h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Environments can be identified at so many levels.

The environment for a molecule is the medium in which it exists (for this discussion I'll assume a liquid medium). I have no background in organic chemistry (other than a fondly remembered girlfriend), so correct me if I'm wrong, Orcus...

There are ions (potential chemical partners), like the hydrogen and oxygen that make up the water, sodium and chlorine that might make it taste salty, and lots of others which you might not want to taste.

There are organic molecules and strings in transition between one molecule/state and another.

There are particles (a sand grain, an acid-etched sand grain, a tiny clump of soapy stearate molecules) and surfaces (rocks, stones, the boundary between liquid and air). And there are layers (more or less chemically active collections of molecules and particles and slimes and other things which hang at various levels in the water because of their density.

There are bubbles of gas generated by reactions at one level which move up (or occasionally don't) and may prompt other reactions in other chemical collections.

There's the rate of movement of the liquid medium, its temperature (levels and rates of change), the types and quantities of radiation (light, heat, cosmic rays...) to which the molecules are exposed and which might contribute energy to promote new reactions.

Then there's the disruption of the environment (waves, winds, chemical explosions, changes of temperature, volcanic surges) which might take one molecule close enough to interact with another.

It's difficult to fully wrap our heads around this subject but in asking 'How life came about?' you get the same kind of problems answering it as you get with 'How did the universe come about?'.

The universe has always existed, or has it? If not what was before? What did the Big Bang emerge from?

You can look on the universe as being an entity and I like to consider the following - Since our physical bodies are connected but separate from our minds and thoughts and each thought itself doesn't know what other thoughts are going on, why can't life as we know it be the thought processes of the universe trying to work out what is going on (a bit like the Whale over Magrathea), only in a much longer time frame (more like Deep Thought).

We don't know exactly how thoughts form but it's not a smooth process or DNA would have written his books much faster. While trying to think our subconscious minds may throw random things together and then tell us anything it thinks may be useful that comes from that.

The Universe as we call it may have thrown random things together subconsciously and some of these things have led to 'life as we know it' (By random things i'm not talking just biology and chemistry here I mean circumstances). You CAN think of absolutely anything but with nothing to focus in on it's hard to come up with any really good ideas.

[You have to understand though I'm talking about an unknowing universe doing this, if you think 'I want to catch a ball' that's all you consciously know about what your mind does to achieve it.]


I appear myself to have shifted the problem to that of the Universe rather than solve it but having just read a thread called is there life after death I feel some good advice is to not spend too long trying to answer the important questions life has to offer or you might just waste it.

Think of life as a limited offer, while stocks last and go make the most of it.

A good thread to find/start would be - 'Ways to get a lot of enjoyment out of life without stopping anyone else enjoying it'

I think i'll go and start it myself actually. I can't link it yet obviously so do a search or I may post a link in a reply to this thread.

Albatross.

I just found this - [URL removed by moderator]

On there it seems to sum up a bit more what I was getting at.

To quote 'aramis' at MIT...

On November 2nd, 2000, Douglas Adams visited Massachusetts Institute of Technology, where he gave a talk about the book he co-authored with Mark Carwardine, entitled "Last Chance To See". Alas, for members of the audience, it was also the last chance to see the witty and ingenious man who stood behind the books we respected and loved.

On that day, Mr. Adams concluded his talk with a brilliant metaphor. He compared a human being to a puddle that wakes up one morning, looks around and says, "What a nice hole in the ground - it's made just for me ! Look at how nicely it's indentations fit my beautiful curves, and the depth and the radius are just right...". And as the puddle carried on in its self-centered pleasure, the sun kept shining on it until there was not a trace of it left. Then, Mr. Adams asked us to remember the story and never reduce ourselves to the level of that puddle, for that will give us many more "chances to see".

There - From the man himself. Don't be a puddle!

Albatross

Albatross, we're talking about the subject of how life got started here, in this thread, because it interests us. We can also talk about anything we like, on hundreds of other threads. But here, we're talking about how life got started. Hope you don't mind. You're very welcome to join in.

Orcus, would extreme cold or heat - I mean the kind of temperatures that you'd find in the coldest parts of space or the hottest parts of sun - allow the sorts of self-arrangement of matter that could be the very start of the process that leads to life? I'm just wondering what the limits are. I've read that some people think that life started where conditions were extreme - deep inside rocks or near volcanic vents on the sea bed. That makes some sense if life started 3 - 4 billion years ago when earth was a very hostile environment just about everywhere.

'How' life started is what I'm really interested in but even so, if you know the limits of the conditions in which the right sort of chemicals could get together initially, it can narrow down where it started. And that might give a better idea of how it started.

Liquid does seems the most favourable starting point, partly because it's hard to imagine life without water. I can easily visualise the scene you describe Mund. As described, it looks as though it shouldn't be too difficult to recreate in a lab. Perhaps when life began, at a time when the planet was busily making itself (more than it is now), a condition occurred that can't be reproduced in a lab ... or simply hasn't been thought of yet, like 2 completely different environmental conditions being suddenly and violently thrown together. Perhaps the very first combining of chemicals that were the precursors of life came together in completely different (cold, hot, dry) conditions and were thrown into a liquid environment where another set of conditions made it possible for the water to be 'seeded' somehow. Your description is very persuasive.

That life is the thoughts of the universe doesn´t seem right. Besides being a theory that you can pretty much not prove or disprove, it also seems a bit like circular logic. Giving the universe thoughts that create life, when thoughts only happens in life. Doesn´t seem right. And what you described does seem to be pretty much what people talk about when they describe the probabilities of life. With throwing a lot of things together and it ends up as life eventually.

But on the other hand, some say consciousness(whatever it is) is simply an inevitable result of complexity. If that is so, maybe the most complex thing we have, the universe, is also conscious. That would be something a bit like God. And it might have the same illusion of free will as we have. This is of course just metaphysical crap, but an interesting thought.

As for the puddle, didn´t DNA use that to talk about the theory of anthropo-something. The idea that because the universe seem perfect for humans we must have been the purpose of it.

You're referring to the anthropic principle, subject of lots of books and things a few years ago. The universe must have organised itself to produce us because - look! - here we are. Ants seem to do rather well, so god has six legs. Bacteria outnumber all other life forms put together, by numbers and weight. So that's what the universe is for.

I think not.

A friend of mine argued that, if Planck's constant was 4.83, then buses would diffract between telegraph poles. It made just as much sense.

ANYWAY!!! BACK TO THE BEGINNING OF LIFE...

We can imagine a particular set of chemical precursors which might have produced some primitive form of life when stirred in the right temperature and subjected to the right temperatures and struck repeatedly by lightning. And we can set up an experimental environment and hope to have the miracle of life produced for us.

But that would be a small volume of material, a small number of candidate molecules out of the complex and geographically varied mix which we can only guess at. And we wouldn't wait for thousands of years for results.

It's amazing that any complex reactions have been observed.

Is it possible to make an estimate of the chances of life starting under a given set of circumstances? I don't know much about biology and like most people, I imagine, until I started thinking about it, I sort of assumed it was just a matter of some goo getting animated. That vague. How complicated is a protein? How complicated is the bit of DNA or RNA that makes the simplest protein? If there are (I don't know what a realistic number might be) say a dozen different amino acids or so and they cluster together in any old order, is that a protein? Do they have to be in any particular order to be a protein? If they have to be in a particular order to be a protein, how can they repeatedly come together in the right combination and shuffle themselves into the right order?

Oh dear. Sorry about all the questions.

Hi again, I was merely talking about chemicals having patterns of behaviour Sal, not really life. If life is only really possible with carbon based molecules (which is probable as it is really the only element that can combine with itself and others in such complexity - silicon has nowhere near the potential of carbon in this respect) then the limits are the temperatures and pressures at which these molecules are stable. Above around 100 degrees C, you will seriously denature proteins and nucleic acids if not start to decompose them (denaturing is a protien unfolding - they have a specific fold which is their active conformation - if this is destroyed it is still the same molecule but will not do anything anymore). Go higher in temperature then the molecule will start to react with oxygen and other compounds and simply decompose - basically they will burn. Carbon based polymers are not very stable at all above such temperatures. As far as cold goes, you can probably go very low if the pressure is high enough to prevent water freezing as ice crystals will destroy the delicate cell architecture. The cold will just slow things down which isn't necessarily deleterious.

Do you know any statistics Shorn Canary? There are 20 naturally occurring amino acids that make up our proteins. The smallest proteins of all are probably around 50 or so amino acids long so to get the right permutation the chances are astronomically small. Proteins normally contain hundreds of amino acids in a specific order and in a specific folding pattern.
DNA is a totally different type of molecule, it is a polymer (repeating chain of unit molecules) of molecules called nucleotides. These are comprised of a phosphate-sugar-base linkage, the bases used in DNA are Guanidine, Adenine, Cytosine and Thymidine (the G A C T abbreviations you see for DNA sequences).

This is the essential problem, DNA encodes for proteins (three base units, say CCG are codons that code for a specific amino acid). The code on the DNA means that the new protein will always be the same as the previous one. DNA itself cannot do chemical reactions so it requires a complex system of already existent proteins to perform the necessary chemical reactions to copy the DNA code into a protein.

So which came first? DNA - unable to replicate itself as it cannot perform the chemical reactions required. Or proteins, which do the chemistry but have no code to make another protein? This is the chicken and egg problem of how life began.

Proteins and DNA are fantastically complicated.

A typical protein is say 200 amino acids long and contains varying amounts of most, if not all of the 20 natural amino acids. Proteins, when they act as enzymes (the proteins that do all the chemistry) must have a very specific shape. Just think about a pearl necklace 200 pearls long. How many different ways can you arrange into different loops and clumps? It is even more complex than the necklace however as amino acids are not spheres like pearls, they have shape, some are big, some are small... In short, a 200 amino acid long protein has trillions of possible ways of arranging itself -only 1 of which will do the job it is needed for.

Care to do the estimate yourself now?

Questions are cool BTW - hope that helped a bit

That's a hell of a challenge for a bird brain, Orcus. Is it something like 200 to the power of 200? If so, that's absolutely blooming astronomical. That's too big a number for me to type. It would take too long and wear out my zero key. AND the problem is a lot more puzzling than the chicken and egg thing because there was life before chickens. Some ancestor of the chicken invented the egg so the egg came before the chicken.

Well that's it then. I don't really exist, do I?

You can see why so many people cast about for supernatural explanations, can't you? Trouble with that is, if the chances of "simple" (my foot) things like proteins forming by accident are so slim, how much more slim the chance of a fully functional supernatural being popping into existence.

Thank you. Your answer helped ..... to increase my wonder by a factor fansands. This is very vexing. Is there anything else you're not telling me that would make it all make sense?

The idea that life self-assembled from a primordial soup of ingredients via some fantastic fluke is not the only plausible explanation. There are lots of problems with this idea. First, we don't actually know what the initial ingredients were. Sure, the existing chemistry places some constraints on the starting chemistry, but adaptation over billions of years leaves few clues. Using the house analogy, you can look at the building blocks of a skyscraper and infer the general properties of building materials but still be no wiser about the wood and mud used in huts to start the whole process off. The skyscraper blocks are also wholly unsuitable to build a hut - simulating the production of blocks making up advanced life may be a red herring. We can say that it must have been carbon based, and that at some point it acquired the capability to process information, possibly with RNA.

Second, the question of how life started is also a question of what is life. Life is more a process than a collection of chemicals - you could say the specicfic chemicals are incidental within certain limits. Organic chemistry nows seems to be quite widespread all over the universe - even in interstellar dust clouds, and in comets. So the presence of the organic chemistry in itself is not surprising, and doesn't necessarily mean life will subsequently emerge. Its the process thats interesting. Here i'd agree with the anthropic principle - all the fortuitous circumstances of Earth are unsuprising given that we're here to witness them. The tricky bit's figuring out which are important for life and which are just coincidence. The life-process then, is remarkably good at dissipating energy to the outside world (thus increasing the entropy of the entire universe) because it is in itself so well ordered. A nice paradox, i think. So the heat we produce is the ultimate reason for us being able to exist. Natural heat dissipating processes on the early Earth may then be a good place to look. A suggestion has been hydrothermal vents, which would have been widespread on the hot early Earth. A more and more efficient way of dissipating a heat gradient would be initially favoured by thermodynamics, then once sufficiently advanced could move on to other energy gradients like sunlight, and then eventually other living things mmm. Of course this places membranes at the centre of things, rather than as a footnote, because to maintain a gradient you have to have a boundary. So that'll have to be explained. Ever wondered why you need your daily minerals?? Perhaps its because life grew up on an iron sulphate diet at vents - the same minerals have been retained as a relic in energy-transduction enzymes in most lifeforms.

Of course all this means that life may be a natural stage in the evolution of a planet under the right conditions, and maybe more widespread than anticipated. Of course its anybody's guess exactly what the 'right conditions' are and why life has perservered on Earth for so long. Did Venus develop in the same way before the Sun heated up? Has it started at Europa but not got beyond the hydrothermal stage? The problem is we have only one example - Earth. Earth 'life' may be just one variant of huge range, depending on the conditions of the home planet. Or maybe it is an experiment to find out how life started and is being 'video-taped' as we speak?! An explanation for the ice ages you think - seeing how we cope are they?! ok i'm going to stop right there!

ahhh good to get all that out

I'll answer your other points when I've had a good think, but life on earth a video-taped experiment...? Didn't somebody we know write a book about that once?

hmmm ... yes i remember, but not as a computer rather an organic chemistry experiment. of course there's the panspermia idea aswell, whch was supported by some research recently that showed bacteria could be 'frozen' then reaminated (memories of austin powers ) after long periods of time. i guess you can never know for sure - its just a question of which idea is the most plausible ...

We'd probably assume a carbon-based system from the earliest times, but we can't assume that any of the molecules we know now would have been in at the beginning.

RNA might have been an early stage of development of what we would recognise as a life system, but there may have been many stages on the way to it, which have disappeared by now.

One of the interesting things about complex molecules is that they adopt shapes. The shapes of crystals can be expressed in relatively simple geometric terms, and as more and more of the relevant substance drops from the liquid to the solid form it takes up the same structure.

Long organic molecules curl themselves into shapes that have more in common with knots. One interesting point about some of them is that there are "sites" along the molecule which can form links with other atoms or other molecules.

And then some of them can change their shape according to their environment - if the temperature changes, or if another chemical is present. Which means that molecule A might link up with various atoms in one state, then release them as a new molecule B after an environmental change.

There are lots of missing links in the evolution of the chemical precursors of life. But once you have a molecule which is capable of picking up material from the environment, then dropping it in a new form if something else changes, you have an information transfer, so you have something over and above the simple molecular level.

(Again, please advise on any mistakes or misunderstandings due to my lack of formal biochemistry etc.)