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Practice English Speaking&Listening with: Paul Davies on the Origins of Life

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[ Applause ]

>> Well, thank you, Ann, for that kind introduction.

Ladies and gentlemen, good morning [inaudible].

It's great for me to be back here in Sydney Upper House.

It's also great for me to catch

up with my colleague, Lawrence Kraut.

We have adjacent offices at Arizona State University,

but we both travelled so much

that we're often not there together.

So it's nice to be in the same place for once.

Now, a pivotal event in the history of science occurred

in the year 1859, with the publication by Charles Darwin

of his famous book, "The Origin of Species".

And in his book, Darwin gave a convincing account of how

over billions of years, life on Earth had evolved

from simple microbes to the richness and complexity

of the biosphere that we see today.

But he pointedly left

out of account how life got going in the first place.

"It is mere rubbish," he said, "thinking of present

of the origin of life.

One might as well think of the origin of matter."

Well, I'm pleased to say that we physicists have explained the

origin of matter; Lawrence mentioned that.

And the question is how we are getting

on explaining the origin of life?

Well, I have to say that a century and a half later,

we are still largely in the dark about life's origin.

Now, the problem of life's origin is really three problems

rolled into one.

There's the when, the where, and the how.

And I'll talk about each of these in turn.

First of all, when did life begin?

Now, we can't say exactly when it began,

but what we can do is trace the fossil record back in time

to the earliest point where we can be fairly sure, that is,

we look for the oldest traces of life on Earth.

And it turns out that those oldest traces are found right

here in Australia.

Well, not quite here, but on the other side of Australia,

or the Pilbara region; that's near Port Hedland.

And in that region, there are rocks that are sticking

out of the hillside, which are three-and-a-half billion

years old.

So they're among the oldest known rocks on Earth.

And those rocks contain what is probably the oldest traces

of life on Earth for the generally-agreed.

There's some dispute that are rocks a bit older than that,

but there's some dispute

about whether the traces of life are genuine.

But those particular rocks, we're pretty much agreed,

do contain evidence for life.

But this evidence is in an indirect form.

So I took a travel to go there back in my moustache days,

[laughter] and it's best not to go in the summer.

It's actually very hot in that part of Australia.

And this is what the scientists get excited about,

this rock here; it's called "chert".

And if you look carefully in that chert,

what you see are these little features,

they're like ice cream cones nested together

and sliced through.

Now, I have to say that doesn't look very exciting to me,

but the astrobiologists --

they're the people who study life in the universe,

they get very excited by these features,

which have the name "stromatolites".

Now, true technically, they're not stromatolites,

they're fossilised stromatolites,

three-and-a-half-billion-year old structures.

And they're not themselves --

were never themselves living things.

They're fossils of microbial mats,

so microbes that deposited sediment in layers

over many thousands of years,

and then these things became fossilised

and embedded in the rocks.

And that's what gets them excited.

Now, you might say, "Well, show me a living stromatolite."

They're very rare.

It's hard to find stromatolites, but you can.

If you're visiting the Pilbara Region, I do recommend it.

Then a couple of days' drive from there, you go to Shark Bay,

and there you see living stromatolites.

[Laughter] And you see --

what I like to say is if you imagine getting

in a time machine and going back three-and-a-half billion years

on Earth, this is as good as it gets.

You know, this is life on Earth.

That's about all you see.

It's really, really boring.

So it took a long time for life on Earth

to evolve the complex structures like us.

In fact, for about two billion years, there wasn't much to see.

And so it's not very exciting,

but it's tremendously significant that we see fossils

of structures like this in these very ancient rocks.

So it looks like life was established on Earth,

quite firmly, three-and-a-half billion years ago.

Now, let's put that into context.

The Earth itself, the solar system indeed,

is four-and-a-half --

little over four-and-a-half billion years old.

And of course, it didn't formed overnight.

The planets form from a swirling disc of gas and dust

around the protosun, and it took really quite some hundreds

of millions of years for this process to be completed.

And during that time, huge chunks of material rained

down on the newly-formed planet.

So this is a NASA depiction of this process;

and here's another one.

We can imagine the early Earth being bombarded ferociously --

[inaudible] all of the early planets bombarded ferociously

by huge comets, and asteroids, and rocky bodies.

Now, I'm sure everyone's familiar with the fact

that the dinosaurs were probably done in by a comet that smashed

into Earth about 65 million years ago and created a crater

about 180 kilometres across in what is now northern Mexico.

Well, that was small-scale stuff compared to what was going

on in the early time in the solar system.

The biggest of these impactors would have had enough energy

to boil the oceans dry, and sway their planet

with incandescent rock vapour.

And so this is an artist depiction of this sort of hell

on Earth that would have persisted --

it's a little hard to know, but certainly

for some hundreds of millions of years.

And in fact, the best record of this early bombardment comes not

from Earth itself, because the material gets reprocessed,

but from the moon.

And on the moon, all those craters that are so familiar,

tell us something about the early heavy bombardment.

And if you put some sort of schematic graph,

what you find is that this bombardment abated

around about 3.8 billion years ago, whereas as I've told you,

life on Earth extends back through 3.5.

Of course, it didn't appear overnight,

so presumably back to, you know, at least 3.6 billion years ago.

And so this is a very narrow window.

In fact, Carl Sagan many years ago said that life must be easy

to get going, because no sooner was Earth ready

for it than up it popped.

Turns out that that argument is fallacious.

It might be right, but it doesn't have to be.

So I'll come back to that.

But the important point is that there's been life on Earth

for almost the entire duration of when Earth has been habited.

Okay; let me come onto the where part.

Where exactly did life start?

[ Silence ]

Well, I mention that Darwin wouldn't be drawn

on the subject of life's origin.

But in an effort to refrain, he did speculate

about what he called a "warm little pond" over which

over many millions of years chemicals might leach

out of the rocks, and by some sort of process

of chemical self-assembly,

more and more complex molecules might form,

until eventually something would crawl

out of this warm little pond.

And that's as far as he would be drawn.

But it did give rise to the popular notion of some sort

of primordial soup, at least an aqueous medium

in which some sort of chemical magic might take place.

But we don't quite know what that magic is.

So is this warm little pond idea a viable one?

Well, really I have to say that it's not.

Remember this hell on Earth,

so this early bombardment would have meant

that warm little ponds wouldn't really have survived

for very long.

And so the attention in recent years have shifted from ponds,

to what is sometimes called the "deep hot biosphere".

Now, it comes to a surprise to people that life

on Earth is not just restricted to its surface.

In fact, the substantial fraction

of the Earth's biomass is actually living inside the

Earth, not on the surface.

Deep down, nobody quite knows how low you can go,

but it's certainly some kilometres.

And of course the organisms that live inside the rocks deep

down are microbes, and they live in the pores of the rocks.

And this is not a very congenial place to be.

For start, what do they do for sustenance?

Well, basically they have to make do with what's there.

And to be honest, it's not so much of the rock,

though the minerals are useful for other purposes.

But there is stuff coming up out of the Earth, like hydrogen

and hydrogen sulphide that acts as the fuel

for this primitive metabolism in these microbes.

And they're still there.

They're still down -- if you could drill down under our feet

for some kilometres, you would find its teeming

with life down below us.

And that seems a safer place to be.

If the Earth is being bombarded, you don't really want

to be anywhere near the surface.

And some evidence that life started inside the Earth,

not on the surface of the Earth, comes from these hot springs,

the base of the ocean, where the lava hits the water.

Basically, there are regions

where the Earth's plates are moving apart,

and stuff is coming out from deep down.

And this hot material when it meets the water,

the water circulates and reaches temperatures of up

to 350 degrees Celsius, squirting out of those jets.

They're often called "black smokers",

because they make black chimneys on account

of the minerals that they deposit.

And what came as a great surprise to biologist

about 35 years ago was the discovery that this region

around these black smokers, is home to a rich ecosystem,

a vast range of microorganisms making a living at temperatures

above the normal boiling point of water.

The water doesn't boil because of the high pressures there.

So making a living at temperatures

above the normal boiling point of water;

and they can support an entire food chain

with invasive species, like crabs and tubeworms.

And now the significant thing is when you sequence the genomes

of the microbes at the base of this food chain,

you find that they're among the oldest

and deepest branches on the tree of life.

You can sort of reconstruct the tree of life

from all the species and work backwards,

and see which organisms have, as it were, changed least

over the billions of years on Earth.

And it turns out to be these critters that live

in these hot spring areas.

And also I think -- in my view,

the surface around these hot springs, although it's deep

under the ocean, is still a hazardous place.

And it would be more likely that life would form even deeper

than that inside the Earth.

But having said all that, all I told you is

that life established itself on Earth

by three-and-a-half billion years ago.

But we don't actually know that life on Earth started on Earth.

It might, for example, have come from Mars.

How could life form on Mars, and then come to Earth?

How is that possible?

The next slide says it all.

That [laughter] same bombardment which pulverised the surface

of Earth, Mars and all the other planets in the early days,

also served to propel material around the surfaces.

And if Mars takes a hit even today by a comet, say,

ten kilometres across, that will splash huge amounts of material

into [inaudible] orbit.

And some of that material comes to Earth.

And it comes as a surprise to people to learn

that there are Mars rocks right here on Earth.

But there are.

Here's a picture of me holding one.

Now, I have to say, it's a bit of a story to this.

This picture -- this rock was collected by Douglas Mawson,

unrecognised for what it is as a piece of Mars.

And it was in the geology department museum

at the University of Adelaide for years and years,

until it was recognised as being of Martian origin.

It actually fell in Egypt some decades ago,

and apparently killed a dog.

And I think that's the only known canine fatality

from a cosmic object.

[Laughter] But in the early days, they were quite relaxed

about this rock and they used to lend it to me.

And I would take it to lectures, and even travel around the world

with it once and would often, you know -- it was in my pocket,

would often forget about it.

But it was always a great topic of conversation in pods.

And so, Oh, it's my round, lads.

"Oh, look, yes, this is a piece of Mars."

You know, and people would be sceptical

of constellation and so on.

But it was always a great thing to have with me.

But now, of course, they realise it's worth millions of dollars,

they don't let it out.

[Laughter] But [inaudible] State University, we have not one,

not two, but three Mars rocks.

Somebody can ask later on how do we know they came from Mars.

I won't get into that.

Anyway, the question of rocks from Mars was propelled

to public fame by none other than Bill Clinton.

This is -- I call this the rock that made Bill Clinton famous,

because he stood on the White House lawn in 1996

and proclaimed that NASA had evidence for life on Mars

in the form of this Martian meteorite that was found

in Antarctica that contained these funny little features

that for a while looked to be

like fossilised Martians, albeit diminutive.

And since then the evidence has largely gone away.

And I think very few people still feel

that this particular meteorite contains evidence

for life on Mars.

But, you know, it's an interesting thought if there was

or is life on Mars, we might detect traces of it

in Mars rocks right here on Earth.

So that's an interesting aspect.

Okay. So much for the where.

Let me move onto the how part.

And this is the really tough part

of the problem of life's origin.

How did life begin?

And I think I can be quite upfront

about this; we haven't a clue.

I mean, we really do not know.

And it's sort of depressing to think we may never know.

We may never have a blow-by-blow account

of how life on Earth got started.

And part of the reason for that is it all happened

such a long time ago.

So even if life on Earth started on Earth,

all traces of the early processes will have been

obliterated a long time ago.

However, I think we would settle for something less

than understanding each step of the process.

We will be content to know simply was it a bizarre fluke,

maybe unique in the observable universe,

or is it a chemical inevitability, that is,

is it bound to happen given enough time?

Now, during my career, it's been very curious,

the pendulum has swung quite decisively.

I got interested in searching for life beyond Earth,

and in particular, searching for intelligent life beyond Earth,

aliens -- I'll come to that in a moment,

back when I was a student in the 1960s.

One might as well have professed an interest

in searching for fairies.

It was a widely assumed that among all the scientists

that life on Earth was a bizarre fluke unique to our planet.

And no person said it better than Jacques Monod.

He said, "Man at last knows that he is alone

in the unfeeling immensity of the universe out of

which he emerged only by chance."

That was in 1970.

Well, I have to say this did coincide with the period

of Gaelic nihilism [phonetic].

And he looks suitably miserable about his pronouncement.

[Laughter] And you might say, "Well, you know,

that was just his philosophy."

But Francis Crick, Mr. DNA, had a similar opinion,

and in 1973 wrote, "Life seems almost a miracle,

so and many other conditions necessary for it to get going."

Well, we scientists don't believe in miracles,

so we've got to do better than that.

And so that idea that life is a sort of a fluke, we are freaks,

it's a bizarre aberration in the universe,

that feeling seems to have changed.

And so in more recent years,

there have been much more upbeat comments.

So here's one by Christian Verdu [phonetic],

a Nobel prize winning biologist, just like Francis Crick,

drawing a very different conclusion.

He says, "Life is almost bound

to arise wherever physical conditions are similar

to those of the Earth."

That was in 1995.

And he's got this wonderful phrase that,

"Life is a cosmic imperative."

And so the question is, "What is the case?

Is life a bizarre fluke, or is it a cosmic imperative."

I get infuriated, because very often get asked by journalists,

"How likely is it that we would discover life

out there beyond Earth?"

And I say, "The question is meaningless."

It is meaningless for a very simple reason,

that many of my distinguished scientific colleagues seem

to forget about.

Okay? How did life begin?

If we don't know the process that transformed nonlife

into life, we can't possibly estimate the odds

of it happening.

You cannot put the betting odds

on a process that you don't know.

If you know the process, even if you can guess the process,

you can have a stab of figuring out how likely it is.

But as we don't know what that process was,

we absolutely have no clue.

We can say nothing whatever about the likelihood

of life starting, which is the same as the likelihood

of life beyond Earth, absolutely nothing.

Now, there's no lack of real estate

on which life may have arisen.

And so this is a satellite, Kepler,

now sadly not operating correctly.

It's been up there in space.

It's a NASA mission, and it's been looking

for extra solar planets, that is planets going

around other stars.

When I was a student,

nobody could be sure there were any planets going

around other stars.

Now, there's a catalogue of hundreds, if not,

a couple of thousand of candidate objects.

And these objects -- the planets tend to be

on the whole much larger than Earth, but the holy grail is

to discover Earthlike planets going around sun-like stars.

And the statistics of this process are now good enough,

though one can have an estimate of how many Earthlike planets --

depending on a little bit on how you define "Earthlike",

how many Earthlike planets there are in the galaxy.

And this is a typical report you'll be very familiar

with this sort of thing.

I'm sure any of you who are following [inaudible] will have

picked up this, in my view, ludicrously upbeat assessment

of the likelihood of life beyond Earth.

There are billions of Earthlike planets in our galaxy.

And the keyword here is billions, or tens of billions

in this case, of "habitable planets".

And people think, "Oh, tens of billions of planets with life."

What they forget is that

"habitable" does not mean "inhabited".

They sound the same, but they are very, very different.

Just because a planet could sustain life

of the form we have here on Earth,

doesn't mean it's going to have it.

A habitable planet becomes an inhabited planet,

if and only if, the probability of nonlife turning

into life is quite high; is not incredibly small.

But we don't know that, because we don't know what the

process was.

So let me just stress [inaudible].

If there's any take-home message from this lecture,

is it that we do not know how nonlife turned into life,

so we can't estimate the odds.

Now, we can hope, if like me, interested in the idea

of life beyond Earth since being a teenager, if you feel like me,

then you will hope that there is a fast-track pathway

from nonlife to life.

You may hope that there's a life principle in the universe,

this law of nature that says, "Given the matter,

given an energy source,

given enough time, then life will out."

You may hope there is such a principle.

I hope there's such a principle.

But we haven't yet discovered it.

There is no known such principle in physics or chemistry.

We haven't found a life principle.

We could believe that it is an act of faith,

that it might be that; but we haven't found it.

So we must contend to the fact that it could be

that life is restricted to Earth, maybe it's splashed

around a bit in the solar system.

But it could be that we're unique.

And that's -- the philosophical conclusions

of that are very deep.

But let's go with the idea, the nicer idea in my view,

that it is much more probable.

So I think we're all agreed that somehow,

a chemical mixture transforms itself into life.

So how can we make progress

on that mysterious process that we don't know?

Well, the first thing is we could ask a chemist, of course.

Seems like the obvious thing to do.

Could a chemist cook up life in the lab,

and show us how it can be done?

Well, the first attempt to do this was made

in a famous experiment by Stanley Miller,

under the guidance of Howard Urey, way back in 1952.

And what they did was to take the components

of what they thought the Earth's early atmosphere was like,

put it in a flask there, and sparked electricity

through it for a week.

And a sort of brown sludge appeared in this flask.

And when they analysed the sludge,

they found to their delight, it contained amino acids.

Now, amino acids are the building blocks of proteins.

And so you might think, "Well, that's one step on the road

to life, one small step."

And that was the pervading view in the 1950s.

Well, you know, if Miller and Urey could get amino acids

in a week, imagine if they could get funding

to run the process for a million years.

You know, maybe they --

[laughter] it would just be a road,

a pathway down which a chemical mixture would be inexorably

conveyed by the passage of time, that life is the destination,

just more of the same.

That early optimism has gone away,

probably because of thermodynamics it's very easy

to make amino acids.

In fact, you can find them in meteorites.

You don't need very special conditions.

It's because it's what we call "thermodynamically downhill".

It's favoured, whereas, the next steps of the process,

assembling the amino acids

as the peptide chains, is an uphill process.

It goes against the thermodynamic gradient.

And amino acid is only one part of the whole story.

We also need nucleic acids, and a whole bunch of other things.

And really making those things in the lab it turned

out to be really, really difficult.

But part of the problem is, of course, what we don't want

in the origin of life stories, the only thing

like an intelligent designer.

And the people who call themselves

"synthetic biologists", or in the Miller-Urey experiment,

they set out trying to design an experiment, and make life.

So even if we could do it in the lab,

even if with enough funding, we could one day make life,

that still wouldn't convince me that nature would know how

to do it without having a plan in advance

without being intelligently designed,

which I don't think it is.

So that's one problem.

The other problem is look at this picture.

Now, this is a picture of what is called

"intermediary metabolism".

These are the pathways in a modern cell,

only a small part of this.

And in the tray these things are known as "reticular grammes",

for obvious reasons, [laughter] almost approaching the

complexity of the London underground map.

[Laughter] And so biology is very complex.

And so the question is if you just account [inaudible] make

into building blocks, you know,

what about assembling all those building blocks

into something much more complex like this?

So it's a little bit like saying we've cracked the problem

of how the Empire State Building came to exist.

We've discovered how to make a brick.

[Laughter] So the rest must just be more of the same.

So it's not how to make the building blocks,

it's how to assemble them into these very specific,

very elaborate complex structures.

But it's actually a more fundamental problem running

through all of this.

It's, really, a philosophical problem.

And it's one that preoccupies me

in my own research in this field.

And that is the problem best asked, "What is life?"

And so that's something that scientists

like to do again and again.

And it makes great coffee time conversation,

goes on and on and on.

But basically, if you talk to a physicist or a chemist,

"What is life", you'll be told a story in terms of things

like matter, and force, and molecules, and energy,

and entropy, and all that sort of stuff.

And a lot of bit's been worked out.

And so that's the narrative you get.

If you go to biology department, ask a biologist, "What is life,"

you'll be told a story in terms of coding, and signals,

and instructions, and translation, and transcription,

all those sorts of things.

In other words, information speak.

So we have two complementary descriptions of what life is.

One is it's all about molecules, and shapes,

and chemical affinities.

And the other is it's all about information processing.

And you might think, "Well, how can we have chemistry

and physics, departments and biology departments

in the same university?

These people are talking conflicting languages."

And they say, "No, no, no; these are complementary descriptions

of the same phenomenon."

And that's well and good,

so long as you're discussing the phenomenon as we find it.

But the problem about life's origin is

that then we're talking about the physics

and chemistry transforming into the biology.

We're talking about matter, and force, and so on,

turning into information processing.

If you like, procrudely, we're talking about stuff turning

into bits, informational bits.

How does stuff become bits?

How -- because in physics, the stuff calls the shots.

Cause and effect are framed in terms of particles,

and forces, and interactions.

In biology, causality is framed of terms

of signals, and information.

How did matter dispel upon information,

that type of causal efficacy?

It's a very deep problem.

There's an analogy, which I think you will appreciate,

and that is we're computing.

So here's a screen shot of my computer a couple of years ago.

And this is my beautiful wife, Pauline, here.

And we see we've just been

to the Taj Mahal, all very romantic.

And then there are some other stuff less romantic there.

But, you know, to me if I just had never seen a computer

before, Windows would seem like a miracle.

Just remember Crick, seems almost a miracle.

Explain it to me.

So if I go to a computer science department and say,

"Explain Windows to me," and if the scientists took the back

of the computer and said, "Look, I can explain it.

We've got some silicon in here, and there's some copper,

and the there's some ion, and, you know,

we noticed with the silicon if you look very carefully,

there's these sorts of patterns inside.

And we're not completely sure of all the details yet,

but we think it's got something to do with those patterns.

And, you know, we're half on the trail and we will be able

to explain all of Windows very soon in terms of this."

Well, you wouldn't be very impressed,

because what you're getting here is a story

about the hardware of Windows.

And that's fine; I'm not denigrating the people

who work on computer hardware.

Where would we be without them?

But in the origin of life field, the hardware,

the chemistry corresponds to the hardware.

It's the stuff of life, the substrate

in which life's magic is instantiated.

What we're really interested in, what I'm really interested

in is the software, the software of life.

So for a hundred years,

the origin of life field has been dominated

by chemists looking for the hardware, and that's fine,

they can get on with it.

But they haven't made a lot of progress.

In recent years, we've started asking about,

"What about the software?

What about the information processing capabilities?

How do we make progress for that?"

Well, maybe you ask a computer scientist.

A famous founder of Computation, John von Neumann,

he and Alan Turing together,

responsible for the modern electronic computer.

And von Neumann was very impressed by the analogy

between what is often called a "Turing Machine",

a universal computer, a machine that could compute anything

that was computable in one machine,

a universal general purpose machine, with the notion

of a universal constructor, a system that could construct,

according to a programme, anything you asked it

to construct, including itself.

So it would be a self-replicating machine.

And von Neumann wrote papers and a book about the concept

of well asking the question, "Is it possible to build a machine

that could construct any physical system,

including itself?"

And so he laid down the logical architecture of what

such a machine would be.

And this was before the unravelling of the genetic code,

and DNA, and all that stuff.

Turns out that life as we know it is actually very much

like a von Neumann self-replicating machine.

But needless to say, we haven't made any

such machine [inaudible].

Although, some people think the 3D printing is getting rather

close to a von Neumann machine.

But basically, we don't fully understand the

software principles.

We understand a bit about the hardware,

don't understand very much about the software,

but in my personal opinion,

advances in understanding life's origin will come

from a better understanding of the complex wave

of information processing going on inside organisms,

and how that may have emerged from information processing,

and primitive chemical networks.

So that's where I think the future lies.

But mostly we haven't gotten there yet.

So this is a list of questions before I go

onto the final part of the talk.

How did it all start?

How did software emerge from hardware?

How did bits come out of stuff?

We don't know.

How did nontrivial programmable construction --

because it's not -- so living organism just doesn't make any

old thing, it makes a very, very specific thing according

to instructions contained in the DNA.

How did that type of programmable

and possibly reprogrammable --

because that's how you get evolution,

life gets reprogrammed to produce something different;

how did reprogrammable construction emerge just

from dumb molecules just banging around

and interacting with each other?

How did digital information storage emerge?

So we're all convinced of the power

of digital information processing.

And I'm old enough to remember the side rule.

That's what I called an analogue computer.

So side rules you whipped out of your pocket

and did the calculation like this.

These days, we think now that's really very inefficient.

We use digital computation, and now we have digital radio,

digital television, digital everything.

And that's because it's a very,

very efficient way of doing things.

Well, life went digital three-and-a-half billion years

ago with life.

How did it do that?

How did it go from storing information just

in like chemical gradients, to storing it

in these digital units, like nucleotides, and DNA,

and the codons, and so forth?

I won't get into it.

And then it's all very well

to have digital information processing going on,

but it's got to do something.

It's got to be useful.

If you sequence a molecule of DNA, it's just a sequence.

You can't tell my looking whether it's junk,

or whether it's something that it's going to code

for a biologically functional protein.

There's nothing in the sequence itself.

Nature is blind to such sequences.

It's only in the context of the entire milieu,

and that may have been much more

than just the micro-environmental cell,

it could mean the micro environment of the organism.

It's only in that context we can say

that we have biologically functional

or useful information.

How did that concept

of the global environment having some sort of --

I would still say causal efficacy over what's going

on in the molecular level, how did that happen?

And let me repeat the answer, we haven't a clue.

I mean, we really are in the dark.

We've got some great ideas.

And I have some colleagues doing great work investigating this

stuff, but it's at the level of toy models.

We really feel that we'd like to understand

if there is a life principle, we think it's in the field

of complex designs, and software,

and information processing,

that that's where we would discover it.

And we'd like to know if there is such a principle,

is it general across a wide range of complex systems,

or is something specific about the carbon?

Okay. So given that we're really stuck,

how can we test the hypothesis of lifestyles easily?

Is there somewhere we can just go and find out.

There is one way, it turns out, and that is we look

for a second genesis of life, life two, if you like.

If we can find that life was started more than once,

well then -- independently more than once,

well then it does look like it's pretty easy to happen.

Well, what is the most Earthlike planet that we know

where we might go to look for life two?

Would it be Mars?

Would it be an extra solar planet?

No. The most Earthlike planet we know is Earth itself.

If it's the case, as Christian Verdu thinks, that life pops

up readily in Earthlike conditions,

it's a cosmic imperative,

then surely it should have happened more

than once right here on Earth.

Well, how do we know it didn't?

How do we know all life on Earth is the same life?

Has anybody taken the trouble to look?

Well, it turns out that until my colleagues

and I raised the awareness of this issue some years ago,

nobody had really even thought about it.

But it could be, I should say that most life

on Earth is microbial life

and most microbial life hasn't been characterised,

let alone sequenced, and cultured in the lab.

So most of that life is mysterious.

How do we know it's all the same life?

You've got to delve into its biochemical innards.

You can't tell by looking whether it's the same life

as Earth, or some other type of life.

So it could be that there is truly alien life

under our noses or even in our noses.

[ Laughter ]

So if life on Earth started more than once, we're talking not

so much about another branch from the tree of life,

but another entire tree, two trees of life.

How might that have happened here on Earth?

Well, I told you about the cosmic bombardment.

So imagine that the [inaudible], say, four billion years ago,

then along came an impactor, wham, and blasted a lot

of material off, sterilised the planet,

and then things cooled down, and then life two got going.

But then a few million years later, some of that material

with life one cocooned inside it came back again.

Then you'd now have two forms of life on Earth,

life one and life two.

And this could have gone on again and again.

So the conclusion is that we sometimes cause a

shadow biosphere.

If Earth has, or once had, a shadowed biosphere,

we could conclude it does start readily.

And therefore, it would be widespread in the universe.

We could conclude that life would be a fundamental,

and therefore a significant cosmological phenomenon,

and not just a trivial low collaboration.

We wouldn't then be the freaks I've been talking about.

We would actually feel at home in the universe.

I'm going to finish by just touching on the subject

that I think fascinates everybody about life

in the universe, why we want to know the answer

to this question, and that is the question,

"Are we alone in the universe?

Is there anybody out there?"

So this is the subject of setting the search

for extraterrestrial intelligence.

And I should just mention in passing that for some years,

I've been the chair of the SETI post-detection task group.

So it's our job to deliberate on what happens if ET calls.

[Laughter] You've ask [inaudible] question time.

But at this age, of course, we don't know if there's any life

out there, let alone intelligent life.

But the way people search for it is using radio telescopes,

like this one at [inaudible] in New South Wales; very famous.

There's even a dedicated system called the

"Allen Telescope Array", which was partially paid

for by Paul Allen, but has now run out of money.

And so it's been sort of hibernated.

The plan is to have some hundreds of dishes

like this dedicated to just looking to see --

sweeping the skies to see if there's any radio signal

from ET coming our way.

But so far, only an eerie silence and no money.

So this is -- the way forward lies either

in getting more money, or we're thinking a bit outside the box

on how we might detect signatures

of intelligent life beyond Earth.

But I'd like to draw this to a conclusion by a quotation

from Frank Drake, who started the subject of SETI in 1960.

So that's 45 years ago.

And this was an incredible gamble when Frank Drake did it.

People thought he was totally crazy.

As I've explained, at that time nobody really believed there was

only life beyond Earth.

And Frank has been persistently looking for this.

And I have to admire his staying power.

Who else do you know who has designed an experiment,

run it for 45 years, got a null result,

and still remains upbeat about the future?

[Laughter] But Frank is convinced that we're going

to discover intelligent life beyond Earth very soon.

And I hope he's right.

But at this stage, we cannot give the betting odds.

But I will finish because I think he described

so well why everyone cares about the subject

of life's origin and are we alone.

They care because it touches upon what we human beings are,

and how we fit into the universe.

So Frank says that SETI is the search for ourselves,

who we are, and where we fit into the universe.

So ladies and gentlemen, thank you very much.

[ Applause ]

The Description of Paul Davies on the Origins of Life