This is crazy - on the nature of life

[Humodour]

Most of us (except perhaps some Americans with their weird obsession with Creationism) learnt about viruses in biology class. We learnt about how they are technically not 'alive' but nonetheless came to consider them as 'close enough' due to their similarities to other living things (not to mention that they evolved from living single-cell organism).

 

Well, now kids in biology class are going to have to contend with prions as well - rogue self-replicating protein strands responsible for things like mad cow disease. As was, I guess, inevitable due to their ability to replicate/reproduce, it has been shown that prions also evolve (e.g. drug resistance).

 

Differences from viruses:

a) they don't have DNA/RNA because they didn't evolve from an organism (though they ARE made up of peptides like all proteins)

b) they aren't cell-based like all known viruses and organisms.

c) they reproduce by converting existing healthy proteins into diseased ones one at a time - this is unlike viruses, which can infect their host, create multiple copies of themselves, then leave/die (though often the host is simply fully consumed in the process)

 

http://www.physorg.com/news181466564.html

 

Anyway the reason this is so interesting is that it's a good example of evolution as a mathematical optimisation process rather than a biological process because this clearly demonstrates that you don't need nucleic acids (RNA/DNA) for evolution (as has been obvious to many computer scientists for a while now). Any self-replicating system exposed to randomness in its code will evolve.

 

Note: not just mammals are susceptible to rogue proteins - at least two forms of fungi are as well.

Edited January 3, 2010 by Krezack

[Pope]

Any self-replicating system exposed to randomness in its code will evolve.

 

Kind of obvious isn't it? Under the premise of course that the resources required to replicate are too scarce to support an entire generation. Only then can you get a selection, be it natural or not.

[Oblarg]

Any self-replicating system exposed to randomness in its code will evolve.

 

Kind of obvious isn't it? Under the premise of course that the resources required to replicate are too scarce to support an entire generation. Only then can you get a selection, be it natural or not.

 

Very obvious. When you think about it, there's really no way evolution can't happen in a self-replicating system subject to random mutation and external pressures.

[Purkake]

That's pretty much it.

 

Pack it up, Krezack, this thread is over.

[Volourn]

"Most of us (except perhaps some Americans with their weird obsession with Creationism)"

 

Bigot criminal.

Edited January 4, 2010 by Volourn

[Walsingham]

It is indeed interesting. I didn't know that about prions. However I was already of teh opinion that replicators evolve and due to my reading on evolutionary algorithms and so on.

[Humodour]

Any self-replicating system exposed to randomness in its code will evolve.

 

Kind of obvious isn't it? Under the premise of course that the resources required to replicate are too scarce to support an entire generation. Only then can you get a selection, be it natural or not.

 

That's not entirely correct though is it? (Which is actually detailed in the article). It's a common misunderstanding that evolution requires natural selection - it doesn't. If mutation is occurring, and even if there are no resource pressures, then if the mutant can survive and reproduce, it WILL (because, well, there's no pressure against it), forming sub-species.

 

Any self-replicating system exposed to randomness in its code will evolve.

 

Kind of obvious isn't it? Under the premise of course that the resources required to replicate are too scarce to support an entire generation. Only then can you get a selection, be it natural or not.

 

Very obvious. When you think about it, there's really no way evolution can't happen in a self-replicating system subject to random mutation and external pressures.

 

Obvious for us fortunately, but many science lay people should find this interesting.

[Pope]

Any self-replicating system exposed to randomness in its code will evolve.

 

Kind of obvious isn't it? Under the premise of course that the resources required to replicate are too scarce to support an entire generation. Only then can you get a selection, be it natural or not.

 

That's not entirely correct though is it? (Which is actually detailed in the article). It's a common misunderstanding that evolution requires natural selection - it doesn't. If mutation is occurring, and even if there are no resource pressures, then if the mutant can survive and reproduce, it WILL (because, well, there's no pressure against it), forming sub-species.

Yes I was pondering upon that after posting. If selection by resource pressure is present, however, the species as a whole will become more adapted to its environment much faster. The only remaining question is whether the species needs to be adapted to its environment. If it can survive perfectly in any form, then it will evolve in all sorts of crazy directions. Then again, if there's no pressure, the population will also grow exponentially, leaving the question whether small individual mutations can still effectively cause an entire species to evolve. Kind of like the human race really. There's just too many of us, with too little selection (even the weak can reproduce quite easily). On top of that, our environment is evolving much faster than we ever can biologically. Evolution (at least in the biological sense) requires a relatively stable environment, since it only goes very slow.

 

This is definitely one of my favorite subjects ever since I took an Anthropology course last year. I learned so many things about evolution, it's really changed the way I view life. It's pretty crazy to realise that we're all just a side-effect of a completely coincidental combination of conditions in this tiny part of the universe, which just happened to be so that some molecule managed to replicate and hasn't stopped since. There's so many different ways it could have evolved, but we're now stuck in our current bodies (and behaviors) because those are the ones that proved useful in reproducing in an environment that could only support so much.

[Walsingham]

It's a slighty screwy way of looking at it, but yes I guess that without the environment having a best fit then organisms cannot evolve to suit it.

 

My next line of thinking centres on how finely tuned an organism is to that environment (x). As x changes it may become harder and harder for organism z to fit in. The question then becomes how fast the organism evolves, vs how fast teh environment changes, vs how finely tuned z has to be to the 'value' of x.

 

Subsidiary: DODOS. They existed in an environment without predator pressures.

[Darth InSidious]

"Most of us (except perhaps some Americans with their weird obsession with Creationism)"

 

Bigot criminal.

Wait, I think I know this one.

 

Is the answer "macaroni handbag"? It's "macaroni handbag", isn't it?

[Oblarg]

Any self-replicating system exposed to randomness in its code will evolve.

 

Kind of obvious isn't it? Under the premise of course that the resources required to replicate are too scarce to support an entire generation. Only then can you get a selection, be it natural or not.

 

That's not entirely correct though is it? (Which is actually detailed in the article). It's a common misunderstanding that evolution requires natural selection - it doesn't. If mutation is occurring, and even if there are no resource pressures, then if the mutant can survive and reproduce, it WILL (because, well, there's no pressure against it), forming sub-species.

 

Genetic drift is a fairly well-known phenomenon.

[Walsingham]

Tried to have a discussion about this in teh pub last night. Turned into a discussion about how to entice a gigantic baby penguin to the antarctic

[Moose]

And your conclusion?

[Pope]

It's a common misunderstanding that evolution requires natural selection - it doesn't. If mutation is occurring, and even if there are no resource pressures, then if the mutant can survive and reproduce, it WILL (because, well, there's no pressure against it), forming sub-species.

I thought about this some more. Replication requires energy, no? So even with an abundancy of resources, if the mutant has evolved in a way which disables it to consume the energy required for reproduction, it will not be able to pass along this evolutionary path. It would seem to me that this is just another form of selection.

 

Then again, I'm talking about evolution in the biological sense again. I am genuinely curious what the results would be of a program in which fast-mutating entities (meaning the offspring would differ largely from its parent, as opposed to biological mutation) do not require resources/energy to replicate (e.g. by multiplying on regular intervals).

Edited January 5, 2010 by Pope