The origin of life?

[Hume's Ghost]

I wonder if you sceptics could help me on a point which puzzles me.

I accept Darwin and the theory of evolution by means of natural selection. I am also an atheist and do not accept "intelligent design". (And I am not a scientist but a philosophy student.)

But...

...whilst Darwin's theory explains how life, once it existed, evolved in the forms it did, I do not think it explains how life began at all.

At one point, this planet was barren of life, like all the other planets we know. Then at the next point, it had life. How did "lifelessness" evolve into "lifefulness"?

[Admin]

The thinking goes along the lines of...

When systems are driven far from equilibrium (such as chemical reactions being driven by heat in the Earth's early days or at thermal vents on the ocean floor) they have a tendency to 'self organise'. You often get some quite complex outcomes from very simple starting conditions.

If a lot of complex molecules were being formed it would only require some of them to be able to 'replicate' (i.e. influence more copies of themselves) for Darwinian selection to occur thus leading to more complexity as those molecules best able to copy themselves thrived at the expense of others.

So as with many arguments from complexity, if you break it down into small steps each step is not particularly unlikely even though the end result may look that way.

There are undoubtedly other theories but the basic premise is that before life (however you define it) emerged, some system of self-replicating molecules was there first to give rise to the Darwinian selection process.

[Hume's Ghost]

Thanks John. This is very helpful.

Would those self-replicating molecules had to have been present since the creation of Earth? If not, how did or could they arise?

And is this explanation within what is usually understood to be Darwinism or is this a different matter (excuse the pun!)?

[Mongrel]

But...

...whilst Darwin's theory explains how life, once it existed, evolved in the forms it did, I do not think it explains how life began at all.

At one point, this planet was barren of life, like all the other planets we know. Then at the next point, it had life. How did "lifelessness" evolve into "lifefulness"?

To be fair Evolution only explains what happens once life is started, what you're looking for is Abiogenesis

[Hume's Ghost]

Thank you so much for this incredibly helpful post.

For me, it is a "missing link". My one reservation with Darwinism (as I understood it) has always been that it explained only what happened once life was about, not how life itself was created.

That is why I have never seen it as contradicting (totally) the Woos who believe in divine origin.

Again, many thanks.

[filippo lippi]

If you accept that evolution is a gradual process why do you think that non-life to life should happen in a flash?

[Hume's Ghost]

If you accept that evolution is a gradual process why do you think that non-life to life should happen in a flash?

Good point.

If at point [x] it is clear that, by any sensible definition, there was not life, and at point [z], by the same definiton, there was life, that interim period [y] is very interesting.

I wonder if there is a strict definiton of life which would make period [y] fairly short? Non-life one second, life the next..!

[Mongrel]

For me, it is a "missing link". My one reservation with Darwinism (as I understood it) has always been that it explained only what happened once life was about, not how life itself was created.

That is why I have never seen it as contradicting (totally) the Woos who believe in divine origin.

Again, many thanks.

As a point of order, "Darwinism" is a 150 year old theory which has been expanded and built upon in the intervening years to become Evolutionary Theory. As a word Darwinism is used almost exclusively by creationists and cdesign proponents.

[vbloke]

I wonder if you sceptics could help me on a point which puzzles me.Hmm.


I accept Darwin and the theory of evolution by means of natural selection. I am also an atheist and do not accept "intelligent design". (And I am not a scientist but a philosophy student.)Why not just say "I support evolution"?. It's an odd way to phrase a question.


...whilst Darwin's theory explains how life, once it existed, evolved in the forms it did, I do not think it explains how life began at all.It's not supposed to. It never tries to. Only evolution deniers think it does.


At one point, this planet was barren of life, like all the other planets we know. Then at the next point, it had life. How did "lifelessness" evolve into "lifefulness"?It didn't. Evolution does not concern the origins of life, it only concerns itself with what happens once life is there.

Once again, I question your motives for asking, especially in light of the way you've worded the question.

[Hume's Ghost]

This is the second time you have questioned my motivation. It is a serious question to raise. You clearly suspect I have an ulterior motive. I think the following points should settle the matter.

1. As I said earlier in the thread, I am an atheist. Not just "agnostic"; I disbelieve in any god. I thought by saying that clearly, I would remove any suggestion that I was a "sock" for religious sorts. It would appear that this is not enough.

2. I am also not a scientist. I am, amongst other things, a student of philosophy. I do not pretend to understand science as well as scientists. That is why I said "accept" - I do not pretend to fully understand. However, by "accept" I wanted it to be clear that I was also not a "sock" for ID. Again, this was not enough for you.

3. I actually had a genuine query and a gap in my own understanding. Again, I am simply not a scientist. That is why I asked. I was happy with the response and now feel I have a far better grasp of how life developed from nothing.

4. But, in any case, why should my motives even matter? I set out a query which was promptly answered. Why should this (rather agreeable!) sequence of acts be any different because of an ulterior motive?

5. Even if I had an ulterior motive (which I do not believe I have) the best way to deal with it is to surely deal with the statements and arguments I set out. I feel as if I am being accused of "thoughtcrime", not being pure of intent enough not to be a proper sceptic!

Perhaps you should ease up a little in questioning my motives? (There is no need for you to apologise, of course, as I am not offended.)

[Gilbs]

talkorigins.org/faqs/abioprob/abioprob

This may help. Although quite technical.

I also only recently came to have a better understanding of the distinction between Evolutionary theory and the origin of life itself. Although I am sure there are evolutionary processes involved in abiogensis; perhaps other people on the forum could help us out here?

Thats why it is quite amusing when you hear creationists debate; as very often their argument for ID and dismissal of darwinism (deliberate use of the word since the theory as of 150 years ago is how they choose to understand it to justify their worldview) is based on the statistical improbability of life starting naturally when evolutionary theory, as has already been stated, is about what happens after life started.

This article deals with the probability issue as well.O0

[Mongrel]

I also only recently came to have a better understanding of the distinction between Evolutionary theory and the origin of life itself. Although I am sure there are evolutionary processes involved in abiogensis; perhaps other people on the forum could help us out here?

I'm not a Evo Biologist so I'm happy to be corrected...

My limited understanding is that, simplistically, once the bunch of cells become capable of replication through RNA (I think RNA was first), that's when evolutionary theory takes over. With the replication comes minor errors, mutations, the majority are neutral (useless) or disadvantageous, a small percentage are advantageous and allow the cells to eat better\use energy more efficiently\detect food better\move a bit quicker\breed faster etc. These cells can then grow 'bigger and stronger" or just faster thus evolving.

[British Sceptic]

if you watch Bronowski's 'the ascent of man' all shall be explained.

regards,

Den.;)

[bobdezon]

Yes, you must watch. All will be explained in great and intricate detail.

http://uk.youtube.com/watch?v=BS5vid4GkEY&feature=PlayList&p=AC3481305829426D&index=0&playnext=1

[brianp]

My limited understanding is that, simplistically, once the bunch of cells become capable of replication through RNA (I think RNA was first), that's when evolutionary theory takes over. With the replication comes minor errors, mutations, the majority are neutral (useless) or disadvantageous, a small percentage are advantageous and allow the cells to eat better\use energy more efficiently\detect food better\move a bit quicker\breed faster etc. These cells can then grow 'bigger and stronger" or just faster thus evolving.
And some mutations which are neutral or even slightly disadvantageous under current conditions can also get passed on and may, millions of years later, prove advantageous as conditions change. This allows a species, or a subset of the species (ie those carrying those mutations), to quickly adapt to a change of climate or to better fight a new disease.

[Cuddles]

My limited understanding is that, simplistically, once the bunch of cells become capable of replication through RNA (I think RNA was first), that's when evolutionary theory takes over.

Well, sort of. It's much more likely that RNA came first and cells only appeared much later. When life first appeared it would have been a single molecule, complex things like structure and protective coatings would have required an awful lot of time before they evolved. I think this is where many people have a problem with abiogenesis - they imagine that cells must have appeared fully formed, and realise how incredibly unlikely that is. And it is. But single molecules, even extremely complex ones, are orders of magnitude more likely to occur than even the simplest structures.


And some mutations which are neutral or even slightly disadvantageous under current conditions can also get passed on and may, millions of years later, prove advantageous as conditions change.

This is a very important point that I've never seen explained properly anywhere other than Science of Discworld 3 (I think, might have been 2). Natural seclection does not work on new mutations. Natural selection is a statistical process that requires large numbers of organisms. A 1% better chance of surviving means nothing if you are the only one with the improvement, but if there are millions of you with it, that chance represents a significant improvement over the whole population.

I think this is another common misunderstanding of evolution. People tend to imagine that a mutation occurs, immediately gives the host a big advantage and goes on to spread throughout the gene pool and take over the world. Which all seems very unlikely and should be drowned out by chance events. And that is exactly what happens. Except possibly in some very unsual cases, the benefit of any new mutation will be massively outweighed by variation in the rest of the environment. It is only after a mutation has spread to a significant number of organisms that statistical processes can go to work on it, which means not that some mutations will be passed on for millions of years regardless of benefit, all mutations currently being selected for will be millions of years old.

[Mongrel]

Thanks for the clarifications :smiley: