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?

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    $\begingroup$ 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. $\endgroup$ – fileunderwater May 20 '15 at 12:50
  • $\begingroup$ I agree with @fileunderwater. Perhaps the following questions may help you to specify this question into something that can be realistically answered: biology.stackexchange.com/questions/22008/… and biology.stackexchange.com/questions/1663/… $\endgroup$ – AliceD May 20 '15 at 12:53
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    $\begingroup$ @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. $\endgroup$ – fileunderwater May 20 '15 at 13:10
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    $\begingroup$ Related: Can scientists create totally synthetic life?, How did the first self replicating organism come into existence?, and probably others under the abiogenesis tag. $\endgroup$ – fileunderwater May 20 '15 at 13:12
  • $\begingroup$ 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. $\endgroup$ – Yehosef May 20 '15 at 21:08

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.

  • $\begingroup$ 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? $\endgroup$ – Yehosef May 20 '15 at 22:47
  • $\begingroup$ 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. $\endgroup$ – Jack Aidley May 21 '15 at 9:48

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