If we want to test the idea that life forms easily in Earthlike conditions, why not search for organisms outside our tree of life—right here on Earth?

Question: What new kinds of evidence of alien life might we search for?

Paul Davies: It seems to me that the most obvious thing that we can do to test this idea that life does form readily on Earth-like conditions, an idea incidentally that Christian de Duve, who is a famous biologist, has called the cosmic imperative, this sort of wonderful phrase, so how do we test the cosmic imperative?  What we want is to find a second sample of life.  What Chris McKay at NASA Ames calls "life 2.0."  We’ve got life 1.0.  Here it is.  What we want is another sample of life, which is not on our tree of life at all.  All life that we’ve studied so far on Earth belongs to the same tree.  We share genes, for example, with mushrooms and oak trees and fish and bacteria that live in volcanic vents and so on that it’s all the same life descended from a common origin.  What we want is a second tree of life.  We want alien life, alien not necessarily in the sense of having come from space, like it might have done, but alien in the sense of belonging to a different tree altogether.  That is what we’re looking for, "life 2.0." And one place we can look is right here on our home planet.  No planet is more Earth like than Earth itself, so if life really does pop out readily in Earth like conditions surely it should have arisen many times over right here on Earth.  How do we know it didn’t?  Has anybody looked?  Remarkably enough until a few years ago nobody thought to look for a second sample of life on Earth.  Everybody just naturally assumed that all life on Earth is the same life.  Well as I’ve said all life so far studied is the same life, but we haven’t studied all the life there is. 

Most life on Earth is microbes.  We notice the big things.  We notice the trees and the elephants and so on because they’re big, but the vast majority of species on Earth are microbes and we’ve only just scratched the surface of the microbial realm.  Probably less than .1% of microbes have been classified let alone cultured or had their genes sequenced, so really that microbial realm is a mystery.  We don’t know what those little bugs are and it’s entirely possible that intermingled among the microbes that are related to you and me are some microbes which are not on our tree of life at all.  They would be genuinely alien life.  Life 2.0 could be right under our noses or even up our noses, so I think the most important way we can advance this quest for ET is to look right on our home planet to see if we can find a second sample of life and I’m working with people to do just that.

Question: How hard are we looking for simple, as opposed to intelligent, alien life?

Paul Davies:  Almost all the effort that is expended in astrobiology is towards looking for simple forms of life.  Usually just microbes and microbes on Mars would be our best hope.  Then we know that within the solar system is very unlikely there will be anything  more advanced than microbial life, but if we think outside the solar system and then the distances are of course immense then there could be Earth-like planets with more advanced form of life.  For example, there could be photosynthesis that’s going on that would leave a signature in the form of oxygen in the atmospheres of these planets.  Now it’s the only the last few years we’ve discovered any planets outside the solar system.  There is a list of about 450 now and there is a satellite called Kepler, which is going to find a lot more over the coming year or two. And then we’ll have a shopping list of likely planets, maybe Earthlike planets, where future instruments that will be very expensive and very technically very challenging, but nevertheless, could be built in decades hence.  These instruments could then scrutinize these planets that we’ve found and see if it can get enough information about their composition of their atmospheres to say they may have life.  Of course again it would be an indirect signature of life.  We wouldn’t be seeing the life itself, just its byproducts, say, in the form of oxygen.

So these are the best hopes, but of course I think from the public’s point of view they’re less interested in microbes or plants.  They’re much more interested in intelligent aliens and so the search for intelligent, extraterrestrial intelligence, intelligent aliens or advanced alien civilizations, something like that is in the province of the SETI program and they look set to continue doing more of the same for the coming years.  They’ve got a better system.  The Allen telescope array in Northern California has been paid for in part by Paul Allen, the co-founder of Microsoft and this is currently under construction and when it is finished it should have 350 dishes, which hooked together will form a telescope with a very large collecting area.  It’s a radio telescope, so again, it’s listening for radio waves from ET, but I think meanwhile we should broaden the search and start looking for other things.  For example, even in radio we should be looking for beacons as well as so called narrow-band signals.  The way that SETI works so far is that they tune into the heavens a bit like you tune into your local radio station, that is that there is a particular… they’re looking for a particular frequency, a continuous transmission at some sharp frequency, which is the way we do it, we’re sending messages here. But there is another type of message which is in a way it’s like the message in the bottle.  It’s a one-way message.  It’s a lighthouse is a good example of that.  It just sends out a flash for anybody who may or may not be out there, who is looking.  In the same way we can imagine that some alien civilization may be be long vanished, has made a beacon that is sweeping the plane of the galaxy and it would just something that goes bleep in the night.  You’d hear this bleep that is ET pinging us.  You maybe wait a few months or years and it would ping us again and if you hear enough of those pings you would sit up and pay attention. 

The SETI program is not well geared up for the pings.  They’re trying to diversify their technique so they can search for such things, but it really needs a more expensive system of dedicated instruments, radio telescopes that stare at some particular patch of sky for months or years on end just so that you see the repeat of these pings, so at the moment if a radio telescope picks up a ping, a transient pulse of some sort what can you do?  You can shrug and say well it was some strange pulse came from over there.  There is nothing you can do about it.  It has been and it’s gone.  You can’t get somebody else to observe it because it is all over and there have been many examples of recorded transient events of that nature.  Nobody knows what they are.  They could have natural explanations or maybe these really are beacons.  We shall have to wait and see.

Recorded April 15, 2010
Interviewed by Austin Allen