Where does life originate from?

[relativityfan]

hi,

can we say that life comes essentially from DNA and the resulting proteins?, but it can nly be developed in the right environemental conditions?
thank you for your reply

 

[Borek]

Your question is so ambiguous it is difficult to answer, please elaborate on what you really mean.

 

[relativityfan]

well, i just wonder if there is a merely chemical process leading to life, or if it is yet unknown by science. does science understand well now what chemical or biochemical processes lead to life and why? because cells are still very different than molecules. Can we say that cells are just a logical combination of molecules that is fully understood, is it merely a chemical process or is there a mechanism that is missing by science?

i woud be very grateful for any reply!

 

[Borek]

There is no doubt that whatever happens in the cell is just a chemistry, but we are still far from knowing all details.

However, it is still not clear to me whether you ask about origin of life, or about the processes responsible for cell building and replication. In both cases the answer is the same - chemistry with blurry details

 

[relativityfan]

ok, but this still seems very mysterious for me. i wonder if there is no major component, from chemistry, that is missing? do you also believe that known chemistry(its known trends in structures and chemical reactions) is responsible of everything in biology?

 

[Phrak]

relativityfan. I think you should stop looking for mysterious components, and instead contemplate upon the magnitude of numbers with large exponents. In a few billions of years, among trillions upon trillions of organic molecules, what might ensue.

 

[relativityfan]

OK, so what is the source of life. is it RNA, DNA?

 

[bobze]

OK, so what is the source of life. is it RNA, DNA?

I think what Borek was getting at RF, was "source" is ambiguous. Can you define what you mean?

 

[Borek]

Define "source of life".

Edit: that what happens when you uplink gets slow, bobze posted while I was waiting for refresh.

 

[bobze]

Define "source of life".

Edit: that what happens when you uplink gets slow, bobze posted while I was waiting for refresh.

 

[relativityfan]

I mean by source the most basic molecule or structure that makes a difference between chemistry and biology

 

[Borek]

That's quite unusual use of the word "source".

No such thing.

No single molecule can be treated as alive. Perhaps the closest to the simplest possible structures that can be treated as alive are some small viruses, but in a way they are not alive on their own, they need to infect a living cell to replicate, as they rely on external (cellular) biochemistry to build own copies.

Problem is, border between life and non-life is blurry, there is a whole spectrum of objects between those clearly alive (like human) and those clearly inanimate (as a rock). Depending on how you define life, border moves, and things that are alive according to one definition, can be inanimate according to other definition.

 

[granpa]

to be alive something must be able to reproduce and also able to evolve.
look up rna world hypothesis

 

[minorwork]

to be alive something must be able to reproduce and also able to evolve.
look up rna world hypothesis

I'm something but I guess I must be dead. I can't reproduce. Mules must be dead too.

Tuff to define life, it is. Is there life on Mars? What would qualify? What does it mean to say something is alive as distinguished from it being dead? You'll only find a priori answers that don't exist empirically. No big deal. Just choose the relevant to the problem definition.

 

[granpa]

I certainly hope that was a joke.
I was, of course, referring to species not individuals

in some rare cases it may be hard to say exactly where one species ends and another begins but that doesn't change anything.
http://en.wikipedia.org/wiki/Ring_species

 

[Nienstien]

Just to clarify there is no standard model of the origin of life yet. Free to be discovered.

 

[minorwork]

I certainly hope that was a joke.
I was, of course, referring to species not individuals

in some rare cases it may be hard to say exactly where one species ends and another begins but that doesn't change anything.
http://en.wikipedia.org/wiki/Ring_species

I was hoping YOU were joking or just imprecise. And now your claim is that only species possesses life. Not individuals. Your imprecision continues.

 

[madcat8000]

I think the simpleist example of life would be to say a living organism takes advantage of disequilbrium in its environment to gather energy, copy itself, and has some "semi-stable" way to store heritable information, that is to say that the information about itself is generaly stable but has a factor that can allow it to change. It definitvely doesn't have to have DNA nor a Carbon structer. Might even be a machine.

 

[granpa]

oh. I see that you are joking.

 

[LivaN]

to be alive something must be able to reproduce and also able to evolve.
look up rna world hypothesis

Don't species evolve? Can an individual evolve?
If every human suddenly died except for myself, would I be able to reproduce? Would I be able to evolve? Am I still alive?

Surely a scientist could hypotheticaly create an organism with a brain and nervous system that has no possible way to reproduce. Would this organism be alive?

If a machine is created (year 4041?) , that has an artificial brain that is equivilant of a humans. This machine is self aware, can never die, cannot procreate, is it alive?

Your definition of what is alive is flawed!

 

[madcat8000]

Nein it is only the potential for reproduction and evolutionary differention that matters. The last man on Earth has the potential for reproduction just not the ability. Still alive. The self aware computer that has no internal ability to reproduce may be a valued member of society but is not alive.

 

[LivaN]

Nein it is only the potential for reproduction and evolutionary differention that matters. The last man on Earth has the potential for reproduction just not the ability. Still alive. The self aware computer that has no internal ability to reproduce may be a valued member of society but is not alive.

So a synthesized biological entity that is for all intensive purposes the identical of anyone one biological entity on earth, aside from its lack of ability to procreate, is by your definition not alive?

So if your dna was sampled and used to create a copy of you, with all your potential for procreation removed from the copy...would it be alive? It is then given your memories (it is the year 4041 after all). Is it still not alive? If someone were to destroy this copy of you, would it be murder? How can it be if it is not alive?

I'm sorry, but being self aware is grounds for being alive. Everything that is self aware is alive. Period.

 

[Borek]

10 posts ago I wrote that there is no one widely accepted definition of what is alive and what life is. Beat it as long as you want (biologists do it for decades), you will not get to any better conclusion that you agree to disagree.

 

[madcat8000]

You seem to be confuseing your personal morality with scientific fact. Self awareness only means that it qualifies as an individual. Give it all the rights and respect you want, can't make it a lifeform. And there fore not alive.

 

[LivaN]

10 posts ago I wrote that there is no one widely accepted definition of what is alive and what life is. Beat it as long as you want (biologists do it for decades), you will not get to any better conclusion that you agree to disagree.

I think you're right.

I can't however imagine any definition, of what is alive, leaving out self awareness as a garentee of being alive.

 

[bobze]

10 posts ago I wrote that there is no one widely accepted definition of what is alive and what life is. Beat it as long as you want (biologists do it for decades), you will not get to any better conclusion that you agree to disagree.

Good posts Borek.

There isn't a "natural" definition of life, no "law" of life.

Life is a human imposed definition on nature, we need such a definition to have meaningful discourse on life but that doesn't mean scientists don't understand the limitations of the definition (an an important aspect of defining anything in science is to understand it's limitations).

Biologists typically roll out a definition of life that looks something like;

1. Capable of reproducing with fidelity
2. Capable of converting energy from one form to another
3. Capable of dealing with metabolic waste
4. The cell is the smallest unit
5. Capable of biological evolution

Of course, this means that many "organisms" would fall into a shades of gray kind of deal where our definition of life is concerned. Like certain Mycobacteriums, Chlamydia or viruses.

Probably the most "simple", accurate and inclusive definition of life we could come up with is something capable of evolution (specifically by natural selection as NS is required for adaptive evolution).

 

[LivaN]

You seem to be confuseing your personal morality with scientific fact.

No, just trying to make logical sense of the term alive, and the context it's used in daily.

Self awareness only means that it qualifies as an individual. Give it all the rights and respect you want, can't make it a lifeform. And there fore not alive.

My bad, I should have left out the murder thing.


So you could exist without being alive? Interesting angle.

But then, could I argue that my mental processes be included in your definition?

takes advantage of disequilbrium in its environment to gather energy, copy itself, and has some "semi-stable" way to store heritable information, that is to say that the information about itself is generaly stable but has a factor that can allow it to change.

To a good degree, my mental processes follow your definition. They take advantage of the environmet (grey matter), they propogate, I am stable but overtime my mental processes "evolve"...would that work?

 

[granpa]

So a synthesized biological entity that is for all intensive purposes the identical of anyone one biological entity on earth, aside from its lack of ability to procreate, is by your definition not alive?
.

but it can procreate by synthesizing another.
That makes it a member of a species that is by definition 'alive' and therefore it is 'alive' too.

Nobody said procreation had to be done biologically.

 

[LivaN]

but it can procreate by synthesizing another.
Nobody said it had to be done biologically.

If the biological entity were say a mouse, then it couldn't. Well not by itself. It would need the scientist that created it to create more!

I think we are going about the definition differnetly. You look at what the definition currently appleis to, ie all life on earth, and then are trying to draw in the similarities to derive a definition.

I'm looking at the intended meaning of the word "alive" and then trying to define the meaning. I think it is more the "intention" that should determine if something is alive.

Two organisms (cats?) standing next to each other. One has the potential to procreate. The other does not and never will. Bother are otherwise identical. I just cannot logically conclude that one is alive and the other is not.
If I did, then to me "alive" is somewhat the equivilant of "replication", in which case there must be another word to define the similarity of the cats with respect to two stone cats.

 

[Siv]

The line between living and non-living is not as clear cut as we think it is. Life is the label we give to a certain type of complexity which involves replication.
Its a spectrum, really.
Viruses are actually in the fuzzy middle, its hard for people to categorize them clearly either way.

 

[Evo]

If the biological entity were say a mouse, then it couldn't. Well not by itself. It would need the scientist that created it to create more!

I think we are going about the definition differnetly. You look at what the definition currently appleis to, ie all life on earth, and then are trying to draw in the similarities to derive a definition.

I'm looking at the intended meaning of the word "alive" and then trying to define the meaning. I think it is more the "intention" that should determine if something is alive.

Two organisms (cats?) standing next to each other. One has the potential to procreate. The other does not and never will. Bother are otherwise identical. I just cannot logically conclude that one is alive and the other is not.
If I did, then to me "alive" is somewhat the equivilant of "replication", in which case there must be another word to define the similarity of the cats with respect to two stone cats.

You have already been given excellent explanations above. bobze explained it very well in post 26. You are hand waving, which doesn't belong in this forum.

 

[granpa]

Well you have a point but that is exactly why I said earlier that it was better to stick to defining a living 'species'.
Then we can just say that some individual is or is not a member of a living species.

English is a very poor language.
You are confusing a species that is 'living' and an individual that is a product of a 'living' species. In english we call both 'alive'. But they are really very different things.

my ability to walk and talk and metabolize and reproduce dying cells can be called 'alive' but its really very different from a species being 'alive'.

 

[granpa]

as usual my words have been twisted here and taken out of context.
I try to be helpful and point out that the capacity for reproduction and evolution are intimately tied to the concept of 'alive' as we usually think of it (which is something that I know for an absolute fact) and all I get is grief for it.
You people are a pain in the *** to try to talk to.
I don't know why I even bother any more.
You people ask for information then when its given you argue and bicker over every last single word.
Stop being so damned argumentative and try listening for a change.

there is a grey area where its going to be hard to say exactly where living ends and nonliving begins and you people will probably go on arguing over it forever. But the general rule when we look at nature is that 'life' as we normally think of it is the process of reproduction and evolution. this rules out crystals. it rules out fire.
it includes that first RNA-like molecule that somehow began reproducing itself.

A mule, even though it is a dead end, can nevertheless be said to be a part of that process.

the bottom line is that the word 'life' has as its core meaning 'the process of life' which has at its core the process of reproduction and evolution.
Beyond that core process the process of life could be said to include things like mules that can't reproduce but can reproduce their own dying cells. (I think there should be a different word for that though)
Likewise, beyond the core meaning, the word 'life' can be used loosely to include anything that has some of the properties (like consciousness) of things that we normally think of as being alive.

Now I am sure you will all pick my words apart and attack every uncrossed t and every undotted i.

 

[cosmos 2.0]

Good posts Borek.

There isn't a "natural" definition of life, no "law" of life.

Life is a human imposed definition on nature, we need such a definition to have meaningful discourse on life but that doesn't mean scientists don't understand the limitations of the definition (an an important aspect of defining anything in science is to understand it's limitations).

Biologists typically roll out a definition of life that looks something like;

1. Capable of reproducing with fidelity
2. Capable of converting energy from one form to another
3. Capable of dealing with metabolic waste
4. The cell is the smallest unit
5. Capable of biological evolution

Of course, this means that many "organisms" would fall into a shades of gray kind of deal where our definition of life is concerned. Like certain Mycobacteriums, Chlamydia or viruses.

Probably the most "simple", accurate and inclusive definition of life we could come up with is something capable of evolution (specifically by natural selection as NS is required for adaptive evolution).

Don't you think most important part, that should be included in this list is genetic material (RNA or DNA), without which a cell cannot function. The argument about virus is pretty blurry whether it is alive or not.

viruses contain genetic material, also they replicate using a host (not self replication). viruses could be considered as carrier of genetic material but have no metabolic processes, capable of mutation , replication using a host hence its below a cell (smallest unit ).

 

[johng23]

I'm sorry, but being self aware is grounds for being alive. Everything that is self aware is alive. Period.

How are you defining "self aware"? Does it just mean the system responds to stimuli in an extremely compicated fashion? Because otherwise I don't even know how you expect to prove that other humans are self-aware, let alone a machine. I'm not saying solipsism is a tenable philosophical position, but it's outside the realm of science to address the question as far as I can see.

 

[jgm340]

We already have computer programs which can self-reproduce: viruses.
Some even "evolve", randomly changing bits to avoid detection.

The only ways one might separate computer viruses from "life" proper are the following:
1) Computer viruses depend on an existing system (namely, computers of a particular architecture running the same software connected over networks).
2) Computer viruses had a creator, and did not arise spontaneously.

But (1) is not really a good argument, as humans depend just as much on their environment!

For example, oxygen was not "naturally" present in the Earth's atmosphere. Life didn't start out using oxygen: it was actually a poison which violently disrupted processes (just like it does today with forest fires). Bacteria actually filled the atmosphere with oxygen, and paved the way for further life to take advantage of it as an energy source: http://www.palaeos.com/Earth/Atmosphere/oxygen.htm

Aside from this, humans depend on trees, fish, cows, etc. just to stay alive. If you think about it, we can exist only in the narrowest of possible environments. So how is it fair to say that a biological virus isn't "alive" because it depends on human cells to do it's work for it, while we depend on plants to collect energy for us? How is it fair to say a computer virus isn't alive just because it depends on computers?

For number 2), why would we care how it was created? In fact, a lot of you are even arguing that one of the defining characteristics of a living thing is that it was created by another living thing (by reproduction)!

Humans and mosquitoes, along with some ancestral protist, worked to "create" the protist that causes malaria. Sure, there was a lot of "guess-and-check" involved with random genes mutating and reordering, but the malaria protist was certainly more likely to be "created" recently rather than 2 billion years ago (back when it's immediate ancestors and humans didn't exist).

In this sense, evolution is "intelligent" and "creative". Evolution is NOT just natural selection acting on randomly created possibilities.

The possibilities (as in DNA sequences) are created "intelligently" by the life that exists today. When you have a baby, it's more likely than not to have most of the great qualities you have. Certain sequences of DNA are far more likely to be created than others, meaning that the possible life forms on which natural selection acts are to no fathomable degree created randomly or spontaneously.

So, if a person writes a program, or genetically engineers their own organism, there's no rational way you can separate this from "natural" life on the basis of it being created.



Anyway, so here is my definition for life:

Life is a process which uses an external energy source in a controlled and roundabout way to decrease entropy locally, (rather than doing so in a quick, violent, and straightforward chemical process that increases entropy locally).

This definition has a lot of nice properties:
1) It rules out a lot of things which clearly aren't life, such as fire, and almost all non-life chemical reactions.
2) It gets to the core of what we think about when we think of life: controlled, organized chemical reactions. If a process is causing really organized glucose molecules to be formed in an otherwise disorganized slew of random molecules, then chances are it's alive.
3) There is no question that someone who can't reproduce is indeed alive.
4) It doesn't needlessly rule out non-DNA/RNA based life.

 

[Borek]

Don't you think most important part, that should be included in this list is genetic material (RNA or DNA), without which a cell cannot function.

That will mean limiting the definition to the life as we know it on Earth. That's not necessarily bad, we don't know other forms of life, but trying to start a general definition by narrowing it down to specific case doesn't sound logical to me.

 

[granpa]

Life is a process which uses an external energy source in a controlled and roundabout way to decrease entropy locally, (rather than doing so in a quick, violent, and straightforward chemical process that increases entropy locally).

doesnt a refrigerator do that?

 

[granpa]

I would like to point out that the original question was where does life come from.
Not what is the definition of life.
'life' as a physical process is different from 'life' as a word in the english language.

life as a physical process comes from reproduction and evolution.

the definition of the word 'life' is a completely different question especially when you consider that words are often used loosely to mean things very different from the core idea. (I personally think we should have a separate word for things that can't reproduce but have all the other attributes of life (self-maintenance) and another word for deliberate behavior directed toward self-preservation)

much of the arguing here just seems to be semantics.

 

[bobze]

Don't you think most important part, that should be included in this list is genetic material (RNA or DNA), without which a cell cannot function. The argument about virus is pretty blurry whether it is alive or not.

viruses contain genetic material, also they replicate using a host (not self replication). viruses could be considered as carrier of genetic material but have no metabolic processes, capable of mutation , replication using a host hence its below a cell (smallest unit ).

No, because including DNA or RNA works on the a priori assumption that categorically all "life" would replicate in such ways. It is an a posteriori assumption that life is inexorably linked to these two nucleic acids and its not beyond the realm of possibility that in some dark and forgotten chasm of Earth there exists life which does not use DNA/RNA as a means of heritability (though small) and it is almost certainly a poor assumption to make for when and if we get out into the cosmos.

Really, as Granpa pointed out, the unifying feature of life and things which are life-like is the ability to evolve by natural selection. Again, as NS is the means for adaptive evolution and the conquest of biological complexity.

As I pointed out viruses "live" (pun intended ) in one of those shades of gray, between "living" and "nonliving". There are in deed cells which make their home here as well, Chlamydia, Rickettsia and species of Mycobacterium are obligate intracellular parasites--That is to say they are incapable of reproduction with fidelity outside of a host cell. Alive? How about another shade of gray.

Prion proteins 'reproduce' by a kinetic trap (an application of Le Chatelier) and are capable of natural selection acting upon them. Here there is "no" DNA/RNA transmitting hereditary material, rather changes in protein folding (alpha helica dominated or beta sheet dominated) which confer selective advantages to new "generations" of prions. More shades of gray.

So what we have, despite human-imposed definitions, is a continuum or spectrum (as someone else put it) going from something "not-living" to something with "life-like properties" to something we define as "living". The only unifying factor along that pathway is whether the "organism" (be it some primordial theoretical molecule or a modern cell) meets the criteria for natural selection; Namely, differential reproductive (replicative) success in a population of these organisms and introduction of variation at generational boundaries.

Meeting those two criteria then, NS can build upon any system layers of complexity that leads to some population of organisms we may wish to define as "living".

Edit: I see Borek beat me too it!

 

[cosmos 2.0]

That will mean limiting the definition to the life as we know it on Earth. That's not necessarily bad, we don't know other forms of life, but trying to start a general definition by narrowing it down to specific case doesn't sound logical to me.

It wouldn't be limiting. The general idea is, that life should carry on functioning in a conducive environment and able to pass on the blueprint to the next generation (with alterations if required) with which it was previously successful.That is done by RNA or DNA.As far i know, there is no organism including viruses that does not contain rna or dna m

 

[jgm340]

doesnt a refrigerator do that?

A refrigerator does not locally decrease entropy in a roundabout way.

It does so in a rather direct way. Similarly, when a crystal forms, it does so in a direct way, involving simple processes.

If you look at a living cell, on the other hand, it involves complicated enzymes and catalysts, and many steps before a waste product is generated. Something fits the definition of life better as the number of steps before a waste product is produced increases.

Moreover, the relative decrease in entropy is SO slight. The refrigerator itself has so much structure for just a small decrease in the random movement of a tiny number of air molecules.

A cell, on the other hand, has structure 99.999% of which would not exist had not the process by which the cell acts occurred. In other words, the processes which go on in the cell are the sole reason for the existence of much of its structure. Had the processes in the cell not occurred, much of that material would just be floating randomly about.

The fridge would still have been a giant hunk of organized metal, however, if it were never plugged in. Remember, life is a process, not a thing.

 

[granpa]

and what about the first primitive self-reproducing RNA-like molecule.
It was presumably surrounded by a sea of its subunits (which presumably had a natural tendency to stack in one dimensional structures) so all it had to do was arrange those units in some order.
Thats not exactly complicated.

 

[granpa]

life certainly does reverse entropy and over time as it evolves it becomes more and more complicated.
thats evolution.

but i don't think that being complicated is itself fundamental to the process of life
being complicated just follows from having genetic material and the ability to reproduce and evolve.

if on the other hand you are trying to define the word 'life' then that would be a semantic matter
and I really don't want to get into that.

you seem to be looking for something that is common to all the things that we use the english word 'life' to describe.
That is more semantics than physics.
When you learn a foreign language you learn that many things that are only 1 word in english are in fact 2 totally different things and are 2 words in the foreign language.
There is no reason to assume that all the things that we describe with the english word 'life' are in fact a single unified concept.

 

[cosmos 2.0]

No, because including DNA or RNA works on the a priori assumption that categorically all "life" would replicate in such ways. It is an a posteriori assumption that life is inexorably linked to these two nucleic acids and its not beyond the realm of possibility that in some dark and forgotten chasm of Earth there exists life which does not use DNA/RNA as a means of heritability (though small) and it is almost certainly a poor assumption to make for when and if we get out into the cosmos.

is there any evidence here on earth, any other form of life (without Rna or dna) exists ?
I have nothing against broadening the scope to define life. But while broadening , we should realize the limits nature puts on kind of life that can exist and be successful

Prion proteins 'reproduce' by a kinetic trap (an application of Le Chatelier) and are capable of natural selection acting upon them. Here there is "no" DNA/RNA transmitting hereditary material, rather changes in protein folding (alpha helica dominated or beta sheet dominated) which confer selective advantages to new "generations" of prions. More shades of gray.

These are recently discovered group of proteins. we should make a distinction between ones that have genetic material and one that do not.
Are these proteins transmitted similar to any viruses , ricketsiae or mycobacterium. Can they be cultured or grown in the Lab like viruses or bacteria.
In the true sense they do not replicate, but converts already existing proteins and accumalates.

So what we have, despite human-imposed definitions, is a continuum or spectrum (as someone else put it) going from something "not-living" to something with "life-like properties" to something we define as "living". The only unifying factor along that pathway is whether the "organism" (be it some primordial theoretical molecule or a modern cell) meets the criteria for natural selection; Namely, differential reproductive (replicative) success in a population of these organisms and introduction of variation at generational boundaries.

Meeting those two criteria then, NS can build upon any system layers of complexity that leads to some population of organisms we may wish to define as "living".

well it all goes back to the origins of life, which is still not known as to whether complex molecules assembled themselves or any other way life organized itself.e continues we may never know.But one thing is clear Dna or Rna led to increase in complexity in the way life organized itself.

 

[jgm340]

and what about the first primitive self-reproducing RNA-like molecule.
It was presumably surrounded by a sea of its subunits (which presumably had a natural tendency to stack in one dimensional structures) so all it had to do was arrange those units in some order.
Thats not exactly complicated.

And it's questionable whether that would be considered life, or just part of the non-life processes which eventually led to the more complicated processes we call life. I'd go with the latter.

If we were to try to pinpoint the absolute first process which one could call life under my definition (indecisive as it is), it would probably be at the moment at which the probability of more complicated processes arising from existing processes became significant enough that it was almost certain that in the next month or so, something we would surely call life would exist.

 

[granpa]

well you seem to have made your mind up so I will stop trying to reason with you.

 

[Borek]

It wouldn't be limiting.

Yes it is limiting. Have you heard about PNA, p-RNA, and TNA?

http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=189

These we already know, plenty of other possibilities.

That is done by RNA or DNA.As far i know, there is no organism including viruses that does not contain rna or dna m

You are all the time presenting definition that is limited to the life as we know it. Or as you know it

 

[granpa]

the capacity to reproduce and evolve is necessary and sufficient for life to get started on any world. Everything after that is philosophy.

 

[jgm340]

well you seem to have made your mind up so I will stop trying to reason with you.

Don't be like that. You made a claim about the nature of life, which I didn't think accurately represented it. I offered an alternative definition.

Perhaps "complicated" could be replaced by something more accurate and meaningful. I want a condition that captures the fact that life seems to have an ulterior motive.

Although it feeds on an energy gradient, it's purpose is not simply to deplete that energy gradient.

Life *wants*, in some sense, its own processes to occur, in the same way that dried wood in the hot sun *wants* to burn, or how water *wants* to form a crystal when it gets cold. The formation of crystals and the combustion of flammable materials is tied directly with the basic chemical and physical properties of the materials involved. Any statement about the crystals "wanting to form" can be translated readily into a statement about water molecules having certain properties.

When one asks, however, "why does a cell seem to want to reproduce?", or "why does a cell seem to want to make these proteins?", the answer could not possibly boil down to a statement about the properties of a few common molecules. Any answer would involve not only an uncommon collection of molecules, but also the structure of the cell, many strange interactions working symbiotically, and many facts about its ancestors.

When one asks, for example, "why does this cell seem to want to reproduce?", you can't really understand it by only looking at that cell. I mean, reproduction is expensive energy-wise. The best answer I can think of is that statistically speaking, you are much more likely to come across a cell that wants to reproduce than one which does not: almost all cells in existence were created by other cells which must have had the ability to reproduce.

I feel as though a definition of life ought to capture that aspect of complexity, while ruling out static results of life, such as art, music, etc.

Then again, the concept of "memes" as ideas with a life of their own may be an important concept for higher life. After all, what makes someone human has a lot to do with what they learn. Intellectual thought seems like a self-perpetuating end in itself. Perhaps consciousness is a form of life itself...