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.
Thanks for the review PZ! Robert Hazen’s book sounds very interesting. Now I’ll have to buy a copy and read it for myself.
But, but, but, but, but…Goddidit! Right? Right?
Appreciate the recommendation, PZ. As a scientific layman I always want to know about good books that make current research accessible.
Sounds interesting. Maybe I can fit it in to my summer reading program (which at this point, consists almost entirely of Anthony Burgess and Salman Rushdie).
PZ, have you had the chance to take a look at Leonard Susskind’s new book? I just picked it up last week and I was naturally wondering what you’d have to say about it.
Hmm, isn’t there a sort of biological precedent for this chocolate/peanutbutter concurrence in the evolution of the first eukaryotic orgaisms? If I remember correctly, there was a sort of pre-aerobic microbe that formed a symbiotic relationship with an aerobic bacterium to cope with the rising levels of oxygen in their environment.
Günter Wächtershäuser
Gesundheit.
And lo, God did create Reese’s Peanut Butter Cups, and He looked upon His work and it was Good.
I trust they give serious consideration to my preferred theory, the Alien-Septic-Tank-Dump hypothesis.
Hey, any friend of Günter is pyrite by me.
Thanks for the review. That one is on my reading list, but I’ll have to admit that the last reccommendation I acted on (the evo-devo book whose name escapes me now… you know the one) I found interesting but somewhat impenetrable to a non-biologist. I faded out well before the midway point.
For nonscientists (myself included) interested in origin-of-life research, Astrobiology Magazine is a must-click.
Ich wuensche mir, dass ich Umlauten haette, dann waere ich echt supertoll!!!
I wish that I had umlauts, then I’d really be supercool!!!
Speaking of unfinished reading lists. I accidentally left my half read copy of Sam Harris’ ‘The End of Faith’ on a Delta puddle jumper in Salt Lake City while switching planes today on my way to Omaha. I hope some nice Mormon enjoys the free book.
Not all was lost. I finally got to crack open Dawkins ‘Climbing Mount Improbable’ on the rest of the trip. A good read so far.
Hey, I’m reading this book! Got about 75 pages into it on a flight home from Phoenix today. Quite interesting and well written. I’ve learned a great deal about how one goes about identifying a fossil microbe in a 3.865 billion year old piece of chert…and how one debunks said identification. Great stuff so far; probes the temporal fringes of biology and sheds real light on research about which I’d long been curious.
Ich wuensche mir, dass ich Umlauten haette, dann waere ich echt supertoll!!!
I wish that I had umlauts, then I’d really be supercool!!!
Yes. And THIS is how cool you would be:
http://en.wikipedia.org/wiki/Heavy_metal_umlaut
Sorry, I should have said 3.465 billion year old chert. I couldn’t be bothered to run downstairs and check the book earlier with the result that my error encompassed a timespan roughly comparable to that stretching between the heydey of the trilobites and the heydey of this blog. For all I know I’ve now spelled “heydey” incorrectly.
my error encompassed a timespan roughly comparable to that stretching between the heydey of the trilobites and the heydey of this blog
Pah, what’s 400Myr between friends? Trilobites, humans — can’t tell these lumbering metazoans apart anyway. And don’t let me get started on how those uppity mitochondria got all cozy with the eukaryotes. Disgusting….
Ich wuensche mir, dass ich Umlauten haette, dann waere ich echt supertoll!!!
Das kommt mir komisch vor.
I especially loved the crafty avoidance of umlauts. ;)
I’ve been reading pharygula for a quite some time now. It’s sad that my first comment is on PZ cracking me up. The “three umlaut name” schtick is making the rounds in my email now.
Thanks for making evolutionary biology fun PZ!
Here’s the abstract of a difficult but fascinating paper discussing one metabolism-first model. They make a good case, with the expected uncertainties (honestly discussed).
I’d post the link, but I lost it; I do have a pdf file of the paper, so I can email it to anyone who wants a copy. (It’s a difficult read! It’s certainly not a “Door A” solution)
Journal of the Geological Society, London, Vol. 154, 1997, pp. 377-402…
The emergence of life from iron monosulphide bubbles at a submarine hydrothermal redox and pH front
M. J. RUSSELL & A. J. HALL Department of Geology and Applied Geology, University of Glasgow, Glasgow G12 8QQ, UK
Abstract: Here we argue that life emerged on Earth from a redox and pH front at c. 4.2 Ga. This front occurred where hot (c. 150C), extremely reduced, alkaline, bisulphide-bearing, submarine seepage waters interfaced with the acid, warm (c. 90C), iron-bearing Hadean ocean. The low pH of the ocean was imparted by the ten bars of CO2 considered to dominate the Hadean atmosphere/hydrosphere. Disequilibrium between the two solutions was maintained by the spontaneous precipitation of a colloidal FeS membrane. Iron monosulphide bubbles comprising this membrane were inflated by the hydrothermal solution upon sulphide mounds at the seepage sites. Our hypothesis is that the FeS membrane, laced with nickel, acted as a semipermeable catalytic boundary between the two fluids, encouraging synthesis of organic anions by hydrogenation and carboxylation of hydrothermal organic primers. The ocean provided carbonate, phosphate, iron, nickel and protons; the hydrothermal solution was the source of ammonia, acetate, HS”, H2 and tungsten, as well as minor concentrations of organic sulphides and perhaps cyanide and acetaldehyde. The mean redox potential (ÃEh) across the membrane, with the energy to drive synthesis, would have approximated to 300 millivolts. The generation of organic anions would have led to an increase in osmotic pressure within the FeS bubbles. Thus osmotic pressure could take over from hydraulic pressure as the driving force for distension, budding and reproduction of the bubbles. Condensation of the organic molecules to polymers, particularly organic sulphides, was driven by pyrophosphate hydrolysis. Regeneration of pyrophosphate from the monophosphate in the membrane was facilitated by protons contributed from the Hadean ocean. This was the first use by a metabolizing system of protonmotive force (driven by natural ÃpH) which also would have amounted to c. 300 millivolts. Protonmotive force is the universal energy transduction mechanism of life. Taken together with the redox potential across the membrane, the total electrochemical and chemical energy available for protometabolism amounted to a continuous supply at more than half a volt. The role of the iron sulphide membrane in keeping the two solutions separated was appropriated by the newly synthesized organic sulphide polymers. This organic take-over of the membrane material led to the miniaturization of the metabolizing system. Information systems to govern replication could have developed penecontemporaneously in this same milieu. But iron, sulphur and phosphate, inorganic components of earliest life, continued to be involved in metabolism.
Keywords: greigite, hydrothermal conditions, iron sulphides, mackinawite, life origin, Eh.
One aspect that struck me is the importance of tungsten ions in prebiotic metabolism, and the continuing use of tungsten in some very basic modern biochemistry. (Tungsten?! )
(quote: “… tungsten is a required element in the metabolism of all hyperthermophilic bacteria … at the base of the evolutionary tree”)
“a three-umlaut scientist
I feel umlaut envy. I have to start using what I got.
At least you’ve got one already, Torbjörn. If you added a few more, you wouldn’t be a total poser.
Cool. Günter’s stuff is still relevant, apparently (I met him ten years ago when he came to visit Carl Woese in Illinois). I think it’s cool that a patent lawyer like Wächtershäuser (he does have a doctorate in chemistry besides his law degree, true), can do research on the side.
What religious title? “genesis” is a perfectly respectable word of Greek derivation meaning “the origin or coming into being of something”. The fact that that same word was also used to label a particular set of assertions (unsupported by evidence) about the supernatural origin or coming into being of lots of things is beside the point.
Life began with metabolism, and genetic molecules were incorporated later.
I don’t think that can fly, on definitional grounds. I think if you don’t have some sort of self-replication, it wouldn’t be called life.
“three-umlaut scientist” LOL!
I’d buy the Reese’s moment: “You got enzymes in my lipospheres!”
I’ve also heard suggestions that surfaces, notably clay particles, had a major catalytic role.
“I think it’s cool that a patent lawyer like Wächtershäuser (he does have a doctorate in chemistry besides his law degree, true), can do research on the side.” So do I–echoes of another patent attorney, Einstein. I first learned about Wächtershäuser’s work in the PBS companion book to Origins. Fascinating stuff. Origins says that his education in chemistry and biology is largely self-taught.
(I have two dotted i’s in my name, can that count as an umlaut?)
“At least you’ve got one already, Torbjörn. If you added a few more, you wouldn’t be a total poser.”
That’s too bad, I thought I was really doing it this time. Perhaps I should start a company that sells Tötal Pöser (TM) licenses?
Since I know the owner, I bet I can get a license for free, too!
djlactin-
Damn, what a cool paper (from my biologically retarded chemist’s point of view).
I still like A.G. Cairn-Smith’s clay ‘genetic takeover’ hypothesis. “7 Clues to the origin of life” comes at it from a pretty pedestrian perspective. Somewhere, I have a chapter galley from a more recent book A.G. sent me when I was a post-doc. I think it was abiogenesis related (but might just be an odd chapter in a clay chemistry book). If I can find it and it looks promising I’ll post the title.
Dave Eaton…. glad you liked it. (are you referring to the whole paper or the abstract?) have the obverse of your problem: to me was fascinating from a chemically-retarded biologist’s point of view. i got more than a little bogged down in the geochemical jargon, but i was able to get the gist. the hypothesis seems entirely plausible to me. whether it actually did happen or not, well… 4.2 biliion years was a long time ago.
As for other proposed mechanisms… who’s to say that life only arose once? all we can say is that all current life forms descended from one origin: the ‘best’ (or ‘luckiest’?) one OR (as seems to be the consensus) from a ‘best/luckiest’ combination of 2 or more protolife forms… metabolism + xNA for example.
As an aside, I think that “origin of life research” has a serious problem in that there does not seem to be an agreed-upon definition of ‘life’.
I think that “origin of life research” has a serious problem in that there does not seem to be an agreed-upon definition of ‘life’.
I was under the impression that this was only really a problem for the journalists reporting it – shurely there’s no need for a Frankenstein moment? OoL research is more about finding all the dots than about finding The Dot, no?
Of course, there’s a religious version of the peanut butter cup scenario as well.
http://www.goats.com/archive/980313.html
I come to this discussion a year late.
A few weeks ago, I picked up Christian de Duve’s Vital Dust and 22 pages in, he’s detailed some of the things we don’t know, circa 1995, when the book was written. Knowing biology research is in continual ferment, I wondered how much more has been learned in the 12 years since.
After skulking around a bit I found Hazen’s book. It seems to be the most balanced and comprehensive overview of origins study available to date, and it also notes that we have much more to learn. But as PZ points out, Hazen also reports on the directions further research is taking.
I’m encouraged – thanks, Kristine – by the mention that Wächtershäuser is largely self-taught. That’s the only way I’m ever going to get a deeper understanding of the subject. And thanks, PZ, for giving us your informed perspective. I’m delighted to find my impression – that this is a solid book and a fine introduction to the field – is valid. I’m nearly halfway through now and enjoying every minute of it.
Dr Dave:
“That one is on my reading list, but I’ll have to admit that the last reccommendation I acted on (the evo-devo book whose name escapes me now… you know the one) I found interesting but somewhat impenetrable to a non-biologist. I faded out well before the midway point.”
Me too. Robert Hazen also does an origens of life course on DVD (teach-12.com). It is really excellent and needs no prior knowledge. I highly recommend it and his book is probably equally understandable
It is totally ‘gay’ to title the book Genesis even though the word isn’t ‘owned’ by the Church. It just leads to confusion and possible cross dressing.
Enjoy.