Bob McDonald: Are we alone? On this tiny little orb on the outer spiral arm of a fairly run-of-the-mill galaxy in a very very large universe. Are we the only example of the miracle of complex life? Well we've been asking that question ever since we first understood that there was a universe. And as our understanding has expanded, and the immensity of the cosmos has become more apparent, many have claimed that we can’t possibly be alone. They say that the universe is just too big for the accidents that created intelligent life here, not to have happened millions of times elsewhere. But now two American scientists have challenged that conventional wisdom. In a new book called “Rare Earth”, paleontologist Peter Ward and astronomer Donald Brownlee, suggest that the particular and peculiar set of circumstances that lead to intelligent creatures like us may be extremely unlikely - possibly even unique. Of course no one knows for sure, but the book has created some lively debate. And joining me now are two people with very different views on the subject; Dr. Peter Ward is one of the authors of “Rare Earth” and a paleontologist from the University of Washington in Seattle.  And Dr. Seth Shostak is an astronomer from the Search for Extra Terrestrial Intelligence, or SETI Institute, in Mountain View California; a group that’s been looking for signals from other intelligent life in the universe.

Bob McDonald: Gentlemen. Welcome to the program.

Both Guests: Good to be here Bob

Bob McDonald: Now first of all Dr. Shostak, I’d like to start with you by asking you just for some background here, why is it that so many scientists think that life should be common in the universe?

Seth Shostak: Well, in some sense Bob this just goes back to Copernicus. I mean for the last four hundred and fifty years astronomers have been telling us “look; we’re not very special”. We used to think that we were the center of the universe of course, and that idea was dispelled quite some time ago. But as we look farther into space, as our instruments are refined and so forth, we find that the sort of situation that we are in, on a cold planet around a rather ordinary star, is in itself, we think, some what ordinary. Planets are a dime-a-dozen in the universe, the miracle of life may not be a miracle, maybe there’s even life near by, perhaps only simple life, but all these developments seem to point in the direction of telling us that biology may be very common in the universe. And maybe even smart biology.

Bob McDonald: Now Dr. Ward, can you give me a quick summary of your ideas before we get into some of the specifics. Why do you think it’s rare?

Peter Ward: Well Seth and I don’t really disagree on an awful lot of these issues. I believe, as Seth does, that life is out there and life just pervades our galaxy, and perhaps, the universe but I think our point of difference may be that Don Brownlee and I think that probably most of it’s microbial, it’s sludge life. But it’s our examination of the fossil record and thinking about some astronomical things as well that leads us to believe that the next step going from a microbe to a bunny, or an animal of any sort, or even a worm, or a plenarea let alone intelligence is exceedingly difficult. And that you need… if life is a nice cake, and if a good cake is an animal, the oven has to be set a very constant temperature for a long time and we don’t think that happens too often.

Bob McDonald: Why not?

Peter Ward: Well, certainly on this planet it took… let’s say we got life on this planet as soon as we theoretically could, about 3.8 billion years ago and then we had to wait another 3 billion years to get animals. And either it takes a long time to build animals, which I don’t believe, or it takes a long time to make an atmosphere conducive so that can live which is probably what happened on this Earth. Our sun is a very large star compared to the rest in this galaxy, only about 10 percent are larger than us, and most of the stars are probably too small. We don’t think that there’s going to be a constancy of conditions that allow liquid water to exist on a planet on most planets. And so we’re really looking at a point of view where, first you have to have an appropriate planet and then you have to have a lot of really interesting but probably low probability things happen.

Bob McDonald: So from an astronomical point of view, if we just look at the number of stars in the galaxy, how do you fell about the rareness of solar systems like ours and planets like the Earth?

Peter Ward: Well I suspect, and certainly Seth knows this, that the planet finding, showing that planets aren’t rare, I mean all of us want to believe that there are planets and now we have actual evidence that there, I suspect that virtually every star has planets going about it. But, maybe it’s not the importance of planets but the stars themselves. And if there are planets, what types of planets are there? We’re not going to exist on Jupiter or Uranus or Saturn, we need a rocky planet. And we need a rocky planet of a pretty good size, because there are certain things about a planet that you also want. You want there to be a magnetic field, for instance. This appears to be very interesting in protecting us from ultra-violet (radiation). You want this phenomenon known as plate tectonics which is a global thermostat. And if you want to have an intelligent civilization arise, you want metal deposits on your surface or near enough. Without plate tectonics there are no ore bodies. You can’t become a radio astronomer without metal.

Bob McDonald: Dr. Shostak, how do you respond to this idea that our solar system and something like that is rare in our galaxy?

Seth Shostak: Well, there’s no doubt that our solar system may be a little bit special, but I don’t think it’s really all that special. To begin with, Peter has said that, well “the Sun is a big star; it’s bigger than 90 percent of all of the other stars in the galaxy”, and in fact that’s true. Let’s just throw out those 90 percent of stars that are a little bit too small. That still leaves 10 percent of the stars in the galaxy, which are very much like our own sun. And that means on the order of 40 or 50 billion just in this galaxy, now to me, that’s a fairly large number. As far as what sort of planets you need? Well, clearly, yes, you want liquid water. Now, I want to point out that water is a pretty common compound. There’s water everywhere. Now mind you, some of it is probably ice, maybe all of it is ice, but it’s not clear that that is true. It seems that there’s an ocean of water on Jupiter’s moon Europa, more water than the Atlantic and Pacific put together. So I don’t think that water is actually very uncommon either. These other sorts of factors, I mean, “do we need plate tectonics?” Well, I don’t know, maybe we do need plate tectonics. All the plate tectonics depends on is that you have a planet that has a little bit of heat on the inside from the radioactive decay of some of the elements that were used to make the thing in the first place. And I think that’s going to be very common.

Peter Ward: People at Cal Tech really don’t think that’s true Seth, plate tectonics maybe very difficult to get. Other aspects that have lead us to our conclusions are looking, and this goes back to Seth’s point, that if we have so many stars of our Sun’s type, then the position in the galaxy is going to affect them as well. We think that closer to the center of the galaxy there’s going to be so many near star passages as we rotate around and around the galaxy in or cosmic merry-go-round, we’re going to come closer to other stars. The closer to the center we are, the more often that happens, when that happens you perturb comets. When comets come rushing in you create mass extinctions. Our planet has had 5 major mass extinctions in the last 500 million years and some would argue that this is a good thing if the dinosaurs aren’t gone then we don’t have this conversation. But let’s say that we had 10 of those mass extinctions instead of 5 or let’s say we had 100 or let’s say we had 10,000. I think very quickly we get to points where you can not have the continued existence of animal life. If we were hit by a 20 to 30 kilometer body tomorrow, you can kiss animals on this planet good bye. And this is the problem about being more centrally located in the galaxy. We think there is a fairly narrow suite of real estate in any galaxy where you can have animal life.

Seth Shostak: Well, I just don’t see that. Yes, we’ve had mass extinctions and sure enough, 65 million years ago the dinos and 50 percent of all species, were wiped out by a big rock from space. But I would complain that our planet has been deprived of these kinds of events. We need more asteroids, because as Peter just mentioned, had we had maybe 10 times as many asteroids as we do now, then the dinos wouldn’t have sat around for 200 million years wasting our time. We’d have the cure for death now if it weren’t for the fact that the dinos just sat on this planet for 200 million years not really going anywhere. So, I’d say a few more asteroids might be a good thing. All you want is that the interval in between major impacts is not short compared to the amount of time it takes to develop intelligence when you can, of course, protect yourself against these things. And, you know, its taken a million years to get humans going. These big asteroids hit every 100 million years, so you could use 100 times as many asteroids and not threaten the development of intelligent life.

Bob McDonald: OK. I’d like to move from our cosmic address here and how much real estate there is in the galaxy to the uniqueness of the Earth itself. What other aspects of the Earth, Dr Ward, do you think make it special that would not happen elsewhere?

Peter Ward: Well, if we wanted intelligence, and we certainly do, it turns out that on Earth if we have temperatures above about 45 degrees centigrade, our mitochondria stop.  We are not animals that can live between zero and 100 degrees Centigrade, we have a very narrow temperature limit. Now this is, again, this is Earth centric. But animal life, at least as we know it on this planet, is very temperature dependant.

Bob McDonald: Dr. Shostak?

Seth Shostak: I’ll agree with that. You need a range of temperature, but it isn’t such an incredibly narrow range. This is what is called the habitable zone. The region from a star within which a planet could orbit where you have, not only liquid water, but liquid water at the right temperatures. But, I again point to Jupiter’s moon Europa. Here’s a situation where you would say, “this is far out in the solar system and it’s really cold out there; there couldn’t possibly be life, let alone sophisticated life”. Well some time in the next 10 or 20 years we’re going to send some ice fisherman to Jupiter’s moon Europa. And they’re going to drill down into the ice. (They’ll probably be robots mind you; probably not people from Wisconsin). They’ll drill down through that ice and drop a video camera or something else down there and it wouldn’t surprise too many scientists if they found some sort of floating complex life in those waters and that, of course would, in some sense, end this argument.

Bob McDonald: Hmmm. I’d like to shift from thinking about complex life to intelligent and technological life. We have lots of intelligent life forms here on Earth but they’re not technological like whales and dolphins. They have big brains but they don’t have machinery. What do you think are the odds of that? Of other creatures on other planets developing technology, that would be technology that could communicate with us, possibly?

Peter Ward: Well I’ve been very much struck by the necessity of metal deposits, and I know I’ve said this and it sounds really boring but I’m a geologist, so bear with me, you have to have metal. You have to be a terrestrial creature; I don’t think an under water civilization could ever arise, but this might be the failure of my imagination, but we have to smelt metal; we have to work up to that; we have to get wires; we have to get electronics. And it’s difficult to do any of that without metal. We have had a series of conditions on this planet that have allowed us to have access to the material that allows us to have radios, or radio signals, or the type of signaling that could leak out of our atmosphere. Could an entirely submarine species do it? I don’t think so.

Bob McDonald: But we’ve had those conditions on Earth for billions of years and yet we’ve only had technology for, what, less that a thousand. Well, not very long anyway compared to the age of the Earth.

Peter Ward: Well it certainly took us a long time to get intelligence on this planet and this is another interesting aspect to the debate. Is intelligence in a species inevitable? Is cephalization going to proceed inevitably towards large intelligence?

Bob McDonald: When you say cephalize you mean big brains?

Peter Ward: Big brains. The dinosaurs never really got very cephalized; they stay around for 165 million years and they had barely larger brains at the end then they did at the beginning. It is not necessarily an inevitable aspect of evolution that we get intelligence. I’m me we get intelligent. Mammals are for more intelligent than worms but could they build radio telescopes? And the answer is no. Steve Stanley and others have argued that there was a series of very improbable coincidences allowing the human sub species, or pre species, pre humans really, to evolve that very large brain; that you had, once again, some improbable events.  Ernst Meyer, Steve Gould and a number of people think that it’s totally unlikely that without those circumstances it would have happened.

Seth Shostak: This is a contentious point. Just because you have life on a planet and you let it sit there and do its’ thing for a few billion years the question is, indeed, how often will it cook up something that’s intelligent enough to build a radio transmitter? And, you know, the jury really is out on that one. I think there’s a lot of debate about that. Let me say one more thing in that regard, maybe we don’t need a lot of intelligent species out there to make the search for cosmic company a fairly easy thing to do. If it’s only happened even a few times in the galaxy, and if that biological intelligence takes the next step, the step that we may take in the next 20 or 30 years, and invents machine intelligence, machine intelligence could spread out. And it may be that the galaxy is stuffed all developed by very few biologically intelligent species some time ago. In other words, machine intelligence.

Bob McDonald: So you’re saying that that our first contact may be with an alien machine rather than with an alien?

Seth Shostak: I think that is not such an unlikely scenario. I wouldn’t be surprised if we picked up a signal from a transmitter and we find that the guy behind the microphone is not a guy, or gal, it’s in fact a machine.

Bob McDonald: Well Doctor Shostak, let me bring you back to Doctor Ward’s basic argument though. He’s saying, “There seems to be a fairly lucky circumstances that lead to our existence and it seems plausible that those circumstances to be very uncommon” now what’s your problem with this idea?

Seth Shostak: Well, this line of argumentation kind of reminds me of when I was back in school my roommate was looking for a date and he lamented are a million women in this city and I can’t seem to find a date. And I said “The trouble is that you’re asking for something very special” I mean “You want them to be between 18 and 25, that knocks out 90 percent of them so that means only 50,000 women”. “And then you want them to be single and that brings it down to 20,000” “The you want them to be good looking and that brings it down to 2,000” “Then you want a high I.Q. and that brings it down to 200” And inside of a minute it turns out we could recon that his requirements meant that there wasn’t a single woman in this entire city that met those requirements, none the less, next week end he had a date.

I think that if we can look very hard at our solar system, our planet, even our sun and see very peculiar things about it but I think what I believe is incorrect is to say “Because it’s got it’s own personality; because our system has all these peculiar characteristics, it is some how very finely tuned to complex life” I don’t that that it’s the case. I’d like to hear from Peter “What factor he thinks is a real show stopper? What characteristic does either our planet or our solar system or our sun have that no other systems in the galaxy would have?”

Peter Ward: We’re not looking at unique, what we are looking at is a series of elements, a series of factors of a low probability each multiplied one by the other that vastly reduces the possibility of intelligent life in the universe. We don’t think that we’re going to find a million civilizations, or even a hundred thousand civilizations, or perhaps even ten thousand civilizations, maybe not a thousand civilizations. Maybe [if] we have between ten and a hundred within our one hundred thousand light year wide galaxy, we’d [be] lucky. And once there spaced out, once we have so few, the possibility of talking to them is low. Do we stop SETI? No. Hell no. I think we have to look. Personally, I paid my money for SETI [and] I want us to look. But do I think we’ll find anybody? I think no.

Bob McDonald: What’s it going to take to answer this question one way or another?

Peter Ward: First! First! Mars! Let’s go to Mars right now. First!

Bob McDonald: Seth?

Seth Shostak: Obviously going to Mars. The thing is I suspect that Peter may be right about Mars. I suspect the Martians are going to be very small and very stupid. And mainly they’re going to be microbes. I have greater hopes for Europa. Europa has been an ocean sitting there for as far as we can tell, three and a half billion years and it may have cooked up something as smart as a tuna, who knows? I think that that would be interesting. But, you know, in some sense it’s going to be impossible to prove that intelligence is rare or complex life is rare in the universe. I don’t know how you would prove that. But what you can prove, and what we hope to prove, is that that’s not true. By finding another civilization or another intelligence if you will because who knows if it’s another civilization, by finding that then we have disproved the hypothesis that we are indeed the smartest things in the universe. Something that many people would love to believe but I find difficult to swallow.>

Bob McDonald: Doctor Ward, why does it matter if we’re rare or not?

Peter Ward: One aspect of the rareness deals, I think, with the number of species that are endangered on this planet. If we’re correct that we are not alone but certainly rare in terms of this animal life, then that raises the issues of extinction and our stewardship of this planet to kind of new levels. That makes us so much less disposable as a planet; it gives us a sense of our place in the cosmos.

Bob McDonald: Doctor Shostak and Doctor Ward, thank you very much for speaking with us.

Seth Shostak: It’s been a real pleasure.

Peter Ward: Thank you for having us.

Bob McDonald: Doctor Seth Shostak is an astronomer with the SETI institute in California and Doctor Peter Ward is a paleontologist at the University of Washington in Seattle. “Rare Earth” by Doctor Ward and Donald Brownlee is published by Copernicus Books.

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