Science Talk

Are There (Microbial) Aliens On Earth?

In this episode, theoretical physicist, cosmologist and astrobiologist Paul Davies ponders the question of whether life originated more than once on earth, and how to find examples of a second origin if it did. Plus we'll test your knowledge of some recent science in the news. Websites mentioned on this podcast include: or;;;

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Steve: Welcome to Science Talk, the weekly podcast of Scientific Americanfor the seven days starting December 12th. I am Steve Mirsky. This week on the podcast: Are there aliens already living among us? We'll talk to renowned researcher and writer, Paul Davies about that. Plus, we'll test your knowledge about some recent science in the news. Paul Davies is a theoretical physicist and cosmologist who has, in the last few years, worked on the problems of the origins of life and evolution. Born in England, he worked in Australia from 1990 to 2006, when he came to Arizona State University to establish an institute called BEYOND: the Center for Fundamental Concepts in Science. He has the cover story in the December issue of Scientific American, called "Are Aliens among Us?" To find out more I called him at his office at Arizona State.

Steve: Dr. Davies, great to talk to you today.

Davies: Hi Steve!

Steve: This is a fascinating kind of thought experiment at this point; actually it's more than a thought experiment, but let's talk about this idea of aliens among us, and by aliens—why don't we talk first about what we actually mean by aliens?

Davies: I'm not referring to the UFOs, the little green men or anything of that sort. By alien life, I mean life as we don't know it. It doesn't necessarily even mean that it comes from beyond Earth, although it might, and in fact it is increasingly fashionable to conjecture that life as we do know [it] may have originated somewhere else, for example Mars, and come to Earth later. But you don't have to buy any of that to understand the basic idea, which is that if life has started more than once, then there is more than one form of life; and it's possible, though a wild speculation, that an alternative form of life might exist all around us, forming a sort of hidden biosphere.

Steve: You have this wonderful phrase "shadow biosphere" in the article, and let me just quote one line from the article that I thought was really great: "At first this idea might seem preposterous; if alien organisms thrived right under our noses or even in our noses, would not scientists have discovered them already?" So it's even possible that living on or inside of us are microbes from a separate origin.

Davies: That's right! So the first thing to understand is that almost all life on Earth is microbial. We notice the elephants and the kangaroos and the big things, but when you take an inventory of all of the different forms of life, then overwhelmingly they are microbes. But now among those microbes it's really impossible to differentiate by looking at their genomes. So you have to sequence the gene to see how they differ. You can't tell just by looking; I mean, some of them are of course like rods and some of them are like little globs and so on, but its not like you can classify them by going to a zoo, and the zebras, you know, it's different from a crocodile. And so it's only when you get into this sort of a genetic study that the possibility opens up that there could be microbial life which we might—in nature, people might have seen these things on the microscope. So this would be microbial life that would not be our life, that it would not share our biochemistry, with difference in some fundamental way, in a way that suggests that it has descended from a different origin. This way it just raises the whole question about the origin of life, the ultimate genesis of life and whether it happened once or happened many times.

Steve: Right! And that's a key idea of the article, is that to just see how natural an aspect of an environment the advent of life is, we don't necessarily need to investigate the rest of the solar system or the rest of the galaxy.

Davies: Yes, the origin of life is one of those great unsolved problems of science that people love to think about, and it's fascinating that Charles Darwin gave us the theory of evolution nearly 150 years ago, but he pointedly would not be drawn on how life got started in the first place. He in fact cribs that one might as well speculate about the origin of matter, so he just assumed that, you know, by some sort of magic life existed and then started to evolve. But the question about how does life form from nonlife, of course, has been a preoccupation of scientists ever since, and we made a little bit of progress on it, but not a great deal; it's still a great mystery, and it tends to divide into, the when, the where and the how. As far as life on Earth is concerned, we've got a pretty good idea that it was well established by about three and a half billion years ago. So whereupon people argue about and my end point of view is that where life started on Earth, I favor the hot location, maybe in the Earth's crust or on the seabed or possibly it came from Mars, maybe it formed on Mars and came here later, that's another conjunction [conjecture]. But the how part is the one that really nobody can agree on. There are biologists who has [have] said that life is so complex, even the simplest living thing is so stupendously complex; but if it's formed by the chance shuffling of molecules, it has surely happened only once in the observable universe. It would be like a freak, an aberration and this is it; we see it around this, and so that's all there is; that we couldn't expect there to be life anywhere else. And then, at the other extreme, there are biologists, for example, like Christian de Duve, Noble Prize winner, who says that "life is a cosmic imperative" is the way he expresses it; that it's written into the fabric of the universe in some deep way, and it will emerge wherever there are Earth-like conditions. And so we['ve] got this vast spectrum between, "Life is just a stupendous fluke, happened only once" to the other end, the astrobiologist's end, that "it's going to pop up all over the universe." Well how do we test that? How [can]come we answer the question, Is life expected? Is it something that would arise readily in Earth-like conditions? Or is it exceedingly rare, maybe unique, maybe just confined to Earth? And now the obvious way, the direct way, is [to]it go somewhere else; go to another Earth-like planet, see if life has started to scratch there. The problem is that the most hopeful planet within the solar system, which is Mars, is already compromised; and the reason for that is that Mars and Earth have throughout their entire lifetime having been trading rocks in very large quantities—I think it's pretty well known now that there are Martian meteoroids in collections here on Earth. So the famous one that Bill Clinton told the world about when he stood on the White House lawn and said that NASA had evidence for life on Mars from marks in a meteoroid found in Antarctica that comes from Mars—but I think that turned out to be wrong but nevertheless—we now know that Mars rocks come here and Earth's rocks go to Mars. But because rocks are a very good place for microbes to live—we know that just by looking inside Earth's rocks, that [which] are teeming with microbes—that this is a great way they can be conveyed from one planet to another. So these rocks get blasted off by asteroid and comet impacts and fly around the solar system, and they can cocoon microorganisms that could be protected from the rigors of outer space, and eventually they are likely to land on another planet. Earth and Mars look like, they have cross-contaminated each other throughout their history, so going to Mars and finding life there probably is going to settle the issue. Going to, well, I think probably outside of the solar system altogether to an Earth-like planet in another star system, before those there is negligible risk of cross contamination, and we are not going to do that anytime. So it seems to me that meanwhile all we have to do was [is] to ask the question, "What if life really does form readily in Earth-like conditions?" The most Earth-like planet we know is the Earth itself. Shouldn't it have happened many times over right here on our home planet? And if indeed, if life started more than once on Earth, what would we look for? What sort of evidence might there be of multiple origins of life? So that's the starting point in this series of conjunctives, the research program [as] I like to say it.

Steve: Let's talk about the problems inherent in looking for this needle in a stack of needles. So you talk about going to extreme environments or extreme conditions to try to find something that might stand out.

Davies: Right! Now about a year ago, we held a workshop at the BEYOND Center here at Arizona State University where I brought together a number people working on searching for organisms in extreme environments and searching for novel forms of life elsewhere in the universe. And we put our heads together to try to decide what was the best way we could identify alien microbes, if they are indeed here on Earth. And we figured that there were really two quite distinct circumstances. One is if the alien microbes were ecologically separated from known life, that is to say, that if life has started many times over, perhaps some life likes it hot, some life likes it cold and so on; and that we could look for extreme environments on Earth which are beyond the limits of known life. Known life of course can exist in a wide variety of circumstances—very harsh conditions such as extreme cold or heat, extreme acidity, or saline conditions; and we still find living organisms there and when you sequence their genomes you find that they are life as we know it. Yet there must be some outer limit to what known life can endure. For example, if the temperature is raised, you find organisms living in deep oceans, volcanic trenches, that are quite happy to metabolize at up to about a 120 degrees centigrade, maybe even a little above that. But surely there's going to be some limit that they can figure say, 135 centigrade, beyond which known life could not survive. Now if then we found some thing living at 180 centigrade, then that might well be life as we don't know [it]. So we could look in these extreme environments to see if known life reaches out, and then there is a gap and then we see some other form of life resuming; and we could apply that for any of the parameters, whether dryness, radiation exposure, pressure and so on. And so we are then looking for a niche ecology that could be occupied by some exotic weird alien form of life. Well that's scenario number one—ecologically separated. In many ways more fascinating is how then to get that group straight, is to ecologically integrate; that is to say, we are dealing [with] a different form of life, but it is perfectly happy to kind of inhabit the planet with us in a similar type of environment, so we could imagine that there might be alien microbes all around us. As I think you have quoted earlier, "under our noses or even in our noses" and this is a case of peaceful coexistence. People will often say, "Oh! Well if there was some other form of life on Earth, another form and that form will be sort of fighting for resources, and they will be in competition, and one might eliminate the other." But I have never been (unclear 12:31) [convinced] by that argument. We know even just within life as we do know it, that the archaea and the bacteria—these are both microbial realms—they are very different from each other, but they don't eliminate each other. They peacefully coexist. So, it seems that we could have microbial life, but need some of the same sorts of things, you know, for example carbon and liquid water. But there wouldn't be any direct competition so that one eliminates the other; they would live along side each other, but they wouldn't swap genes, for example, because they would be sufficiently different. They couldn't you, know, talk to each other biochemically, and they would just occupy similar habitat. Another question is, "How come [can] we tell that if we just take a sample of microorganisms from, you know, soil or somewhere else and just look at them under a microscope?" Well, of course, there is a huge number and a huge variety; it's going to be very hard to tell that way. So we would be looking for some exotic type of biochemistries and then the question is what? And there is a sliding scale of things that could be different. For example, we might imagine that another form of life would be based as is ours on nucleic acids and protein, but they may be different proteins, they may be made up with different amino acids from the ones that we use. And so one possibility is to simply look for organisms that have got a different complement of amino acids, at the time that they might be doing things differently. And then one can push that scale of difference to the point where we might consider one of the essential elements of life, as we know it, which is we have carbon, nitrogen, hydrogen, phosphorus, oxygen, and sulfur. We take those elements and consider what would happen if one of them was replaced by something else; and one in particular that we discussed at length at the workshop—on which I have been developing, you know, a research project here at ASU—is that maybe phosphorus, which is a rather rare element on Earth, might be in a different form of life, be replaced by something else—the something else we are looking at is arsenic. Arsenic is a poison, precisely because it mimics phosphorus chemically in many ways, but then it has differences too, and so is it possible that there is some sort of arsenic life out there in the environment? And so we've been thinking about ways in which we might identify arsenic life: Where it might be living? What it might be doing?

Steve: Let me ask you a nuts and bolts question. How, does a graduate student or a young faculty member who has to apply for funding convince the parties they have to convince to do this kind of research?

Davies: Well, it's always the case with cutting edge research, particularly we are pushing the conceptual boundaries; but it's hard to get funding from mainstream agent. The good news, however, is that you don't need very much funding to look over a sort of thing that we've been discussing. So let's take, for example, "Are there organisms that use arsenic instead of phosphorus?" Well you might think, "Let's go somewhere which is rich in arsenic and poor in phosphorus," and one place we've identified is precisely the ocean vent. On the seafloor where you have these volcanic vents that discharge fluids into the surrounding seawater and form the circle black smoker which is very famous from all sorts of mazes that have been made about the static ecosystem around there, well we think that some of these will be rich enough. They can then be a great place to sample microorganisms. Now these systems are being studied anyway. People are sending submarines there. They are extracting bits of these black smokers, they are studying the microorganisms there, so it's not like you've got to have a special expedition; and it's certainly, even if it did, certainly a lot cheaper than going to Mars to look for exotic lives. And so really it's a matter of forming the necessary collaboration for people who are studying life in exotic environments and making them available to researchers who might be interested in seeing if there is something different. Now you see that the problem that happens if you talk to microbiologists about, have they ever come across microorganisms, they just bent in to fit the bill as far as their customized techniques are concerned; well of course, all the time, if they will, they couldn't culture these organisms or then couldn't sequence them, and then you know they are just difficult to work with. And you ask them: "What do you do with them?" They say, "Well, we throw right away, we go onto something else," and so, you know, the techniques which are developed to study life as we know it are all very refined, but they only work with life as we know it. So, we are looking in a sense at the stuff that gets discarded, that there may well be microorganisms in labs around the world in collection. They all are simply organisms that are just intractable; they won't behave themselves when being studied by conventional methods. Let's look again at those, let's see if there is anything that this is not responding to the sort of customized biochemical procedures and look more carefully with not very expensive equipment to see if there is something different in inside them.

Steve: The ultimate junk DNA.

Davies: Yes, yes that's right. You see, if they could be DNA-based organisms, then we will find that the usual triplet code isn't going to work for them, and the sequences that codes the genes of the sort that we know are simply not going to be coding. Now we have also the possibility of organisms that would use not just different genetic code, but different numbers—instead of being a triplet code, maybe doublet code which would be simpler; and again these working will [not] show up with the sort of the techniques people are using in known life, but when specifically looking for doublet code, well then it might well be that we find such a thing.

Steve: What do you think the psychological effect would be from finding something that was verifiably from a different origin?

Davies: I think it's really, really profound. If you ask people, "Should we be going into space and what are we doing there?" and, you know, "What is the purpose of NASA itself?", the general public overwhelmingly thinks that the reason for going into space is to seek out other forms of life. What they are really fascinated by is to answer the question, "Are we alone in the universe?" And, you know, much is that[as] it's great to see the pictures of the giant planet and so on, I think it's the prospect that we are not alone and that there is other life out there somewhere that really fascinates them. And the issue here is a very profound one, because if it turns out that life is just a freak phenomenon, if it is something that has just happened against all the odds in one little corner of the universe, and it is indeed, the philosophical implications of that are pretty profound. We are alone in the universe, we must take better care of our planet, of course, but it means that in some sense you know life is just a quirky phenomenon and it's not really built into the great cosmic scenery, but if conversely it turns out that the universe is intrinsically bio-friendly, if life emerges all over the place as part of the natural outworking, so it's an inherently bio-friendly universe; well that's the universe that I prefer by temperament. It makes me feel at home in the universe. I think, well, we are not just freaks; we, in a sense, belong here, and that's a very, very profound thing. Now if we find that life has started many times over on Earth, well, then we know that it would have formed all around the universe, because if it is a fantastic and improbable thing that [then] the chance of [life] happening twice here and nowhere else are infinitesimal. So we know that if life has formed many times on Earth, or even just more than once, so it's just formed twice on Earth, then we know that the nature really is intrinsically bio-friendly. We know that life is what Christian de Duve calls, "a cosmic imperative" and we expect to find it everywhere, we won't be alone in the universe; and that completely changes the way we see ourselves in our relationship to the nature. So the consequences I think are very sweepy [sweeping]. It's not just a technical, scientific thing. It's something that holds very, very deep philosophical appendage.

Steve: Its great stuff. "Are Aliens among Us?" is the title of the article by Paul Davies; it's in the December Scientific American. Paul, really fun to talk to you. Thanks very much.

Davies: Thank you for your interest.

Steve: Paul Davies's article is available free at our Web site. Just go to For more on Davies' Center for Fundamental Concepts in Science go to By the way, the deputy director of the center is geologist Kip Hodges, who appeared on the July 26, 2006, episode of this podcast, still available at our Web site. Paul Davies' latest book is called Cosmic Jackpot: Why Our Universe is Just Right for Life.



Story number 1: City dwellers are less likely to go skiing when their own backyards are bare, even if ski resorts have lots of snow.

Story number 2: Gila monster saliva is the source of a promising new diabetes drug.

Story number 3: A survey found that the vast majority of parents of obese kids between six and 11 were "very concerned" about their kids’ weight.

And story number 4: Research just published that looked at the experience of time passing involved volunteers plummeting 10 stories into a net.

Time is up.

Story number 1 is true. New England urbanites go skiing less if they don't see snow at home, even if the snow at resorts is deep. That's according to research out of the University of New Hampshire that was published in the December issue of the International Journal of Climatology. The researchers studied two New Hampshire resorts and found that attendants [attendance] more strongly depended on whether it snowed in Boston.

Story number 2 is true. A drug derived from Gila monster saliva increases the amount of insulin the pancreas secretes. For more, check out the special report "Managing Diabetes" in the new Scientific American Body magazine at

And story number 4 is true. The study of time perception did involve dropping people into a net from 100 feet. The researchers wanted to find out if time really does seem to slow down in a crisis and the study subjects did estimate their own time spent dropping as taking a third longer than their estimates of other people doing the same thing. But the falling subjects were not able to distinguish numbers moving fast on a meter any better while time seemed to be slowing down to them as they were falling. So forget about dodging slow-moving bullets there, Neo.

All of which means that story number 3, about how most parents of obese kids are worried about their weight is TOTALL……. Y BOGUS. Because [a] University of Michigan survey of parents of obese kids six to 11 years old found that only 7 percent of parents with kids in that age group who were obese were very concerned about their children's weight; more than 40 percent thought that the kids were at "about the right weight".

Some important notes: Last week on the podcast, we talked about honey replacing cough suppressant for kids, except you should not use honey with kids under 12 months of age, because infants that young are at risk for a rare form of botulism from honey. The bacteria involved are typically harmless to older kids and to adults according to Thanks to listener, Joshua Miller for writing in with that.

Also on the November 21st podcast, we talked about cheese and cheese researchers Carroll Chen said:

Chen: Cheddar cheese versus Limburger cheese versus Mozzarella versus Jussto Liepa—they all have the same ingredients which are ...

Steve: Well, what was the last one?

Chen: Jussto Liepa

Steve: What's that?

Chen: It is a Finnish bread cheese.

Steve: Well, listener Diana Kuzminer wrote in from Helsinki Finland, where she is a geneticist for the National Health Institute to say that "the cheese which I tasted—and it is really delicious—is actually pronounced Jussto Liepa"; and I hope I pronounced Kuzminer right.

Well that's it for this edition of the weekly SciAm podcast. You can write to us and check out numerous features at the new Web site, including articles from the new Scientific American Body magazine, which looks at the science behind health; that's at For Science Talk, the weekly podcast of Scientific American, I'm Steve Mirsky. Thanks for clicking on us.


Add Comment
  1. 1. terry.cockburn 09:00 PM 12/14/07

    Fascinating to consider that rocks could or can carry microbes across space from planet to planet. And, I suppose, it would be possible to it to happen from star systems to other star systems.

    Reply | Report Abuse | Link to this
  2. 2. ggmmss 07:22 AM 12/16/07

    I am true there is. Because I believe everything has to be balanced, so does human.

    Reply | Report Abuse | Link to this
  3. 3. Larry Wampler 12:44 AM 3/14/08

    I have your alien life in my yard. A green circular growth with about 3 inches diameter and 1/2 inches (12 mm) thickness. Has rows of something that looks like leg buds. Never seen anything like this before. It has been cold (20s F) for such a thing to grow this past winter. 3/13/08... I have a picture also.

    Reply | Report Abuse | Link to this
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