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Is the minimum criterion for life a single cell? It seems that self-replicating RNA is not enough, but I don't know.

What would be the most basic cell that could fit this criterion and what cells today would be most similar?

terdon
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Yehosef
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    Even though it is short, this question is really broad. To answer this you need to get into the definition of life (e.g. the line between "protocells" and cells) and minimum definitions of a biological cell. Also note that you can have evolution in the absence of life, see e.g. Evolutionary computation - all that is needed is variation, selection, heritability and reproduction. – fileunderwater May 20 '15 at 12:50
  • I agree with @fileunderwater. Perhaps the following questions may help you to specify this question into something that can be realistically answered: http://biology.stackexchange.com/questions/22008/simplest-biological-organism/22009#22009 and http://biology.stackexchange.com/questions/1663/are-cells-really-the-basic-unit-of-all-life/1666#1666 – AliceD May 20 '15 at 12:53
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    @AliceD I agree that it should be refined, and parts of the question is probably a close duplicate to the first Q you linked. For the second question, is also unclear whether the comparison should be against the origin of life (~LUCA) or basic cells that can live under current environmental conditions - the external conditions have changed quite a bit. – fileunderwater May 20 '15 at 13:10
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    Related: Can scientists create totally synthetic life?, How did the first self replicating organism come into existence?, and probably others under the [tag:abiogenesis] tag. – fileunderwater May 20 '15 at 13:12
  • Thanks for the comments everyone! I didn't realize the line was so fuzzy. I guess I never would have thought of self-replicating RNA as life but it seems that are people that define it that way. – Yehosef May 20 '15 at 21:08
  • Why is this too broad? - there is a process called abiogenesis and there is a process called evolution. I assumed the line is clear, perhaps the answer is that's it fuzzy as the answer below discussed and I commented. It could be that the answer is relative based on the definition of "life", but that itself could be the answer. – Yehosef May 21 '15 at 11:17
  • Yehosef, one problem is that your question is essentialistic/semantic. The way you've phrased it suggests that there is an inherent importance to the words "abiogenesis" and "evolution", when in science, the words are just tools used to communicate ideas. There is no fundamental answer because it all depends on how you choose to define those terms. In science we use operational definitions for things, and the facts are empirical, stemming from measurements. This question is like saying "what is life", where the answer is "it's a word with a somewhat arbitrary definition", if you follow. – Trixie Wolf May 22 '15 at 19:30
  • @TrixieWolf - I understand better what the with issues with the question are and how I might phrase it differently to get the answers I'm looking for. What now? I could delete the question, but I think the discussion here is valuable because others may have the same question. I guess I'll leave it and the powers that be can close it or do whatever they want. – Yehosef May 24 '15 at 21:30
  • @Yehosef You can just leave the question as it is. Since the question has an upvoted answer it cannot be deleted by you, and, as you say, the discussion can useful for later visitors. – fileunderwater May 27 '15 at 07:16

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I think it's a mistake to assume that there is such a point. All plausible seeming models of abiogenesis currently under consideration involve evolutionary processes long before they reach the stage we'd consider alive.

Evolution will occur whenever there is (a) replication-with-error and (b) selection (simplifying slightly). This is the case with a self-replicating RNA. It is replicating, but those replicates can be imperfect. Imperfections in replication that improve its ability to replicate will be favoured. That's evolution.

Jack Aidley
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  • thanks for the clarification. It seems abiogenesis will go from raw elements until self-replicating molecules and then will combine with evolutionary-type processes until there is "life"(which I'm assuming is at least some self-contained cell) at which point abiogenesis is "done". Is that the right track? – Yehosef May 20 '15 at 22:47
  • Yeah, that's it. Although even then I'd be wary of assuming that there is a single clear line dividing life from non-life, so the exact end point of abiogenesis will be ill-defined. – Jack Aidley May 21 '15 at 09:48