So, yesterday, Froggy and me were hanging out, and we got onto the subject about evolution and about us being tailored to the world we're in and being comprised of things and powered by things that are common too the world we live in.

That got me think about how we define what is 'biological' in such crude ways, as the type of matter it is made from (carbon).

And life being defined by such things as an organism that respires and replicates in some manner or another.

This led me to my next thought which started this post.

What would it take for something man made to be considered alive? No one would call a computer program alive, but what about a super smart one? And if not why not? And if so, what magical level of intelligence do we stop seeing it as inanimate and decide it's alive. A computer program certainly doesn't meet any of the official terms of life that's for sure.


Let's use an example; nano technology. The idea of building micro and nanoscopic little machines that can,
a ) perform a certain function, like repairing arteries or building microchips, and
b ) replicate more of themselves.
In my mind that doesn't seem that dissimilar to microscopic single cell organisms. It probably wouldn't respire in the same way single cell life traditionally does, (although different cells respire using different methods) and would make exact copies of it self, which unlike large multicellular organisms. Single cells do replicate without needing a second cell, and also create perfect copies of themselves under normal circumstances, as opposed to genetic mixing with partners.

This also led me to another interesting thought. That would mean flaws in the replicating of nano robots could allow nanobots with advantages flaws to out build the original versions. They'd be able to in effect evolve.

Before someone jumps in and says 'but we can't just mess with the definition of life'. Not all of what we class as alive even meets it today. The example being virus' or virii. They don't respire! That's right, they are entirely dependant on the laws of chance to deposit them in the right place to infiltrate other cells and produce more versions of themselves.

So back to my original question. Could anything we humans build (not using our in built sexual organs) ever be considered alive, and at what point would we consider them so, if so at all?

I learnt an interesting fact the other day.

You all know that there are computers that can beat the best human chess players in the world, and its quite a big event when one of us fleshy things manages to be victorious. But did you know that there has not been a computer built that could beat a human Go player of even moderate skill at the game.

Go is the Eastern game that looks similar to Othello, except the board is huge, 19 by 19 squares, and the gameplay allows many combinations of legal moves so that it is boasted that no game of Go has ever been played twice. A computer thinks in numbers and logical moves, which a human can only do to a certain extent.

Anyway, if someone can build a replicant who can make me a sandwich and beat me at Go then I will no longer think of technology and humans merely touching finger tips but in a locked embrace.

What is interesting here is that you use intelligence as a factor for life - plants are not intelligent, nor are mosses, or bacteria. In my searchings for an answer to this complex question, I have found that there is only one thing that seems to be consistant with all life - All life strives to reproduce itself. All of an organism's life is somehow designed merely to reproduce itself as best it can. Even those organisms which cannot reproduce for some reason (like a mule) still seem to strive for it in many ways, if only tangentally.

It seems once again that Dave's beaten me to the good topic

Ok, so, it should be said that from the time I started learning about biology, my favorite topic has been life and evolution.

That being said, however, I do believe that the current definition of life needs to be updated. And there really is no "messing with the definition of life" as such, since we didn't create it before we discovered life, but rather used it to classify what we saw. It's a work in process, like anything scientific.

Anyway, for the process of debate, let's look at the actual definition of life (courtesy of Wikipedia)

The characteristics of life:

are that they are cellular, carbon-and-water-based with complex organization, having a metabolism, a capacity to grow, respond to stimuli, reproduce and—through natural selection—adapt.

Now, for purpose of debate, let's compare your example of (as I like to call) life's outcast, the virus.

A virus is/can:

-A cell (dependsing on definition of cell)
-responds to stimuli
-reproduces
-evolves

That's about it.

Now, if we could build a computer that could do all of that, would it be considered life? Or at least if it covered Dave's requirement of purely reproducing? In my opinion, that's a rather fine line to walk upon.

Consider a computer virus. It's only prupose is for it to reproduce itself. Would that be considered life then? Most people would say no, because it's man-made. So could a loose definition of life be something that strives to reproduce, but does not need to be man made? Of course this could end up excluding mammals such as mules which are (depending on your definition) man-made. Or maybe it would be more of a "life not fully created by man," but then that would require a full definition of life!

ahh.....I love this stuff.

The problem with that definition is it could include stuff we don't consider alive, like fire.

I think the striving to reproduce characteristic is just an adaptative thing - if there is no drive to reproduce then the species will die out. I guess this is true for most of the criteria for life; they seem to describe the features a group of things needs to be considered a succesful species, rather than what a member of that species needs to be a living thing. But what about really badly adapted life? If something was born with lots of strange mutations so that it couldn't do many of the things we think life should do, then wouldn't it still be alive, even if it only survived ten minutes?

I kind of like the definition of life in terms of entropy. I'm not gonna try and explain it because thermodynamics confuses me.. but using that definition the whole earth can be seen as alive (gaia theory) which some people disagree with, but it's quite interesting.

I think that if computers and robots and things meet whatever criteria we decide to be neccesary for something to be life, then we should accept it rather than spend ages thinking up new characteristics for life, just cause robots are cool plus, does it really matter what we decide is life and what isn't? If we can't decide on a suitable definition then we should make a new website "life or not" where people can vote for the lifeiest things...

Argh.. trunks_girl26's post made my brain do backflips trying to ponder over computer virus' and stuff.

But yeah if drive for reproduction is what decides life, then a load of things like computer virus' suddenly seem alive (and I'm not saying they don't).



See people like me can't accept that. I need reasons for things to be thought of in one way or another, my brain and mind doesn't allow for people that say "because I said so" .

Things on my list of things that seem to fall into various categories of 'are they or aren't they alive' are:

The Sun (and stars in general)
Fire
Crystals when their growing
..and even people from Florida (I'm joking!)

A change in the definition would be nice, although I can't see what use it would have, unless something we traditionally consider inanimate but intelligent, we decided needed rights or what not.

My original draft of the post, which was deemed too silly to post, was about fire. I was told things had to move, reproduce, respire, excrete, grow and some other things to be classified as life.

Fire moves, could reproduce if you touched two pieces of fuel together creating two different fires, it converts oxygen to carbon dioxide (way before I learned Krebs had a bicycle), it leaves ash, it can grow larger. Fire really confused my idea of GCSE biology for a while.

My Understanding of what constitutes life (purely on a scientific level) is as follows (please forgive me as this is dredged from 15 year ago GCSE lessons)

M Movement
R Reproduction
G Growth
R Respiration
I Irritability
N Nutrition
E Excretion

I think I'd have to (if I stretch my mind a bit) equate fire's reproduction to a plant's budding. Essentially, it's part of the main fire, but if it gets cut off it can create a seperate being.

That being said, however, I don't think I could classify fire as life, seeing as fire at it's most basic level is just one big chemical reaction. Life, on the other hand, is a series of dependent chemical reations. I also don't believe that fire aspires to reproduce, rather, it just kind of happens at random.

This is an important point. When I say that live strives to reproduce, it is because I feel that nearly every basic action is undertaken to increase the chances of successful reproduction on an organism's part. This breaks down at the highest intelligence levels (to a degree) but for the most part it holds true. Fire, however, does not make any attempt to change how it functions to reproduce.

Well Virus' are interesting here again... since they are inert, they have no method of moving themselves and are infact mere floating strings of RNA (cousin of DNA). Some people argue that they're not life, and are just inert matter that multiplies on contact with more complicated biological structures.

It came into existence as basically microscopic dirt that just gets multiplied along with the cells normal functions when it falls into it's nucleus. Odd changes in it's structure make some better at going through this process than the rest.

It satisfies less of the official "what makes life" criteria than many many things considered nothing but inert, or 'dead'.

The result is our immune systems can't actually kill it as such since it doesn't work in that way, it's just neutralised with anti bodies by coating the virus particles with them. (tis fascinating stuff).

I don't reallt hink fire's alive either, but I struggle to see what makes it not alive considering the things we do consider alive.

However here you have the RNA strands simply using external methods to move. Why does it need another method? I suppose it's a bit like parasite in that respect. I would say that it pretty much fulfills most if not all the main criteria for life.

M Movement - It uses external methods to move, it doesn't really need anything else. Can anyone think of other life forms that rely on external methods to move? Maybe a Verruca or something? Or does that dig itself into the flesh?
R Reproduction - It replicates itself.
G Growth - As part of the process of replication, yes.
R Respiration - Hmmm... okay that's a tricky one. Not sure it does that.
I Irritability - It responds to external stimulus, so yes.
N Nutrition - It feeds of healthy cells, so yup.
E Excretion - I think that there is waste material left over once it has replicated itself, so yup.

However I wouldn't consider a virus alive for the same reason I do not consider DNA alive. It's just a protein strain. It contributes (or damages) life that it's part of, it has no other real ability. I don't think it evolves in the classical sense like a bacteria does. It just... is.

Yeah I know that's a rather weak argument but hey.

In a spiritual sense I suppose it has a spark of creation and perhaps life/divinity in it though... but so does fire and electricity.

I'm just curious how the movement applies to plants? Aren't plants pretty much stationary and wouldn't be considered life?

Tradtionally, movement isn't a characteristic of life, because of organisms like plants.

*points to her first post with the actual characteristics of life*


I hate to break it to you, Calantyr, but RNA and DNA aren't just protein strands. The very fact that it's able to replicate itself (something that no other protein strand can do) places it in a completely different category all together.

Movement: nope it don't move

Replication: Ok, I'm gonna go into depth on this because I had some thoughts on this. Let's say I had a photo of someone I liked a lot. I liked it so much I placed it into a photo copier and as if by magic I had produced 100 copies of that person that I could place in a shrine to them. I certainly wouldn't call photos a self replicating thing. The photocopier did that. That's a bit like virus' they are a a set of instructions to make more of themselves. They need a cell to infiltrate to the manafacture additional cells, and it's the cell they infiltrate that does the creation. On their own though, given all the materials nessecary they would do nothing.

Growth: Well growth and replication are too different things. They don't gain any physical size in their life cycle, so they don't grow.

Respire: Don't do that either

Irritability: They don't respond to external stimuli. As in they don't change their actions based on situation. Since they don't move, excrete, fire off electrical activity, grow, run, or even activily seek out cells. They don't really respond. They literally by the luck of sheer overwhelming numbers end up filling all available space, through the above method of infiltrated cells spewing them out on mass.

Nutritions: a tricky one you could argue that it needs cells to replicate more of it self, and that on some level we all need that. But then you could argue that the cell it infiltrates isn't actually killed, it's just reprogramed to another means, and since the virus doesn't actually take anything from the cell it infects. It can't be drawing sustenance. So both ways.. well kinda work. Dunno. Iffy.

Excretion: nope they don't excrete, they enter cell, mass produce virus. The cell normally dies because neighbours of host kill it for being different. Or else because the cell ceases all normal functions and eventually starves to death. That's closer to suicide than viral waste. Otherwise we could say the US excretes out bombed out middle eastern countries. Amusing a phrase as that is. It's not true.


The thing about RNA and DNA is that, generation one of life (the basics of the basics), didn't have either. DNA and RNA came into existence most likely as without them, life can't send even the most simple improvements to it's descendants. Making it quite literally a blueprint rather than it's own entity.

Somewhere along that chain, Virus' came into existence, as RNA sequences that rather than spawning themselves, they kinda got other cells to make more of themselves for them (anyone else think that's so god damned lazy?) They certainly seem in the spirit of what makes life, and have been around for the majority of the time lifes been on earth. They just work on such a basic and fundamental different way because their evolutionary divide from what we consider the main vein of life was so early in life's history. They have differences on how they work, down to even the basic molecular level. Unlike say plants, which divided from us evolutionarily on the grand scheme of the age of the world fairly recently (theories say that the majority of the age of the world, the world never developed beyond the microscopic, large visible plants and animals are actually new features, compared to the age of life on earth.)

I've decided that virus' are alive, just the definitions are way too limited by the fact that we only consider things alive that have inherited a certain set of traits and method of getting things done. Virus' despite being a lot older than even plants, just happened to have divided from the main vein very very early, so wasn't on the band wagen to get nifty and neat features that we got, They did however gain super fast evolution, a side affect of spawning in such massive numbers.


However with it said that fundamental and basic, molecular differences in things not being a reason for things to not be alive, that opens the door to more and more things like the early mentioned computer virus' which are even more fundamentally different from the main vein of life, then normal virus' are.

Let's not get carried away here - Neither DNA nor RNA can replicate itself without a whole lot of other things. A DNA strand left on its own does nothing, an RNA strand left on its own does nothing. They need things to help them along.

Hmm... okay possibly. I need to read up on it some more.

However plants DO move. For example flowers will rotate to get as much sunlight as possible throughout the day.

They need help, yes, however, name one other protein strand that has the capacity to get itself replicated, help or not. There is a reason they're reffered to as the blueprint for life.




That's not considered movement under classical biological thinking, actually. It's called phototropism and is instead classified as a response to stimuli (Yes, it's rather silly, especially because tropism translates to movement), however, there are other organisms which don't move that are still considered life.