrogen sulfide that might bridge the gap.
That’s another strength of the book: it is written by a practicing scientist, and describes how researchers in this field are doing their work. If you’ve been curious about how people can do experiments that address conditions 4 billion years ago, you’ll find examples here.
He also covers some of the major personalities—Stanley Miller, Sydney Fox, Bill Schopf, Günter Wächtershäuser (man, how can you argue with a three-umlaut scientist?), and Jack Szostak, for instance—and their ideas and how they relate to one another. Hazen’s got his own biases in how things happened and he isn’t reticent about sharing them, but still, he manages to be extraordinarily even-handed and complimentary to his competitors and colleagues.
If there is a weakness to the book, it is that it is focused so strongly on the pre-biotic world. While it does have a short discussion of the RNA world hypothesis, how early biology would have worked is not an emphasis—once cell-like precursors start maintaining a self-sustaining metabolism and replicating, well, we’re going to find another book to discuss that. Gen•e•sis is very specifically about the subject in the title: how did a dead world, warm and wet and rich in minerals and gasses, spawn a chemistry that led to the complex early replicators?
It’s a book that describes research into early origins, so while I’ve already said that Hazen won’t try to give The Answer, he does propose Some Answers, so I’ll at least mention the three models he proposes. These aren’t complete, of course, but it’ll give you an idea of the directions the results are taking.
- Life began with metabolism, and genetic molecules were incorporated later. Wächtershäuser is a key figure here, and I’d also mention Stu Kauffman. The idea is that you could have sloppy replication (actually, simple growth) of a chemical environment, and informational macromolecules would be a later refinement that made the process more robust and reliable.
- Life began with self-replicating genetic molecules, and metabolism was incorporated later. This idea hypothesizes that the first molecules of life were complex polymers that were launched into cycles of Darwinian competition, and the elaborations of metabolism were later features that accumulated, conferring greater fitness on the possessors.
- Life began as a cooperative chemical phenomenon arising between metabolism and genetics. This is a kind of best of both worlds compromise, but hey, why not? It’s a big planet, and one of the things that you learn in this book is that there are many ways that complex molecules are generated spontaneously. I have no problem with the idea that lots of chemical reactions were taking many different directions, and that the origin of life was a “you got chocolate in my peanut butter/you got peanut butter in my chocolate” moment.
Gen•e•sis is readable, entertaining, and informative, and it doesn’t stint on the satisfyingly pragmatic details of the process by which this wide-open field of research is done. If you’ve ever wondered what was going on in the first 10-100 million years of the Earth’s history after the planet had cooled down, this book will give you some ideas.