welcome to the science for the public lecture series science for the public is an organization committed to bringing science information issues to the general public this is our website for our program discuss this we have one of the leaders and probably the leader in firmly establishing the nature of that co evolution and all fisher professor of natural history and professor also of earth and planetary science s harvard university dr knoll is a member of the national academy of sciences the american academy of arts and sciences the american philosophical society and the american academy of microbiology he's received many awards and there is a list on tonight's event page on our website which includes a link to his harvard website one of those awards i do want to mention was the five beta kappa of book award in science for his outstanding two thousand and three book life on a young planet the first three billion years of life on earth which we'll also discuss tonight dr noll scientific contributions are so extensive it's hard to know where to begin or end so i'm going to try to take a deep breath and summarize first by saying dr in all is a great scientist who among other things pioneered methods for to find a biological traces of very ancient organisms that did not have or leave shells or bone in that period tonight dr noll shares his scientific adventures in tracing the relationship between the evolution of life and the evolution of this planet and his contributions to a den of find these traces of ancient organisms in sediments and rocks this expertise has been applied also to his work on the nasa's mars exploration rover mission which has led the search for the history of that planet it is a very great honor to welcome d phil welcome thank you for being here and i'd like to ask right out front since this is one of the things you're so well known for about the co evolution of life and the planet we're usually we usually hear evolution organisms and the rest of it is dropped out but you've spent decades on putting this together what does it mean well i should say that the idea that life in the physical planet are sort of intricately bound both in space and time certainly didn't originate with me fight i've recently been reading a biography of alexander from humboldt who two hundred years ago articulated a clear vision that we couldn't understand individually the rocks the trees the in sacks the birds that we had to actually understand them as a system with interacting parts now in all honesty it was another hundred fifty years before scientists started taking that vision seriously but now there's really a discipline called earth system science and biological pro interact with physical processes on the earth and that determines the nature of the world we live in and how does that work with the kid you give like an example because we think we think that people like  geology you go out and look at the rocks and bring back samples and so on but we don't have a very good idea of what how that rock has changed how the sediments have changed as a result of life or vice versa right well one of the things that you have to understand about rocks is they have patterns in them there are physical patterns there are chemical patterns and if what we'd love to do is to look at it ancient rock and interpret those patterns in terms of the processes including biological processes that contributed to its formation and we would like to sort of extract a record of what the state of the environment was what was it like to be around at that time and in order to do that we actually have to start with the present day world and look at places where sediments are accumulating  in modern rocks we can actually see how microorganisms let's say contribute to the patterns that we see in the sediments then armed with that we can go back to rocks that are a billion years old organisms that you dealt with largely were micro organisms these interacted with the geology of the earth is that right to the chemistry of the atmosphere and so on yes and they still do  know when we walk down the street we could be forgiven for noticing plants and animals and not much else but even today the process sees that cycle carbon through the biosphere that cause cycles sulphur  all the elements that are important to us as organisms those cycles are completed largely by microorganisms we're really guests in their world not the reverse which is an interesting irony we keep trying to get rid of bacteria all the time it is a nice to them it's a terrible mistake it's a great thing that everyone feels queasy when they fret hear this but you and i each have something on the order of a thousand different types of bacteria so i could say you know our bodies and we could not live without them very few of those bacteria are harmful to us many of them don't really affect us one way or another but some of them are responsible for training your view and system for breaking down compounds so you can digest them even for the proper development of your digestive tract yeah so again we very much live in a world that shaped by bacteria and the important thing in terms of earth's history is that life had existed for three billion years before the first adam oates came on the scene so everything all the circuitry of process that sustain habitable environments on this planet that's really determined by microorganisms right did microorganisms have anything to do with particular types of rocks or sentiments that formed oh absolutely you know we're used to thinking of younger limestones that are made largely of shells and so that's very much a biological influence on how sediments are forming but if you go back farther in time you find that microorganisms were very much shaping the way carbonate minerals precipitated and and form structures on the sea floor you know if you go back to the first half of earth history of microbial metabolism on a world without oxygen so in ways both small and large microbes have left a signature throughout earth's history right so all that stuff we're mining the fact  yeah right so this there's the term bio do you know chemical which is kind of intimidating but you work so much on that but what is that that relative to this evolution ok well if we break it down first of all there is chemistry yeah and i'm always fond of saying that life is chemistry with a history that is all organisms there are chemical pathways that we all have and use and we use in gaining energy and carbon in making the constituent parts of our bodies and because of evolution the ways we do that actually changes through time so there's the chemistry the bio then comes from the fact that organisms participate in chemical cycling and the geo comes in because earth processes also participate so if you could actually label a carbon a you know it might be in carbon dioxide in the atmosphere one day photosynthesis would put it in a plant the next day that plant would be eaten by an animal the next day in time some of that carbon would just start accumulating on the sea floor and then geology takes over it will sit there for perhaps one hundred million years or more and then geological processes will push it into mountains it will erode it will go back into the cycles other cycles with other elements as well yes there's a biological there's a sulfur cycle which has is populated almost exclusively by microorganisms nitrogen cycles iron cycles and in fact when you look through earth history these cycles are linked so for the first half of earth's history before there was much oxygen in the atmosphere and surface oceans the iron cycle and the carbon cycle were linked very closely and we see that those relationships change through time in ways we try to understand so that was evolving to everything really did evolve but in a sense the planet is alive i mean that's what people have suggested in the important thing is that of all the processes that determine the world we live it many of them are biological you know even when i was a student it was common to think that the earth was this passive platform eola g sat on it without interacting with it very much now we know that's the farthest thing from the truth but there's this very very close intricate dance between life right so changes in for what you look for well in a sense that's what you do you go to the rocks and you take your pick and in my case we have to bring them back to the laboratory and tend to process them because if they're fossils they're tiny and many of the signatures of life are actually chemical yeah signatures but what we do is what someone studying dinosaurs would do it turns out that through the work of thousands of geologists for more than a century we have a pretty good sense of the distribution of rocks of different ages around the world so if i'm interested in let's say the dawn of animal life i would go to the library and say where would i find exceptionally well preserved outcrops of rocks that are six hundred million yamaha and then i identify those and then if the world works the way it should i can go in and look at them and collect rocks so we we don't go blindly into the field we go where previous geological work has told us we have a good chance as know what kind of rock you're looking for is a so on have said so in your case where you're looking for microbi signatures then you can take the samples and you may not be able to really analyze them on site is that yet but you take them back and look at you learn two things on site one is because eventually rocks are laid one bed on top of another through time you get a sense of time yeah by studying their ox in sequence and also because in particular the physical characteristics of sedimentary rocks are very good guy to the environment in which they were deposited we get really this multi dimensional sense of time and space and that's the framework we establish and that we then collect samples within that framework and then bring them back so the a lot goes on in the field a lot of reading art history ok if i recall i think you mentioned maybe in the book that and again it's because of the physical and chemical tatter sticks of the rock we can actually find limestones that are very similar in their character to these eight hundred million year old rocks from spitzbergen and if we look at their modern analogues they're in places like the bahamas so yes what is that high latitude now with i always it on exactly but you can just identify like its history in a lot of ways just by looking at the rocks with particularly good for preserving bacterial fossils is something called sure yeah lint it's basically courts are silicon dioxide and that actually forms almost like up a plastic in the rocks and envelops these textures so that i can collect these shirts in the field bring them back to the lab cut paper thin slices of them and then look at them under the microscope and you see microorganisms that were in two and a billion years ago that's amazing about the other interesting thing is that you kind of know they're in there as well you're either one of the wonderful things of about the book that i thought was very charming when when i read it was the references to jacob marley facts of evolution and i wonder if you could give us a little background how you decided to call them the jacob marley facts of the pollution and we'll talk  you about what those are that well a just because in reading a christmas carol by dickens there's this wonderful passage in the beginning that he says jacob marley is dead as a doornail and if you don't understand that you will never understand the wonders of my story and it just seemed to me that that was maybe a nice way to already under store or underscore some of the things that you really had to know in order to understand what i think that are in about the interest with respect to interactions with the environment is what we might call energy metabolism so plants which are photosynthetic take c o two and water and using energy from light convert that into sugar and oxygen gas we on the other hand are responding and we  ingest organic materials react them with oxygen during respiration and it's how we get our our energy and then we get rid of as byproduct c o two and water so the two processes together actually make a cycle so metabolism is very important in that it is metabolism is essentially the set of processes by which organisms interact chemically with with the physical earth now isotopes are a little bit more complicated but they're very very useful so let's just we know that there are elements hundred eighteen or whatever many there are now so oxygen is an element carbon is is an element but it turns out that most elements come in different sizes and what i mean by that let's take carbon that about ninety nine percent of all the carbon atoms on earth have six protons and six neutrons so they have weight of twelve about one percent of the carbon atoms have an extra neutron so it's carbon thirteen so a little bit heavier and then about apart for trillion is carbon fourteen which is radioactive and decays on a scale of a little over five thousand years half life now carbon thirteen and carbon twelve are both carbon in the sense that they will form the same kind of chemical bonds and have the same kind of interactions but because they have different weights the probability of carbon twelve versus carbon thirteen participating in these reactions is a little bit in which they participate are a little bit different and that ends up giving us signatures we can see through time so for example in photosynthesis plants will incorporate carbon dioxide with carbon twelve innit in preference to carbon dioxide with carbon thirteen and the difference between the environment and the carbon in plants because of this photosynthetic reaction is about twenty five parts per thousand pretty small but you can actually measure that with a mess beck trotter and so what's great about that is i can go back to iraq with three billion years old and have confidence that there was a biological carbon cycle driven by photosynthesis because that isotopic signature is preserved in the rocks and so we can study the biological participation in the carbon cycle in the sulfur cycle in the nitrogen cycle because of the way that organisms fraction eight these isotopes that's really particularly interest since it's sort of invisible to look at and it's also very accurate it sounds like it's very accurate is how old is that method did you develop this over time  well i i wouldn't say that i developed the chemical methods the some of the earliest uses of isotopes were done in this famous laboratories of the university of chicago after world war two i think our contribution was to say let's not just pick a sample off the shelf and look at it it's it's chemistry but let's actually collect our samples in that framework of time and space and then use that as the framework for interpret ing the isotopic chemistry and that has actually been very useful because it shows that chemistry varies as a function of environment what is surprising there and  also it shows us that the carbon cycle has worked differently through yeah there are systematic very it's through time that tell us something about just the environmental history of the planet so it's quite a record quite  so we had metabolism as one thing and then isotopes which is probably less familiar but extremely important for people and then geological changes and  oxygen revolution yes so oxygen which you and i need to exist for more than about three minutes has a very interesting history over the entire course of our planet's development and in some ways oxygen has been a major control on evolutionary history when we look at rocks deposited before about two point four billion years ago that is sort of the first two billion years of earth's history the fascinating thing to me is that all of the sudden entry rocks from that early era their chemistry tells us that there was essential you know oxygen in the environment now not a problem for life in that there are many organisms still today that thrive in the absence of oxygen in fact as many organisms that would die when they compete and so the basic cycling of carbon sulphur nitrogen was a stablished among these so called anaerobic might no organism organisms that don't use oxygen don't live where oxygen is present then about half a dozen different set of mentary and chemical signatures change about two point four billion years ago and they change in a way that tells us for the first time in earth history oxygen gas is becoming a permanent presence in the atmosphere and surface ocean so that's one of the great sea changes and at least in part that could only happen because of the evolution of a group of bacteria called sign a bacteria and sign a bacteria are the only organisms that ever evolve the capacity to use water as the source of electrons for photosynthesis and we have today really to the activity first of side of bacteria and later of algae and plants now the other thing to say about what happened two point four billion years ago is that that oxygen event during that interval it looks like there was certainly oxygen around but probably one to a couple percent of today's level so it's still a very different world and then only in the last five or six hundred million years do we get chemical signatures that the kind of oxygen rich environment that you and i can live in is coming just to exist and of course what's fascinating about that is what about the same time scale that chemistry suggests the atmosphere in oceans or we start seeing large animals that require a lot of oxygen to that i have like to because that is that's sort of your pe they are like it's a period that is bounded at the beginning by one of the largest ice ages we've ever seen and it's a period when the chemistry of rock suggests that things are changing things are becoming more modern with within that change i think first of all the oxygen change it was was it spotty or just yes  fact it's interesting that if you look at the ocean the record of the oceans say one hundred million years ago there are short intervals of time when the deep ocean seems to lose lose all its oxygen these only last couple tens of thousands of years and it's called ocean and oxic events and a friend of mine tim lyons of the university of california riverside has actually by analogy to that suggested  oxic events that is generally oxygen is low but you have spikes to higher levels and it goes down and then for some reason and we still debate with that is very near the pre said that's really not necessarily the case at all this is much more maybe gradual and these other people these other bacteria were just fine without yeah i think bacteria are just fine  simple was it marsh in in southern massachusetts there's plenty of oxygen at the surface a millimeter below the surface there's no oxygen but there's billions of microorganism there are many environments on earth today where there was no oxygen and those organisms whose metabolisms evolved early in earth history still thrive there and in fact we actually require those organisms to complete the biological cycles of carbon sulphur a night or day so they're they're important right as they state important in that time that when there was a sort of gradual shift going on in in this time you i think have pointed out there's a lot of you might say up he fall in terms of the earth itself is that truth that the earth  whatever few things are going there's an ice age are six of them or however many who said slushie just ask you about that but there are these earth things that are affecting how life is changing apparently well that's right again it's the idea the earth and life are our interacting and the interval immediately before the initial radiation of animals largest ice ages we have have ever seen the carbon cycle is working somewhat differently than it does now and it's really that framework of changing physical environments that provides the stage on which animals first evolve and so one of the things that you know we still debate and we're still trying to understand is just how do all these components fit together yeah we know they're all there we know that the product of all of this at the end of the day was an oxygen rich world with large animals in it and exactly how the different components of the environment interesting period where you have the evidently a relationship that might be quite important that is geological and i would on one say at maybe atmosphere organisms themselves but i would say that the genetic changes have to work in concert with the environmental changes as you can't unless you have sufficient oxygen to support say large carnivores which appear for the first time in the cambrian period they can't evolve ok so large gains in some ways i always think of the this as having genetic possibility and environmental opportunity and the two actually hang linked together ok in a sense that's not too different from what we see maybe on a less grand scale throughout the next five hundred million years that is the environment changes that makes possible who innovations right at the same time sometimes new biological innovations will push the environment in a direction that will have consequences for biology so it isn't simply that this dance of earth and life played out in the deepest of earth's history it plays out today and of course we are living at a time of geologically rapid change in the environment and i think we have to be aware that earth the life wife is going to respond to those changes exactly exactly in that period then these first organisms i think were colonies i think you've pointed that out you have the sponges you have the jellyfish kinds of things these are symbiotic a relationships it seems like very often is there a reason for that well certainly you know in order to have any chance of interpret these oldest atom will fossils you have to look for the clues that we might get from organisms that are living today  most people don't even know about called plaque is owens little animals that are only a few millimeters long live in the oceans today and those are basically a little more than sheets of cells with a little bit of fluid in between them and they get their organic matter by you know absorbing molecules they get their oxygen by absorbing oxygen and we think that many of the first macroscopic or larger animals we see during  this period were actually somewhat similar they're much larger but they seem to have been upper and lower cell sheets maybe a little more tell you want to get you know human jellyfish in between them and so these little rare animals that live today may tell us something important about how the animals that are most conspicuous us in the early record first function and then finally the new darin's which we think of as coral jelly fish portuguese man of war and that again they have tissues but they don't have complicated organs and if you look at the complexity of a portuguese man of war it's because it actually is a c it might have a dozen different individuals in it one would be specialized for reproduction want to specialized for being afloat one is specialized for predation or or yes and that and you know before we had a world populated by organisms like us the discreet organ systems that was that the way to get complex yeah was to the list of very interesting you know characteristic that it went that way that seems very logical when symmetry that separates the two sides and organisms that have that kind of symmetry have organs digestive systems and so rather than specializing individuals within a colony for different functions you specialized organ systems within an individual and of course today we don't really know how many species of animal there are but a lot of people think there's ten million of them and  to just go back to that ice age before this again because you had i think quite a bit saying about it there was a big die off is that correct in that period was the four brian harland who was the person who first introduced me to pittsburgh and wrote a paper saying you know these things are all over the world there must have been a global ice age and then using tools of paleo magnetism which allowed people to say these glaciers were reaching sea level within ten degrees of the equator which is something very different from him we know it became clear that in fact there paul really worked out what was going on in an interesting way and there's no question that these were uniquely large ice ages there's still debate as to whether the dollar years ago suggested and more recent evidence has supported the idea that some of the diversity particularly of algae and protozoans that we see leading up to these ice ages disappears so certainly there was a calling of diversity at the time of these ice ages on the other hand it's pretty clear that many lines of organisms existed through the ice ages and persevered and would i think one of the things we have to bear in mind is it isn't as though there's ice here on a thursday and then all of a sudden we began i'm here saturday walking around the first record we have of large animals that you can see with your naked eye is really about fifty million years it took a while so it it took a while certainly these major ice ages are part and parcel of a series of  changes to the atmosphere and oceans and how the carbon cycle is working and that whole framework eventually ends up with a world with more oxygen and that then is a world where you can have trouble bites and i think that right but it took that what i'm not clear on is whether that would have happened without the ice age period in there where there's just so much going on in that period that we  certain genetic requirements for large animals it's not obvious to me that an ice ages is for being that to any extent but as i said you also need geology all of these things were part and parcel of something that's exactly right out there are part of in some ways some of the largest changes the earth has ever seen and a world without holes is the i don't know how much our viewers know about this project what is the application of this tremendous background and expertise well i became involved in this in the late ninety's when a guy named steve squyres from port au and wow putting our other proposal to nasa and steve weisman i thought that he didn't want to science team just made up of people who built and ran instruments but that he wanted it was very exciting moment when we the first pictures we saw from the rover when it landed showed that it had landed about five meters from an outcropping of set by rod ness and so once you know there are se griffith that is layered rocks then really what we did for the next decade is what i've done my whole life in the field you measure the sections you look at the valleys ical and chemical characteristics of the rock and through that and you know in conjunction with other information that other missions have given us on mars we've been able to build an increasingly good environmental history of one hundred just at amazing all remote and what have you learned about that planet that well i think chris you most i think one of the things that's interesting is if you look at mars today it is a desperately cold and hostile place is probably not a place that you would think of as a good environment for any life we know about today and so the question was and this goes back many years people suggested that maybe that's mars today history mars was very different and much more like earth and even as early as the one nine hundred seventy s with the viking missions it became clear that when you look at the martian surface there are channels on it and those channels are made by running water so we know that there is a water history on mars and one of the things that we learned through the m that the transition from a certainly wet her and possibly wet mars to the very forbidding mars that we see today actually happened fairly early in mars history that is if he's it's hard to know dates exactly on mars but about three billion years ago which is when we are seeing life becoming abundant on earth that is when you know ha there are certain minerals that formed early in martian history more than three billion years ago and those minerals require water to form but on earth those minerals don't last very long because if they stay in contact with water eventually they will transform into something else and the simple observation that these sort of juvenile minerals if you will the form billions of years ago are still sitting there just that over extremely long time period or periods they have seen very very little water and many lines of evidence actually agree on that that you know i wanted to go on with some other things i will have to say quickly i hope you write another book for the this is basically for the general public i think it is very readable very interesting and one of the richest sources by far for like evolution in general because it's so comprehensive and it's really helpful book so i hope that people will get it it's in the libraries and regret that i cannot go on where about out of time but i really appreciate your giving us this wealth of information thank you so much