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The current idea is that all life evolved from a single cell. Analysis indicates the probability of two different origins being very unlikely, given shared DNA. However, why couldn't numerous organisms have evolved and then conjugated, with a few lineages surviving? It would vastly increase the odds of modern organisms sharing the DNA that they do.

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Because they would not use the same DNA codons. Codons are extremely conserved across life, with only minor variations, there is no reason this should be the case unless those codons are inherited from a common ancestor. This is contingent on what you mean by organism, prior to the incorporation of ribosomes it would be more possible.

If what you suggest had occurred it would drastically DECREASE the odds modern organism would share the same DNA.

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  • $\begingroup$ How many different collections of codons would be useful for encoding genetic information in an environment in which life evolved? $\endgroup$ – Daniel Goldman Sep 23 '18 at 0:27
  • $\begingroup$ Another thought: if different systems of codons existed in different lineages, wouldn't that decrease the probability of conjugation so that if any cells did go through early conjugation, they were likely with similar codon systems? $\endgroup$ – Daniel Goldman Sep 23 '18 at 0:34
  • $\begingroup$ they would have to have identical codons to fuse, the likelihood of separate lineages ending up with identical codons is close to nil. multiple codon lineages could and likely did existed but only one of the contributed to existing life. $\endgroup$ – John Sep 23 '18 at 2:14
  • $\begingroup$ Could you provide some data to that effect? Again, how many different systems of codons function reasonably well in the environment in which abiogenesis likely occurred? $\endgroup$ – Daniel Goldman Sep 23 '18 at 12:03
  • $\begingroup$ Also, are you talking about the codons or the nucleotides themselves? $\endgroup$ – Daniel Goldman Sep 23 '18 at 12:04

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