News flash! Neither DNA nor RNA required for evolution.

[Rum]

I suspect the question of replication and evolution is separate from whether something is 'alive' which may have more to do with our own prejudices about (maybe) consciousness, the possession of a nervous system? One can hypothesise circumstances where self replicating complex molecular structures adapted to their environment and 'evolved' to quite high levels of complexity without being alive in the sense we tend to mean it.

As ever, in ignorance in this area.

[JimC]

I suspect the question of replication and evolution is separate from whether something is 'alive' which may have more to do with our own prejudices about (maybe) consciousness, the possession of a nervous system? One can hypothesise circumstances where self replicating complex molecular structures adapted to their environment and 'evolved' to quite high levels of complexity without being alive in the sense we tend to mean it.

As ever, in ignorance in this area.

Well, viruses are widely accepted as being alive, without the slightest bit of consciousness or nervous system.

...self replicating complex molecular structures adapted to their environment...

They would be life, Rum, even if it's not as we know it...

Self replicating, and with a complex internal structure which clearly is an adaptation to environmental pressures brought about by some form of natural selection, with the usually component of random chance thrown in, and we have life, whether it looks anything like life on earth...

[Rum]

I suspect the question of replication and evolution is separate from whether something is 'alive' which may have more to do with our own prejudices about (maybe) consciousness, the possession of a nervous system? One can hypothesise circumstances where self replicating complex molecular structures adapted to their environment and 'evolved' to quite high levels of complexity without being alive in the sense we tend to mean it.

As ever, in ignorance in this area.

Well, viruses are widely accepted as being alive, without the slightest bit of consciousness or nervous system.

...self replicating complex molecular structures adapted to their environment...

They would be life, Rum, even if it's not as we know it...

Self replicating, and with a complex internal structure which clearly is an adaptation to environmental pressures brought about by some form of natural selection, with the usually component of random chance thrown in, and we have life, whether it looks anything like life on earth...

Well I refer you to earlier posts which suggest that defining what 'life' is exactly is not easy. I have read (I am not *totally* ignorant on this) that viruses can be classed as both - given that they achieve what you might call 'life status' when they invade an organic cell.

[JimC]

Rum wrote:

Well I refer you to earlier posts which suggest that defining what 'life' is exactly is not easy. I have read (I am not *totally* ignorant on this) that viruses can be classed as both - given that they achieve what you might call 'life status' when they invade an organic cell

It's certainly true that when viruses are "between cells" they are totally inactive, and have many properties that could be described as crystalline. Also, most other life forms have a complex internal metabolism utilizing energy and materials from outside, which viruses lack. However, the broad concensus in modern biology would be that the ability to replicate (with potential for variation) is the key feature of life, allowing viruses to fit within this "broad church" definition of life.

In many ways, prions are a better example of an entity which challenges such definitions of life. When a prion triggers a cascade of aberrant protein folding in its own "image", is it truly replicating...

[Xamonas Chegwé]

Life is a semantic fiction. It is a convenient way of grouping together certain structures that self-replicate and appear to have some kind of motivation in doing so. The fact that a phage virus has no more motivation in replicating itself via the cell structure of a convenient bacteria than Phenolphthalein has any motivation of locating H+ ions in solution in order to lose its pink colour is conveniently ignored.

We, ourselves, are nothing more than huge and rather inefficient (although relatively successful) machines for replicating human DNA. That we are able to write that fact down is a mere byproduct!

[trubble76]

It seems to me that the definition of life bares a resemblance to the definition of temperature, insofar as on the macro scale it is a vitaly important measurement, however when seen on a micro scale becomes irrelevant.

At these micro scales, it seems that life/not-life becomes irrelevant. "Micro-creatures" whether they be human cells, or prions simply follow the rules of chemistry. I think discussions on the definition of life is a purely philosophical pursuit.

As it is philosophical in nature (i assume you all agree with me ), i think the interest lies in those that believe that all life is sacred. Does the "killing" of viruses/prions/bacteria/etc count as the taking of life? Any Buddhists out there that actively attempt to spare the life of these critters?

[FBM]

It seems to me that the definition of life bares a resemblance to the definition of temperature, insofar as on the macro scale it is a vitaly important measurement, however when seen on a micro scale becomes irrelevant.

At these micro scales, it seems that life/not-life becomes irrelevant. "Micro-creatures" whether they be human cells, or prions simply follow the rules of chemistry. I think discussions on the definition of life is a purely philosophical pursuit.

There's no clear place to draw the line, is there? Yes, it's philosophical, I suppose. Even biologists who try to answer the question are most likely doing it out of curiosity, rather than for any practical concerns.

As it is philosophical in nature (i assume you all agree with me ), i think the interest lies in those that believe that all life is sacred. Does the "killing" of viruses/prions/bacteria/etc count as the taking of life? Any Buddhists out there that actively attempt to spare the life of these critters?

Eh...that's not a Buddhist ideal.

[trubble76]

As it is philosophical in nature (i assume you all agree with me ), i think the interest lies in those that believe that all life is sacred. Does the "killing" of viruses/prions/bacteria/etc count as the taking of life? Any Buddhists out there that actively attempt to spare the life of these critters?

Eh...that's not a Buddhist ideal.

Apologies then, i had it explained to me by some Buddhists in Malaysia that Buddhists are encouraged to actively avoid the taking of any life. I suppose i shouldn't have believed them. Meh.

[FBM]

As it is philosophical in nature (i assume you all agree with me ), i think the interest lies in those that believe that all life is sacred. Does the "killing" of viruses/prions/bacteria/etc count as the taking of life? Any Buddhists out there that actively attempt to spare the life of these critters?

Eh...that's not a Buddhist ideal.

Apologies then, i had it explained to me by some Buddhists in Malaysia that Buddhists are encouraged to actively avoid the taking of any life. I suppose i shouldn't have believed them. Meh.

No, that much is true, but it's not because life is sacred; it's a training method to cultivate compassion. There's nothing truly sacred in Buddhism.

[trubble76]

As it is philosophical in nature (i assume you all agree with me ), i think the interest lies in those that believe that all life is sacred. Does the "killing" of viruses/prions/bacteria/etc count as the taking of life? Any Buddhists out there that actively attempt to spare the life of these critters?

Eh...that's not a Buddhist ideal.

Apologies then, i had it explained to me by some Buddhists in Malaysia that Buddhists are encouraged to actively avoid the taking of any life. I suppose i shouldn't have believed them. Meh.

Right, ok then, substitute "sacred" for "important" and carry on as if nothing happened.

[FBM]

Right, ok then, substitute "sacred" for "important" and carry on as if nothing happened.

What? Did something happen?

[JimC]

Right, ok then, substitute "sacred" for "important" and carry on as if nothing happened.

What? Did something happen?

Happening is an illusion...

(though quite a useful one for hominids in a dangerous world...)

[Random Mutant]

I suspect the question of replication and evolution is separate from whether something is 'alive' which may have more to do with our own prejudices about (maybe) consciousness, the possession of a nervous system? One can hypothesise circumstances where self replicating complex molecular structures adapted to their environment and 'evolved' to quite high levels of complexity without being alive in the sense we tend to mean it.

As ever, in ignorance in this area.

I profess similar ignorance, although I did biology in high school. I remember MRS GREN was the accepted schoolboy definition of what was alive:

M: Movement
R: Respiration
S: Sensitivity
G: Growth
R: Respiration
E: Excretion
N: Nutrition

I realise the world has moved on since the 80's but it works as a rule of thumb. I don't think prions were even on anybody's shopping list, mad cow disease was still being invented then...

[Chinaski]

A biologist from another forum I visit said this:
"No, it does not make abiogenesis an inevitability. This study demonstrates that a protein can evolve independently of nucleic acids, but the current model for early life is still an 'RNA world', which posits that RNA came before enzymatically active proteins."