Interview with Roger Buick
May 2, 2005
CI: How did you start your higher education?
RB: I studied biology at the
CI: As a kid were you always inclined towards science?
RB: Oh yes! I always wanted to be a scientist, a
natural scientist of some sort. I collected rocks and minerals, shells,
butterflies, and had a fish tank. I lived in
CI: What were you doing in
RB: My father was a librarian and set up the
library at the
CI: How long have you been at the
RB: About three and one-half years.
CI: It’s a great group up there, for what you do.
RB: Oh, yeah! I had always felt like somewhat of a scientific orphan until this word astrobiology was invented, because I called myself a paleo-bio-geo-chemo-techtono-strato-sedimentologist who worked on the Archean. When astrobiology came around they said, “Oh no, you’re an astrobiologist,” which made it a lot easier to explain to people what I actually did.
CI: Most scientists are very specialized, sometimes to the detriment of science. You’re unusual in that you work in an intrinsically interdisciplinary way. What have been the pluses and minuses of that type of work in your career?
RB: It takes an awful lot longer to master an interdisciplinary area of science. But it brings insights that are much more likely to be novel, because you’re bringing a unique combination of information and outlook to the area. Working somewhere in between biological and earth science is mentally stimulating. Then you have astrobiology, which involves astronomy and oceanography and aeronautical engineering and all this other stuff. I’m by no means the master of any of those other areas, but each little incremental bit of knowledge from another scientific discipline helps you see and think about things in a different way. I’ve been working the last couple of years with an atmospheric scientist and am now working with a postdoc on building computer box models of early atmospheres. It’s something that would have been inconceivable to me five years ago.
CI: Let’s start with your background in geology and paleontology. If we’re asking the standard Guinness Book of Records question, what is the oldest rock?
RB: Well the oldest fragment of rock is an individual zircon crystal that dates back to 4.4 billion years.
CI: Is that primeval?
RB: That’s within 150 million years of Earth
forming, yes. That crystal actually comes from northwestern
CI: I think most people don’t realize just how hard it is to find old rocks…several billion year old rocks. Can you talk about how we’ve homed in on a rather small set of places where these valuable specimens can be found?
RB: It’s not just that it’s difficult to find old rocks. Anything old is difficult to find—how many people do you know that are a hundred years old? Not many. It’s also difficult to find old objects that are well preserved. Old rocks tend to have been battered by the vicissitudes of life—heating and pressure, cooking and squashing—metamorphism in other words. And most really old rocks that we find have been so metamorphosed that they’re unlikely to contain any decipherable relics of early life.
are two or three places on Earth, mostly in the interior of continents, where rocks
have been protected from plate tectonic processes for a long time and we find
old rocks that are moderately well preserved. Now by “moderately well preserved,”
I mean by old rock standards. Usually geologists just throw up their hands in
horror and say “These rocks are too wrecked to be able to do anything with.” But
you can do things with them if you work from first principles, are pretty
cautious in your interpretations, and spend a lot of time getting all the background
information absolutely right before you start trying to find life traces in
them. That’s basically what I’ve spent the last thirty years doing: getting to
know one patch of rocks in the northwest of
CI: Has there been resurfacing even in these relatively well preserved regions? Or are the strata that you’re interested in fairly accessible?
RB: They’re reasonably accessible. In northwestern
me about fieldwork in
RB: There are a couple of towns there. Also some big iron ore deposits in the region which means there are a couple of big mines as well. But where I work it would be fifty miles to the nearest person. It’s very hot, dry, desert with hurricanes in the summer, and plenty of humidity. In the winter it’s not bad; the temperature is in the high eighties and it’s quite pleasant.
CI: What type of technology do you take with you in the field to gather your samples?
RB: Just a sledgehammer—pretty low-tech.
CI: Is there any dangerous wildlife you need to fend off with a sledgehammer?
RB: Snakes, camels, scorpions …
RB: Yes. But no lions and tigers or anything like that; it’s a pretty benign environment, apart from the snakes.
CI: How do you home in on the best rocks? I mean, to someone who is uninformed, the strata and rocks and outcroppings would seem to be an undifferentiated wilderness.
RB: The best strategy I’ve found is to map it. Geological mapping is not something that’s widely practiced anymore, but I try to teach all of my students how to do it. When you create geological maps, you’re forced to look at the rocks very closely and work out how they formed and how they relate to other rocks. You’re also forced to cover the country, walk up every hill, and smash open every rock. That’s how you find out which strata are likely to be the best for finding signs of ancient life. So, I’ve found mapping to be a very productive strategy.
CI: Presumably the oil companies also use that kind of technique.
RB: No, they don’t any more! Now that the world’s gone high-tech, they think they can do it from space.
RB: And it doesn’t work. What works is boots on the ground, swinging a hammer, smashing every rock to have a look at it, and marching fifteen miles a day up and down mountains. It’s slow, and it’s intellectually taxing. Basically you’re trying to put together a four dimensional story about what the rocks are doing in one particular area. Not many people do it because it’s hard work; it’s a relic technique from the grand old days of frontier exploration.
CI: When you’re in the field, how do you record everything? Do you keep a notebook? Or do you use a laptop?
RB: There are two principal techniques that I
use. I take a field notebook, and record every observation I make at every
particular point. I also take aerial photographs with me. I map onto
photographs, draw lines at every rock boundary and mark points where I take a
sample. These days I use a GPS as well, now that they’ve become more reliable
CI: Do your photos have about a meter’s resolution?
RB: You can see each individual tree on it, so it’s a couple of meters resolution.
CI: What’s your ideal field team?
RB: I like to do it alone, but it’s unwise in that sort of environment because if something happens, you fall and break a leg or something, you’re dead. So usually I take someone with me, like a grad student. I spent two years up there alone mapping for a mining company and that was great fun. We had two-way radios so if one of us didn’t report in at the end of the day the rest of the mapping team would scramble and try to find them.
CI: Have you ever been in a sticky spot while you’re on your own?
RB: Yes, several times. I’ve had vehicles blow up on me; I’ve had to walk about thirty-five miles out with no water—that wasn’t fun. That’s about the worse that’s happened.
CI: I don’t want to romanticize or mysticize your science, but there must be at some level an art to it, at least in terms of noticing things, because there’s so much that you could notice. Is that awareness so natural to you now that you can instantly gravitate to the most interesting outcroppings?
RB: In northwestern
CI: That transition from bewilderment to recognition and understanding is a very experiential thing. Obviously you’ve studied all possible geological formations and have stared at photographs of all parts of the world, so intellectually and conceptually you do know most kinds of geologies that you might run across?
RB: Intellectually I do, but it takes a long
time to train your eyes to see what’s important. In different parts of the world,
rocks are exposed differently. They’re different colors, they show different
textures, and you can’t get two more dissimilar places than
CI: That must also be modulated by the lighting conditions, because the way surfaces appear in the early morning or mid-day are very different. Is there a time when the lighting conditions are best for doing the work?
RB: Not in
CI: It sounds like it’s an intensely experimental science—something that you couldn’t convey very well in a textbook.
RB: Yeah, I’ve never seen a really good textbook for teaching field geology. As you say, there’s an art to it; some people are naturally good at it and other people just never quite get it. You’ve got to be able to think in four dimensions at the same time that you’re using two or three different senses to understand the rocks. You’re working on scales ranging from sub-millimeter to many kilometers, so at any one time you’re integrating several different intellectual tasks. But you’re doing it without realizing it because you don’t go through a conscious process when you’re working a rock.
CI: For training, it seems like the best apprenticeship for students is in the field—it’s almost the only apprenticeship that matters.
RB: For the work I do, yes, I agree. It’s like learning to cook—you have to stand in the kitchen and watch and ask questions and think while you’re watching.
CI: Let me move towards the early life issues. I’d like to ask an epistemological question. In your field, the most valuable commodities—old unaltered rocks—are rare. Interpreting the evidence for early life must be difficult. What issues arise in terms of the nature of the evidence?
RB: Well, the first really big concern is trying to distinguish life from non-life. All life forms are carbon based. But when we find little one micron spheres of carbon, how do we know whether those spheres are remnants of a microbe bottle or if they’re a non-biological aggregation of dead carbon?
The second difficulty is the question of how we would know independent relics of the earliest life if we found them. We assume that the process of evolution has been pretty continuous, and that very early life is going to be like primitive life on Earth now. But what if there were early failed evolutionary experiments? How would we recognize them?
CI: I remember the work of Raup and Sepkowski and their idea of multiple origin events in the epoch of heavy bombardment. What’s the evidence for multiple starts to life?
RB: Currently we have no evidence for multiple origins of life. We’re somewhat limited by the scarcity of well-preserved old rocks, particularly in the first half-billion years of Earth’s history where we have no sedimentary record at all. Without a sedimentary rock record, it’s exceedingly difficult to find relics of independent origins of life other than the current strain.
current strain of life got established on Earth it presumably out-competed any
other independent origins fairly quickly. You just have to look at the history
of animal life to see how it could have happened. In the Cambrian, for
instance, 540 million years ago, in really good fossil deposits like the Burgess
Those are the two big biological issues, but then there’s one more imparted by the geology which is the concern of contamination. If you have a rock that’s 3.5 billion years old, there’s ample time in that long long history for it to be contaminated with some younger biological entity. Those are the three big epistemological issues.
CI: It seems some scientists support the idea that life formed almost as soon as you imagine it could, given the inhospitable conditions.
RB: Everyone thinks of the origin of life as being an extremely improbable event, but if the conditions were right for it to happen once, then they might have been right for it to happen multiple times. Maybe only one strain of life ended up being the successful competitor.
CI: The evidence supporting the timeframe in which early life formed seems controversial. Maybe you can summarize that for me.
RB: There’s no shadow of a doubt that the planet was voluptuously and voluminously inhabited by diverse life forms as far back as about 3.25 billion years ago. Multiple converging lines of evidence support a wide range of metabolic styles operating at that time. At 3.5 billion years, there are still many different lines of evidence that the planet was truly inhabited.
billion years it starts to get difficult because we’re restricted to two sets
of rocks in
CI: Say a little bit about the nature of fossils. Many people know that the fossil record runs out at some point, but they probably don’t understand what type of evidence you can find that far back.
RB: There are four different sorts of fossils you can look for in the early Earth. The first are the dead bodies themselves. But that’s not easy, because as far as we can tell, before about a billion years ago all life was microscopic. You can’t just go to a rock and find a fossil in the field like you can with a fossil clam and say “Ah-ha, I’ve found a fossil.” You would have to collect rocks that look like they have the highest likelihood of containing body fossils and then bring them back to the lab, slice them up very thinly, and investigate them under a microscope. That’s a difficult process, so not many body fossils of early microbes have been found. The oldest ones that everyone would agree on are only about 2.5 billion years old.
CI: Are they multicellular? How big are they?
RB: They’re single celled! Think of a sphere of carbon, about a micron across, or a carbon tube five microns in diameter; that’s the size of them. So they’re exceedingly small, at the resolution limits of light microscopes. But if you can find them, I can tell you quite a lot. I can tell you what the organisms looked like, how they reproduced, if they happened to get fossilized in the act of reproduction. I can tell you in some cases if they’re capable of movement or not. Body fossils are good to find, but I don’t think we have any older than about 2.5 billion years.
The next type of fossil you can go looking for is a trace fossil. Which is not the actual remains of the organism itself, but something left behind as a result of the organism’s activities.
CI: Does this include stromatolites?
RB: Yes, stromatolites are trace fossils. They’re
visible to the naked eye, but they’re not the remains of the actual organism. They’re
You can get an idea of the size of the organisms from the thickness of layers in the stromatolites. You can tell what kind of habitat the organisms liked to live in. Sometimes you can infer the way the organisms made their living. Photosynthetic organisms, for instance, will often consume carbon dioxide and cause calcium carbonate to precipitate. So if you’ve got a stromatolite made of precipitated calcium carbonate you can deduce that those organisms were eating carbon dioxide.
CI: That’s interesting. To get a sense of the timescale, how old is the oldest stromatolite?
RB: Well, the oldest micro-fossils are 2.75 or
2.5 billion years old. The oldest stromatolites that I think everyone would
accept are about 3 billion years old. But in my opinion, there are very good
stromatolites that are 3.5 billion years old. They come from
CI: And the other two sorts of fossils?
RB: From trace fossils, you can go down to the even more remote level of molecular fossils. In that case, you don’t get the body of the organisms but you get a few stray molecules from the body preserved in rock. Oil, for instance, is a classic example of a molecular fossil of plankton. It used to be thought that hydrocarbon molecules wouldn’t survive heat and pressure and that it wouldn’t be useful to go looking for molecular fossils in really old rocks. But a few years ago we showed that you could get hydrocarbon molecules derived from once-living organisms in rocks as old as 3.25 billion years. These can tell you all sorts of things because different organisms leave different molecular traces. For instance, if we were to bury you in a rock—we’ll kill you first, we’ll bury you in the sediment…
CI: That’s nice…
RB: …we’ll heat you and squash you a moderate degree so that all traces of your body are destroyed. But there would be an ooze of organic molecules left behind. From that ooze we would be able to work out that you had complex cells with a nucleus, we’d be able to work out what sort of metabolism you had, and we’d even be able to figure out if you had a high cholesterol level, because cholesterol survives extremely well in geological environments. Cholesterol is also a marker for our group of life, the eukaryotes, the organisms that have sex and complex cells.
CI: What about bacteria?
RB: Bacteria have completely different molecular fossils. They don’t produce a diverse range of molecules like cholesterol. So if you find hydrocarbon molecules in an old rock that has cholesterol, you know that our group of life had already evolved at that particular time. We’ve managed to show that our group of life, the eukaryotes, goes back at least 2.75 billion years.
CI: When you move from a trace fossil back to the molecular level, you’re losing some degree of information about the organism. What can you say when you’re limited to looking at molecular tracers?
RB: Once you get to molecular tracers, you can’t say too much about habitat, size, movement, or shape. But you can say more about metabolism and how the organisms made their living. For instance, cyanobacteria, which are the main photosynthesizers on the planet now—the things that take up carbon dioxide and water and turn it into sugars and oxygen—have a distinctive biomarker molecule. If you find that particular molecule in old rocks, and especially if you find large amounts of it, you can be almost certain that there are oxygen photosynthesizers around, because even the most primitive cyanobacteria have the capability of oxygenic photosynthesis. We can find that molecule in rocks half-a-billion years before sedimentary rocks tell us that oxygen had started building up in the atmosphere. The ability to produce oxygen evolved well before the relics of oxygen started appearing in the geological record.
CI: Is contamination a problem in molecular fossils?
RB: Yes, because oil can flow from one rock to another. You can have recent contamination—we live in an environment where there is contamination from petroleum just about everywhere. When a diesel truck goes past your window that black smoke is blowing biological molecules over your precious sample. But the good thing is that the molecular fossils have distinctive patterns that can tell you that they’re not contaminants. The oldest confirmed molecular fossils are 2.75 billion years old.
CI: So even though there are no cell walls or anything, the contamination issue can be bypassed and the biochemical tracers clearly point to living organisms? Could they be misinterpreted?
RB: Cholesterol, for instance, is strictly a biological molecule. If you find lots of cholesterol or its geological derivative in old rocks, you know it has to be biological. There is no natural process that synthesizes cholesterol from methane and carbon dioxide—it just doesn’t happen. Cholesterol is a beautiful molecule. Much as you might hate it, it is a wonderful thing.
CI: What is your favorite fossil?
RB: My favorite is a 3.5 billion year old stromatolite. I found it during the first year of my Ph.D. work. But what’s sitting in front of me right now is a representative of old Martian rocks and it contains atomic fossils. That’s going down to an even finer scale than molecular fossils. Atomic fossils are biological elements that show a distinct isotopic ratio that’s different from the non-biological world. For example, the carbon that makes up your body has a different isotopic ratio than the calcium carbonate in marble.
in front of me is a chunk of 3.5 billion year old barite from
CI: Are atomic level tracers the primary evidence in this tantalizing zone of 3.5 to 4 billion years ago?
RB: Pretty much, apart from the stromatolites. I think there are good stromatolites at 3.5 billion years, but if you take the conservative view the oldest are 3 billion years old. By the time we get to 3.5 or 3.75 billion years ago, we’re down to a strictly atomic level evidence of life—isotopes of carbon and sulfur indicating that biological, metabolic processes like photosynthesis or sulfide reduction were taking place.
CI: How can you be sure that you know all the metabolic mechanisms that are operating? And given that the tracers become more inconsistent at the atomic level, how do you confirm biological origins when you have to worry about things like natural isotopic variations?
RB: Yes, that’s very true; there are non-biological processes that can fractionate the isotopes of biological elements. But biological fractionations are often extreme. Non-biological processes that fractionate isotopes are usually relatively mild and are usually inconsistent in their changes from environment to environment. So we look for consistency and magnitude before we start believing that things are biological.
CI: How does the good hard evidence that you gather play into the theoretical debate over the mechanisms of the earliest life? There are a lot of ideas about whether or not metabolism came first and when the first replicating molecule appeared. What kinds of ideas do you hope to contribute to that debate?
RB: I’d like to be able to say what the earliest preserved organisms were like on Earth. And from that other scientists could extrapolate and say, “OK, maybe 3.5 billion years ago life had this kind of metabolism and was capable of living in these sorts of habitats, and had these sorts of skills.” If it is indeed true that the late heavy bombardment sterilized Earth, we may have had a relatively short window for the origin of our current strain of life. So if we can get fossil evidence of life a few hundred million years after its origin, it will inform us about the origin of life question in general. But my guess is it’s not going to work out like that because more and more we seem to be finding that life was almost modern in its sophistication even 3 or 3.5 billion years ago.
CI: The issue of complexity is often tossed about in an imprecise way. I’ve read that life developed an extraordinary metabolic diversity very quickly. When you consider the extremophiles, the range of habitats and range of metabolisms is amazing. How does what we’re learning about early life on Earth address that issue of complexity with regards to the developmental timescale of more sophisticated organisms? Why did it take so long to go to multicellularity?
RB: I don’t know—bacteria do very well with their genetic exchange capabilities and maybe we over-rate complexity just because we are complex.
CI: Also, there are organisms like stromatolites that have been successful for huge time spans without advancing beyond a certain stage. How do we decide, in our study of Earth, what is necessary and what is contingent when you’re talking about the evolution of life?
RB: That’s hard to answer. It would really help if we had another strain of life evolving in parallel on Earth, or if we had evidence of an independent origin of life, or if we had could compare it to life on another planet. Having just one paleontological narrative to read means that it’s difficult to determine what’s necessary and what’s contingent.
CI: This whole discussion reminds me of the
Mars rock. These issues and uncertainties seem to be a nice microcosm of the
debate over the
RB: Well, there were four lines of evidence for signs of life in that Mars meteorite, and three of them have been pretty categorically debunked. The jury is still out on the last, but the window is narrowing. I think the likelihood that the meteorite contains evidence of life is pretty low.
The same issues that face early evidence of life on Earth apply to evidence of life on early Mars. First, whether it’s a uniquely biological phenomenon and second if it’s truly indigenous to the rock. Contamination is a big concern. What if life on Mars was different from the life that we are used to? On a different planet, there’s a much higher likelihood that life might be unfamiliar or fantastic to us. So even though we might be able to overcome problems of contamination, we might not recognize signs of life in a Mars rock because we’re wearing our terrestrial-tinted glasses while looking at the fossil evidence. There’s always that worry that evidence might be staring us in the face and we wouldn’t recognize it.
CI: There seems to be a dichotomy among scientists who talk about the likelihood of life elsewhere in the universe. Either they talk about life existing at a primitive microbial level, or at an intelligent, advanced level.
CI: We have one history to read on Earth, but we have cosmic ingredients of life that are widespread. Now we also have evidence that planets, even terrestrial planets, will be widespread. Within our own Solar System, the newly expanded envelope of extremophiles on Earth raises expectations of microbial life. Given the diversity of microbial life on Earth, what do you expect to find when we start inspecting other habitats?
RB: Earth is a pretty unusual planet. There will be rocky planets elsewhere, but their number is reduced when you look for one that’s rocky, about this size, has the volatile endowment of Earth, and has a similar orbital and thermal regime relative to its star.
I think microbial life has probably arisen often in the universe, and may possibly have arisen elsewhere in the Solar System. The fact that there is diverse and biochemically sophisticated microbial life very early in Earth’s history suggests that it’s not difficult to get to a self-supporting, metabolic ecosystem of microbes. But if it is indeed necessary for billions of years of evolution to take place before morphological complexity and intelligence arises, I think it’s very unlikely that anything much more than microbial life will have appeared anywhere in our galactic neighborhood.
CI: But if extremophiles have such large physical ranges, and accepting that Earth is somewhat unusual, won’t we just find an even larger metabolic diversity in more extreme environments?
RB: Independent origins of life could have produced biochemical systems that could withstand environmental conditions beyond the range of our strain of life. I’m sure there are other forms of carbon biochemistry. They may even include non-carbon biochemistry. I think microbial life is reasonably abundant.
CI: Which of the potential habitable sites within the Solar System is most interesting to you?
RB: Mars! Early Mars looks just like
CI: The “Ah-ha” moments in science are rarer than the movies and TV would have you imagine; science is more of an incremental process. But if you’re fantasizing, what would be the most exciting thing for you to find that would vault your work or the evidence you work with to a different level?
RB: If the origin of life experiment that I’m carrying out in the basement with a graduate student actually succeeded and produced an independent origin of life that we could let evolve.
CI: It’s a Miller-Urey experiment? What are you doing in your basement?
RB: We have a vat of early Archean environment that we’re letting sit there and stew to see if life could originate under plausible early environmental conditions. The original Miller-Urey experiment wasn’t a very plausible early Archean environment.
CI: Right. The fundamental problem, I guess, with all such experiments is how to mimic the huge times scales that were required.
RB: Sure, but were they really required? In the right environmental conditions, I could imagine that life might have originated pretty quickly, and not have needed hundreds of millions of years. If conditions are right, I think it can happen fast.
CI: The work you do almost sounds ideal, because you get to stay rooted in your field work and add to its intellectual pursuit through many interdisciplinary strands.
RB: Yes, exactly, that’s the great thing about astrobiology. It’s multi-disciplinary, not just interdisciplinary. To be an astrobiologist you need some awareness of half a dozen different disciplines.
CI: The snapshot of the astrobiology field is nicely done down at the NASA Astrobiology Institute meetings. Besides your Archean experiment, what are the things, perhaps outside your field that you find most exciting right now?
RB: I would say the discovery of extrasolar planets and the planetary science being done on Mars and Europa are the two things that really excite me. Also, some of the extremophile work—just finding more and more places where bugs can live is very exciting.