How do new complexity and emergence theories shed light on
the origin of life?
The origin of life on Earth is one of the greatest of
mysteries, and the first thing that anybody who wants to talk about it
should say is that nobody knows how life started on Earth. It may have
gotten here on a rock from Mars; it may have come in on a space ship
from Alpha Centauri, or it may have started here on Earth, as most of us
We should also understand that any theory or experiments that we have
now that may help tell us how life started or how to create living
systems does not necessarily answer the historical question of how life
actually started. Nevertheless, again, I think that we're on the verge
of an enormous revolution.
There has been a standard view of how life started that has been extant
roughly speaking since Watson and Crick discovered the structure of DNA,
with its famous double helix. The magic of the DNA molecule or RNA, its
close cousin, is that if you specify the letters, the nucleosides coming
down one side of the helix in DNA, it's A, T, C and G, because of the
famous Watson-Crick pairing, an A on one side binds to a T on the other
side, on the other strand, and the C on one strand binds to a G on the
other strand. So as Watson and Crick famously remarked, "The structure
of the molecule and its symmetry of this kind already suggests how it
The beautiful symmetry in which the sequence of nucleotides on one
strand specifies the sequence of nucleotides on the other strand has
suggested to most workers that life must be based on
template-replicating properties. Thirty years of work have gone in to
try to prove that view.
Now I think we're coming to a new view about a possible root to the
origin of life which is to many practitioners rather startling and
unconventional. My personal biased view is that it's got a good chance
of being correct.
You see, life at its root is based on the idea of catalysis. Catalysts
speed up molecular reactions, and what a cell really is is a system
where every molecule that is in the cell has its formation catalyzed by
another molecule in the cell.
My own view is that it's relatively easy for collectively auto-catalytic
sets of molecules to emerge.
In particular Reza Ghadiri at Scripps Research Institute has made the
first protein that is able to copy itself. Now, if a protein A can
catalyze the reaction that forms A out of two fragments of A, what about
a system in which there are two proteins, A and B? A catalyzes the
formation of B out of B's fragments; B catalyzes the formation of A out
of A's fragments. So it's collectively auto-catalytic.
We're very close to doing that: Reza and his colleagues are on the verge
of succeeding. But if you can have a system with two proteins that
catalyze one another's formations, A and B, why not three or four or ten
or 100 or 1,000?
This begins to tell us that life need not necessarily be based on the
beautiful template replicating properties of DNA and RNA; it may be
based on something much more fundamental, which is polymers and
catalysis, and a kind of collective closure; auto-catalytic set achieves
a collectively closure in which every molecule gets its formation
catalyzed by some molecule such that all of the catalytic jobs get done.
It's an objective property of the set of molecules; they either are or
not collectively auto-catalytic. So I think we're going to begin to
view the emergence of life in a quite different light as the emergence
of collectively auto-catalytic sets.
Now, the next question is how hard is it to get such systems? Does it
take a careful crafting of a chemist, or can it arise by chance? The
body of theory I've been working on now for more than a decade suggests
that it's not hard.
You see this with an analogy: suppose you take 10,000 buttons and spread
them out on a hardwood floor. You have a large spool of red thread.
Now, what you do is you pick up a random pair of buttons and you tie
them together with a piece of red thread. Put them down and pick up
another random pair of buttons and tie them together with a red thread,
and you just keep doing this. Every now and then lift up a button and
see how many buttons you've lifted with your first button. A connective
cluster of buttons is called a cluster or a component. When you have
10,000 buttons and only a few threads that tie them together, most of
the times you'd pick up a button you'll pick up a single button.
As the ratio of threads to buttons increases, you're going to start to
get larger clusters, three or four buttons tied together; then larger
and larger clusters. At some point, you will have a number of
intermediate clusters, and when you add a few more threads, you'll have
linked up the intermediate-sized clusters into one giant cluster.
So that if you plot on an axis, the ratio of threads to buttons: 10,000
buttons and no threads; 10,000 buttons and 5,000 threads; and so on,
you'll get a curve that is flat, and then all of a sudden it shoots up
when you get this giant cluster. This steep curve is in fact evidence
of a phase transition.
If there were an infinite number of threads and an infinite number of
buttons and one just tuned the ratios, this would be a step function; it
would come up in a sudden jump. So it's a phase transition like ice
Now, the image you should take away from this is if you connect enough
buttons all of a sudden they all go connected. To think about the origin
of life, we have to think about the same thing.
What would be the significance of finding extra-terrestrial
Once again I think we're on the verge of a radical
transition. Biology is based on earth life not surprisingly. It's
our only exemplar. Suppose we either create life anew in a test tube
somewhere in the next few decades I happen to believe that we will
or we find it on some chunk of Mars block or hiding in some sea on one
of the moons of the giant planets. We will then have a second form of
Assume for the moment that it's radically different than earth life,
meaning not based on DNA and DNA template replication. So it's clearly
of independent origin. This is going to be of a stunning scientific and
spiritual importance to us. It's going to imply first of all we're not
alone; we're really not alone. But secondly, scientifically, once we
have a second form of life, we're going to confront the invitation, and
in fact the demand to construct a general biology. We're going to have
to understand and think about and probe the question: what would life be
like anywhere in the universe? What are bio-spheres like anywhere in
the universe? Are there general laws that characterize bio-spheres
anywhere despite the detailed filigrees of chance and bricolage in
Francois Jacob's work, the catch-as-catch-can way that evolution works
and hooks things together?
I think that we are on the verge of a general biology. It will require
a new physics, a new chemistry. In particular, we can get at the
collective behaviors of complex chemical reaction networks. New
technologies will arise from it. We will see ourselves in a very
different way in the universe. We are going to see ourselves as natural
expressions of matter, energy, organization unfolding, a terribly
different view than we've had for the past three centuries.
You've written that evolution is not a matter of chance
You know, Jacob and Monod, the two French Nobel laureates who
discovered that genes turn one another on and off, captured our standard
and still wonderful sense of evolution. Moneaux's phrase is evolution
is chance caught on the wing. Jacob's phrase was that evolution is
bricolage, the French word for jury rigging. And they're both right.
Evolution is time after time after time the emergence of utterly
unexpected, novel, unbelievably crafty ways of crafting things that
work. Nevertheless, evolution may not be merely bricolage, merely
chance caught on the wing, and Darwin's mode of evolution, natural
selection. There's another source of order in organisms and in the
biosphere. It's the process of self-organization, spontaneous order.
We're seeing it all over the place. We knew before that if you take
water and you look at the formation of a snow crystal, it has an
evanescent six-fold symmetry, and that didn't require natural selection.
What we're beginning to find in these new areas of mathematics called
complexity theory is the spontaneous order of stunning depth, power, and
intricacy which means that evolution is a marriage of natural selection
and self-organization. It's not that one is right and the other is
wrong. Both are true. And that means that we have to rethink evolution
anew, and frankly, no one, including I, knows how to do that.