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Evolution of Living Cells from Non-living Organic Matter


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#1 Crulo

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Posted 14 December 2013 - 12:31 AM

Can anyone point me to some material pertaining to the topic of why we don't still see new living cells forming from non living matter? Or to material that shows we do see new cells forming? Are new species (bacterial, single cell organisms) that we find always just evolved from other ones in this day and age? I find it hard to believe that we can't point to something in nature and say "look, new cells trying to form!" Whether they be successful processes or failed ones. Shouldn't whatever processes that lead to cells being formed still be going on? Again, whether they lead to actual living cells or just failed blobs of organic compounds.

 

Were the conditions on the earth in the past, the environment, just so different and allowed for living cells to form and these certain conditions no longer exist? Is the current environment so different that these processes no longer happen?

 

If we all evolved from the same single cell organisms...I am just wondering if we have any good explanations as to why the process is so hidden from us. Do we just not know where to look at this moment in time? Unless the process relied on early earth conditions...shouldn't we be able to see these processes still trying to happen?

 

I am not challenging evolution...or other theories... this is just an honest question that I ask my self anytime I start thinking about early life forming on earth.

 

I imagine the first cells didn't have DNA/RNA also... is there any information out there that explains how the first cells might have formed DNA (RNA)? Did one particular group of living cells form DNA or did various cells all evolve DNA from their own separate/different processes? Then, if we find life on other planets is there a chance they would have DNA...just maybe with a different sugar? I ask this because if the first living cells on earth formed by some process...and all living organisms on earth now have DNA/RNA... is it wrong to think that that must be the only viable path for life? Do cells form from various processes and all develop RNA/DNA independently... or did a specific group of cells that formed get lucky and evolve DNA and all the other types of cells failed and we just don't see those organisms any more?

 

I'm just looking for something to read...doing some Google searches for this didn't really get me any where...so if any one out there has any material they think would help me with some of these questions please point me in that direction!

Thanks in advance :)



#2 bob1

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Posted 14 December 2013 - 01:16 AM

Short answer - new cells very very small, earth relatively very very big and mostly unexplored (oceans anyone?).

 

Long answer - the conditions have changed significantly since the first life that we can identify - approx 2 billion years ago (2,000,000,000 years), earth's age is about 4-4.5 billion, the first cells probably started to form sometime after liquid water could exist on the surface, but no-one knows how for sure.  It is highly likely that the right mix of chemicals and and temperatures etc. no longer exist in most places, though there may be good conditions around things like black smokers.  However, in all the environments so far explored, life already exists - which would probably be able to more efficiently use the resources available, and hence out-compete any new life forms.

 

Check out the RNA world hypothesis.



#3 Crulo

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Posted 14 December 2013 - 01:28 AM

Current life out competing new life is something I had considered, didn't come to mind when making the post.

 

I'll check out the RNA hypothesis.

 

Thanks for the reply.



#4 hobglobin

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Posted 14 December 2013 - 04:52 AM

I'd agree with bob1's idea that such life-forms are or would be mostly out-competed by our existing life since especially bacteria and archaea occur more or less everywhere (even at extreme locations such as the black smokers) and would surely digest such early life forms as good energy source. Another obstacle would be oxygen which is reactive enough to oxidise unprotected macromolecules.

Therefore the locations  with these conditions are rare: anaerobic, sterile, sufficient organic and inorganic molecules (water, carbon dioxide, ammonia, methane, hydrogen sulfide, etc), enough reaction energy, perhaps special minerals as catalysts (that's what the conditions on the early environments were supposed to be) . In the young earth it is supposed that UV light was a good energy source, but today it would be impossible as it's only available in or near the oxygen atmosphere.

But in hidden places such as poriferous stones or rocks near an energy source such as a black smoker, why not? Anyway the chance that all of the conditions are fulfilled seems tiny and the process would need a very long and more or less undisturbed time (one idea would be that it's occurring there frequently but always disturbed and destroyed by adverse conditions/bacteria already in an early stage). I guess in places like Europa it's similar or more likely.

 

And another artificial DNA type is XNA, a keyword for searching is abiogenesis.

 

And finally for the black smokers this is a good read: W. Martin and M.J. Russell (2003), On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleared cells. Philos. Trans. R. Soc. London Ser. Bd. 358 (1429): 59–85.


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