Consider the following: Put a handfull of distinguished scientists from different fields together, let them talk about a topic in which they share a fundamental interest, and record the session. What outcome would you expect?

Such an experiment was run last August by the people at www.edge.org under the theme "Life: What a concept!", with the participation of Freeman Dyson, J. Craig Venter, George Church, Robert Shapiro, Dimitar Sasselov and Seth Lloyd.

The transcripts of the session have recently been put on the web at
http://www.edge.org/documents/life/Life.pdf , which I read while commuting to and from the lab this week. I found it very stimulating to follow these guys venture around many scales in space and time, and I recommend that experience to you.

Assuming that most of you will think to have good reasons to shy away from reading the 168-page pdf or watching the corresponding videos (http://www.edge.org/documents/life/life_index.html), I have compiled a list of quotes from the transcript which is about 98% shorter. The order of the quotes as presented here is not chronological but should be logical to the extent permitted by the downsampling.

It is perhaps noteworthy that some of the experiments described in here were published yesterday (http://www.sciencemag.org/cgi/content/abstract/1151721).

--------
Life: What a concept!
--------
SHAPIRO :
The idea is that this is inherent in the laws of chemistry and physics. One doesn't need a freak set of perhaps a hundred consecutive reactions that will be needed to make an RNA, and life becomes a probable thing that can be generated through the action of the laws of chemistry and physics, provided certain conditions are met. You must have the energy. It's good to have some container or compartment, because if your products just diffuse away from each other and get lost and cease to react with one another you'll eventually extinguish the cycle. You need a compartment, you need a source of energy, you need to couple the energy to the chemistry involved, and you need a sufficiently rich chemistry to allow for this network of pathways to establish itself. Having been given this, you can then start to get evolution.

---
LLOYD:
if I produce chemical A, and chemical B, I put them together, then that produces chemical C in abundance. Or if chemical A and chemical B are there and chemical D is also there, then chemical C is not produced.

Now you can see the relationship of these kinds of reactions to logic, right — if A and B, then C — if A and B and D, then not C. I'm simplifying chemistry, of course, because there there are temporal dynamics as well. But those dynamics' ifthen statements, the digital statements that lie at the bottom of computation, are an intrinsic part of chemistry.

---
SHAPIRO: They have decided that one of the eight dimensions of string theory — one of the alternative universes that are now postulated by the anthropic people, are much more habitable than this. Life has a difficult job getting started. I admit this is one extreme view of life, but it's one that makes life, as Stuart Kauffman put it, something that the universe has in a sense expected, and what one does with that fact, I leave to you.

I'm not a theologian, I'm an agnostic, which says that I really do not know what's going on. But that at least in the origin of life we have a problem that can be solved not too difficultly in a laboratory, by getting the right set of molecules, by getting an appropriate source of energy — okay, we cheat a little bit, we use a beaker as the container rather than some membrane, which is perhaps more difficult to achieve than is commonly understood, and we just try to see what happens.

---
SHAPIRO:
At one point I went and spoke to the now, unfortunately, late Stanley Miller, and asked him about the circumstances of his famous Miller-Urey experiment — the one with the electric lightning and amino acids were formed — and he handed me a biographical piece he himself had written to something called the Transactions of the Copernican Society or something like that, and he described how in building his apparatus he was concerned with questions of safety, because if you take a flask and you mix it with methane and hydrogen and ammonia, the most likely result is BOOM, with flying glass in all directions, which is definitely not publishable.

[...]
On the other hand, if you believe that life could start with good molecules, given enough energy, then the universe may be rich with start-ups, and then there may be some series of levels that you have to go through, higher and higher, in order to get life more and more advanced.

---
LLOYD:
There's a digital nature to the universe, and quantum mechanics makes this happen.

---
SHAPIRO:
Entropy is like a business. It doesn't matter if one subsidiary of the business loses money as long as the others show enough profit to offset it. What you need is a larger system, the environment, and part of it absorbs energy and gets organized, and in payment for that, the rest of the environment gets disorganized, usually by going up a little bit in temperature, which is the common denominator of entropy. If you convert other kinds of energy to heat, you can pay for a lot of organization.

---
LLOYD:
So why does complex behavior arise? Well, the universe is computing at its most microscopic scales. Two electrons, two bits of information, every time they collide, those bits flip. It's just these natural interaction and information processing that we use when we build quantum computers. Now I claim — and I can claim this because this is a mathematical theorem, which is different from just mere observational evidence — that when you have something that is computing and you program it at random, just tossing IN little random bits of programming, that it necessarily generates complex behavior.

---
SHAPIRO:
[planets similar to] Earth are subject to a sort of tension because the inside, which is pure iron, is very electron-rich, while the outside, due to continual escape of hydrogen into space because water gets broken up by radiation, is electron-poor, so that at various places on the Earth there will be interfaces where electron-rich molecules are interfaced with electron-poor molecules. These are then prominent sites for the origin of life. Everyone can have his own favorite site. Some argue for the interiors of volcanoes, some argue for vents, some argue for the monolayer of the space of the ocean.

---
SASSELOV:
It turns out that plate tectonics, as understood from Earth, is a process which has been going on theoretically much more easily on a slightly bigger planet. In fact if you do the theory, as best as you can today, the Earth is at the margin of what is viable in terms of plate tectonics. Probably some of you may know that plate tectonics is a very important aspect of the viability of a planet in terms of surface conditions, because it's a good thermostat, it keeps the climate more or less stable over long periods of time, and also allows you to have easy access to the large reservoir of chemicals and gasses in the mantle of the planet.

---
DYSON: "One of the laws of physics which is absolutely crucial [...] is the fact that objects bound together by gravity have negative specific heat."

---
VENTER: What role does gravity play in the larger — in the super Earths?

SASSELOV: It's actually a positive role. In the sense that if you take the general amount of out-gassing, fluxes, which interchange between the mantle and the atmosphere of the Earth, the Earth's gravity is very close to marginal [...] in retaining a sufficient atmosphere, and hence making this thermostat being viable, and really providing you with stable conditions over at least a billion years. So having more gravity is actually better.

---
SASSELOV (on planetary preconditions for life):
"stability over long periods of time, but sufficiently low or moderate temperatures. (Stars are very stable over billions of years, but they all have very high temperatures, all throughout.) And basically the overall thermodynamic window that Morowitz is talking about, which allows complex chemistry. That's actually much broader than simply having water."

---
SASSELOV:
Then the question is, how much do we know about planetary systems? Up until 12 years ago, essentially we knew only of one: the solar system. That situation is very similar to what we have with life. We only have one example. And that's bad from many points of view, and we — 'we' meaning astronomers — learned it the hard way, because it turned out that what we had theorized about planets was very solar system-centric, and we missed a lot of things that we should not have missed, but that always happens when you have only one example of something.

---
SHAPIRO: Which is the closest known super Earth?

SASSELOV: The closest known is called — in fact there are two of them: Gliese 581c and d, and both of them are super Earths, and are just 20 light years away. Wilhelm Gliese was a German astronomer (1915-1993).

CHURCH: When will they arrive here?

SASSELOV: Next week.

---
SHAPIRO: There was a wonderful paper written by Chris Chyba and Carol Cleland about three years ago about definitions of life, and how even defining what definition is can get you into philosophical doo-doo. And it's best to look for phenomena that by their properties we would be happy to classify as alive, and to not worry too much about definition.

---
VENTER: So two base pair change in a genome could be sufficient to create a new species out of 1.5 billion.

DYSON: Yes.

VENTER: I'm not sure everybody will buy that definition... So that makes you a very different species than George.

DYSON: The real problem is the lawyers. You have the endangered species act; that means you have to make a legal definition of the species.

CHURCH: That's true. We're all endangered.

---
VENTER:
We just started asking very simple questions for example — if one species needed 1,800 genes and the other needed 550, are there species that can get by with less? Can you define a minimal genetic operating system for life? Could we define life at a genetic level? Obviously extremely naive questions but the view of biochemistry and genomics by the scientific community was very limited as well. For example when we published the
Haemophilus influenzae genome a well known biochemist at Stanford University said we obviously assembled it wrong because it didn't have a complete TCA cycle. And everybody knew that every organism had a complete glycolytic pathway and a complete TCA cycle. And Haemophilus only has half of one.

SHAPIRO: Therefore it's not an organism.

VENTER: No, therefore they assumed we made a mistake in the sequencing and the assembly. Now we see every repertoire under the sun, for example the third organism that we sequenced was the first Achaea that we did with Carl Woese, it was methanococcus jannaschii, which has neither a TCA cycle nor glycolysis. It makes all its cellular energy by methanogenesis, going from CO2 to methane, using hydrogen as its energy source. CO2 is its carbon source for all the carbon in the cell.

---
SHAPIRO:
biologists [...] only would recognize as life something that could be cultured by them and
then published. Albert Sangiorgi once said that a drug is something that, injected into an animal, produces a paper. A microorganism is something which when put in one of its favorite culture media leads to a paper. Nowadays you might say it leads to a DNA sequence, which would be a different argument.

VENTER: But eventually a paper.

---
SHAPIRO :
I was publishing papers like this and I got the reputation, or the nickname in the laboratory of the prebiotic chemist, of 'Dr. No'. If someone wanted a paper murdered, send it to me as a referee. And so on. At some point, someone said, Shapiro, you've got to be positive somewhere. So how did life start?