Finding life we cant imagine Christoph Adami
so I have a strange career I know it
because people come up to me like
colleagues and say Chris give a strange
career and I can see that point because
you know I started my career as a
theoretical nuclear physicist and I was
thinking about quarks and gluons and
heavy ion collisions and I was only 14
years old no no no no I wasn’t 14 years
old but after that I actually had my own
lab in a computational neuroscience
department and I wasn’t doing any
neuroscience later I would work on
evolutionary genetics and work on
systems biology but I’m gonna tell you
about something else today I’m gonna
tell you about how I learned something
about life and I was actually a rocket
scientist I was a rocket something I
wasn’t really a rocket scientist but I
was working at the Jet Propulsion
Laboratory in sunny California where
it’s warm whereas now I’m in the Midwest
and it’s cold but it was an exciting
experience one day a NASA manager comes
into my office sits down and says can
you please tell us how do we look for
life outside earth and that came as a
surprise to me because I was actually
hired to work on quantum computation yet
I had a very good answer I said I have
no idea and he told me bio signatures we
need to look for a bio signature and I
said what is that and he said it’s any
measurable phenomenon that allows us to
indicate the presence of life and I said
really because it’s not easy I mean way
of life can’t you apply like a
definition like for example a Supreme
Court like a definition of life and then
thought about it a little bit and I said
well is it really that easy because yes
if you see something like this then all
right fine
I’m gonna call it a life no doubt about
it but here’s something it goes like
right that’s life - I know that extent
if you think that life is also defined
by things that die you’re not in luck
with this thing because that’s actually
very strange organism it grows up into
its adult stage like that and then goes
through like a Benjamin Button phase
initially goes backwards and backwards
until it’s like a little embryo again
and then actually grows back up and back
down and back up sort of yo-yo and it
never dies so it’s actually life but
it’s actually not as we thought life
would be and then you see something like
that and it was like my god what kind of
a life-form is that anyone know it’s
actually not life it’s a crystal so once
you start looking and looking at smaller
and smaller things so this particular
person wrote a whole article and said
hey these are bacteria except if you
look a little bit closer you see in fact
that this thing is way too small to be
anything like that so he was convinced
but in fact most people aren’t and then
of course NASA also had a big
announcement in fact President Clinton
gave a press conference about this
amazing discovery of life in a Martian
meteorite except that nowadays it’s
heavily disputed if you take the lessons
of all these pictures then you realize
well actually maybe it’s not that easy
maybe I do need a definition of life in
order to make that kind of distinction
so can life be defined well how would
you do about it well of course you go to
breathe you know Encyclopedia Britannica
and open that L know of course you don’t
do that you put it somewhere in Google
and then you might get something and
what you might get and you go there
anything that actually refers to you
know things that we are used to you
throw away and then you can might come
up with something like this and it says
something complicated with lots and lots
of concepts who on earth would write
something as convoluted and complex and
inane it’s actually you know a really
really important set of concepts so I’m
highlighting just a few words and saying
definitions like that rely on things
that are not based on amino acids or
leaves
or anything that we are used to but in
fact on processes only and if you take a
look at that this was actually in a book
that I wrote that this was artificial
life and that explains why that NASA
manager was actually in my office to
begin with because the idea was that
with concepts like that maybe we can
actually manufacture a form of life and
so if you go and ask yourself what on
earth is artificial life let me give you
like a whirlwind to of how all this
stuff came about and it started out
quite a while ago when someone wrote one
of the first successful computer viruses
and for those of you who aren’t old
enough you have no idea how this
infection was working namely through
these floppy disks but the interesting
thing about these computer virus
infections was that if you look at the
rate at which these infection work they
show like the spiky behavior that you’re
used to like from flu virus and it is in
fact due to this arms race between
hackers and operating system designers
that things go back and forth and the
results is kind of a tree of life of
these viruses a phylogeny that looks
very much like the type of life that
we’re used to at least on the viral
level so is that life not as far as I’m
concerned why because these things don’t
evolve by themselves in fact they have
hackers writing them but the idea was
taken very quickly a little bit further
when a scientist working at the Santa Fe
Institute decided why don’t we try to
package these little viruses in
artificial worlds inside of the computer
and let them evolve and this was stay in
rasmussen and he designed the system but
it didn’t really work because these
viruses were constantly destroying each
other but there was another scientist
they had been watching this an ecologist
and he went home and said I know how to
fix this and he wrote the chera system
and in my book is in fact one of the
first truly artificial living systems
except for the fact that these programs
didn’t really grow in complexity so
having seen this work worked a little
bit on us this is where I came in and I
decided to create a system that has all
the properties that are necessary to see
in fact the evolution of complexity more
and more complex programs constantly
evolving and of course since I really
don’t know how to write code I’ll help
him decide two undergraduate students at
California Institute of Technology that
worked with me that’s Charles or free on
the left titus brown on the right they
are now actually respectable professors
at Michigan State University but I can
assure you back in the days you know we
were not a respectable team and I’m
really happy that no photo survives of
the three of us anywhere close together
but what is the system like well I can’t
really go into the details but what you
see here is some of the entrails but
what I want you to focus on is this type
of population structures about ten
thousand programs sitting here and all
different strains are colored in
different colors and as you see here
there are groups that are growing on top
of each other because they’re spreading
anytime there’s a program that’s better
that’s surviving in this world due to
whatever mutation that is acquired it’s
going to spread over the others and
drive the others to extinction so I’m
going to show you a movie where you’re
gonna see that kind of dynamics and this
movie star I mean these kind of
experiments are started with programs
that we you wrote ourselves we write our
own self replicator are now very proud
of ourselves and we put them in and what
you see immediately is that there are
waves and waves of innovation by the way
this is highly accelerated so it’s like
a thousand generations a second but the
system goes like what kind of a dumb
piece of code was this this can be
approved upon in so many ways so quickly
so you see waves of new types taking
over the other types and this type of
activity goes on for quite a while until
the main easy things have been acquired
by these programs and then you see sort
of like a stasis coming on where the
system essentially ways for a new type
of innovation like this one which is
going to spread over all the innovations
that were before and is erasing the
genes that it had before until a new
type of higher level of complexity has
been achieved and this process goes on
and on and on so what we see here is a
system that lives in very much the way
that we’re used to life goes but what
the NASA people had asked me really was
do these guys
have a bio signature can we measure this
type of life because if we can may we
have a chance of actually discovering
life somewhere else without being biased
by things like amino acids so I said
well perhaps we should construct a bio
signature based on life as a universal
process in fact it should perhaps make
use of the concepts that I developed
just in order to sort of capture what
this simple living system might be and
the thing I came up with I have to first
give you sort of a introduction about
the idea and maybe that would be a
meaning detector rather than a life
detector
and the way we would do that it’s like
okay I would like to find out how I can
distinguish text that was written by a
million monkeys as opposed to texts that
are in our books I don’t like to do it
in such a way that I don’t actually have
to be able to read the language because
you know I’m sure I won’t be able to as
long as I know that there’s some sort of
alphabet so here would be a frequency
plot of how often you find each of the
26 letters of the alphabet in a text
written by random monkeys and obviously
each of these letters comes off about
roughly equally frequent but if you now
look at the same distribution in English
text it looks like that and I’m telling
you this is very robust across English
text and if I look at French text it
looks a little bit different or Italian
or German they all have their own type
of frequency distribution but it’s
robust it doesn’t matter what it writes
about politics or about science it
doesn’t matter whether it’s a a poem or
whether it is in a mathematical text
it’s a robust signature and it’s very
stable as long as our books are written
in English because people are rewriting
them and recopying them it’s going to be
there so that inspired me to think about
well what if I try to use this idea in
order not to detect random text from
text with meaning but rather detect the
fact that there is meaning in the
biomolecules that make up life but first
I have to ask what are these building
blocks like the alphabet elements that I
showed you well
that we have many different alternatives
for such a set of building blocks we
could use amino acids we could use
nucleic acid covered silica acid fatty
acids and for chemistry is extremely
rich and our body uses a lot of them so
that we actually to test this idea first
take took a look at amino acids and some
other carboxylic acids and here’s the
result here is in fact what you get if
you for example look at the distribution
of amino acids on a comet or in
interstellar space or in fact in a
laboratory where you made very sure that
in your primordial soup that there is no
living stuff in there what you find is
the mostly lysine and then alanine and
that’s a trace element of the other ones
okay that is also very robust what you
find in systems like Earth where there
are amino acids but there is no life but
suppose you take a you know some dirt
and dig through it and then put it into
these spectrometers because there’s
bacteria all over the place or you take
water anywhere on earth because it’s
teeming with life and you make the same
analysis this spectrum looks completely
different of course there’s still
glycine and alanine but in fact there
are these heavy elements this heavy
amino acids that are being produced
because they are valuable to the
organism and some other ones that are
not used in the set of twenty there will
not appear at all at any type of
concentrations so this also turns out to
be extremely robust it doesn’t matter
what kind of sediment you’re using to
grind up with its bacteria or any other
you know plants or animals anywhere
there’s a life you’re going to have this
distribution as opposed to that
distribution and it is detectable not
just in the amino acids now you could
ask well what about these variants
they’re variants being the denizens of
this computer world where they are
perfectly happy replicating and growing
in complexity so this is the
distribution that you get if in fact
there is no life
they have about twenty eight of these
instructions and if you have a system
where they’re being replaced one by the
other it’s like the monkeys riding on a
typewriter each of these instructions
appears was roughly the equal frequency
but if you now take us take a set of
replicating guys like in the video that
you saw it looks like this so are there
some instructions that are extremely
valuable to these organisms and their
frequency is going to be high and
there’s actually some instructions that
Yuri only want to use once if ever so
they write either poisonous or really
you know should be used at less of a
level than random and in this case the
frequency is lower and so now we can see
is that really a robust signature I can
tell you indeed it is because this type
of spectrum just like what you’ve seen
in box and just like what you’ve seen in
many ways it’s it doesn’t really matter
how you change the environment it’s very
robust it’s going to reflect the
environment so I’m going to show you now
a little experiment that we did and I
have to explain to you the top of this
graph shows you that frequency
distribution that I talked about okay
here in fact that’s the lifeless
environment where each instruction
occurs at an equal frequency and below
there I show in fact the mutation rate
in the environment and I’m starting this
Anna mutation rate that is so high that
even if you would drop a replicating
program that would otherwise happily
grow up to fill the entire world if you
drop it in it gets mutated less
immediately okay so there is no life
possible at that type of mutation rate
but then I slowly turn down the heat so
to speak and then there is this
viability threshold where now it would
be possible for a replicator to actually
live and indeed we’re going to be
dropping these guys into that soup all
the time
so let’s see how what that looks like so
first nothing nothing nothing too hot
too hot now the viability threshold is
reached and the frequency distribution
has dramatically changed and in fact
stabilized so now I what I did there is
I just I was being nasty I just turned
up the heat again again and of course it
reaches the viability threshold and I’m
just showing this to again because it’s
so nice you hit the viability threshold
the distribution changes to alive
then once you hit the threshold where
the mutation rate is so high that you
cannot sell for produce you cannot copy
the information forward to your
offspring without making so many
mistakes that your ability to replicate
vanishes and then that signature is lost
what do we learn from that well I think
we learn a number of things from that
one of them is if we are able to think
about life in abstract terms and we’re
not talking about things like plants and
we are talking about amino acids and
we’re not talking about bacteria but we
think in terms of processes then we can
start to think about life not as
something that is so special to earth
but that in fact could exist anywhere
because it really only has to do with
these concepts of information of storing
information within physical substrates
anything bits nucleic acids anything
that’s an alphabet and make sure that
there’s some process so that this
information can be stored for much
longer than you would expect the time
scales for the deterioration you know of
information and if you couldn’t do that
then you have life so the first thing
that we learn is that it is possible to
define life in terms of processes alone
without referring at all to the type of
things that you know we hold dear as far
as the type of life on Earth is and that
in a sense removes us again like all of
our scientific discoveries or many of
them it leads to a continuous death
rolling of man of like how I think we’re
special because we are live well we can
make life we can make life in the
computer granted it’s limited but we
have learned what it takes in order to
actually construct it and once we have
that then it is not such a difficult
task anymore to say if we understand the
fundamental processes that do not refer
to any particular substrate then we can
go out and try other worlds figure out
what kind of chemical alphabets might
there be figure enough about
the normal chemistry the geochemistry of
the planet so that we know what this
distribution would look like in the
absence of life and then look like two
large deviations from this this thing
sticking out which says this chemical
really shouldn’t be there now we don’t
know that there is life then but we
could say well at least I’m gonna have
to take a look very precisely at this
chemical and see well you know where it
comes from
and that might be our chance of actually
discovering life when we cannot visibly
see it and so that’s really the only
take-home message that I have for you
life can be less mysterious that we make
it out to be when we try to think about
how it would be on other planets and if
we remove the mystery of life then I
think it is a little bit easier for us
to think about how we live and how
perhaps we’re not as special as we
always think we are and I’m gonna leave
you with that and thank you very much