Talk:Universal common descent

Recently split from Common descent see also Talk:Common descent

UCD Theory or Hypothesis

In one paragraph in the intro it is called a theory in another it is called a hypothesis...which is it? Pbarnes 22:59, 11 December 2006 (UTC)

Evidence for universal common descent

This section seems like it would be better suited at wikireason. Is there any way to clean this up some? Pbarnes 23:07, 11 December 2006 (UTC)

I edited it some...does it work better for wikipedia? Pbarnes 19:46, 22 December 2006 (UTC)

Genetic Codes and Translation

Alright, I suppose I'd better take it to talk then. While I admit, since I am not a biologist, that there's every possibility my edits were incorrect, I'd like to at least know what was incorrect about them. In one edit, I pointed out that UCD is not an origin of life theory (a point which I think not only is widely acknowledged, but also supported by the linked page). In another edit, I changed the description of the "Genetic Composition" subsection to explain, briefly, the process of translation and how it relates to the phrase "genetic code." I believe, again, that both common knowledge and the linked page agree with my edits, as does the reference given. Strictly speaking, though, the referenced article is not about evidence for UCD from either universality of dna or universality of the genetic code. Insofar as the reference has anything to do with evidence for UCD, it concerns the variations in the genetic code rather than the mere existence of DNA. The evidence alluded to in the reference is really a rather more powerful argument than DNA alone, don't you think? As it stands, it seems to me that the phrase genetic code is being misused and the evidence in that section is far weaker than it could be otherwise (and tagged with an irrelevant reference). Thoughts? TheIncredibleEdibleOompaLoompa 15:22, 1 February 2007 (UTC)

The theory of biological evolution is by definition not a theory of the origin of life because that is covered by chemical evolution from non-life to life. Universal common descent inckudes chemical evolution because horizontal gene transfer means that there was no actual last common ancestor that contained all of the genes ancestral to those shared among the three domains of life. Each contemporary molecule has its own history and traces back to an individual molecule cenancestor during that period of chemical evolution prior to biological evolution. WAS 4.250 16:53, 1 February 2007 (UTC)

While I can see what you're saying here, I generally wouldn't agree that the earliest phase of UCD overlapping with theories of the origins of life causes UCD itself to become a theory on the origin of life. I would say that replacing the phrase origin of life with diversity of life would improve the intro. The information you're talking about probably needs to have its own section explaining how historically, the theory of universal common descent led to the discovery that it was a last universal common gene pool rather than a LUCA. The information is valuable, but I can't see how it justifies declaring the entire theory of universal common descent to suddenly be a theory of the origin of life. TheIncredibleEdibleOompaLoompa 09:11, 3 February 2007 (UTC)

The other change made no sense at all to me and your comments seem to me to indicate one of us is misreading the text. Perhaps if you added text rather than changed text, you could accomplish your goal here? Give that a try? WAS 4.250 16:53, 1 February 2007 (UTC)

I'm not quite sure how to explain this any better, but I'll try. It seems to me that two separate arguments for UCD are being mixed and muddled in that little paragraph. Argument A looks like "all life on earth uses DNA/RNA. This is evidence for universal common descent." Argument B looks like "the genetic code, the mapping of nucleotides to amino acids utilized in the translation of DNA/RNA, is universal. This is evidence for common descent." Both are, in fact, evidence, but I maintain both that the latter argument is stronger and also that the paragraph as it stands now confuses the two, or at least probably serves the purpose of confusing the two in the mind of an average reader. TheIncredibleEdibleOompaLoompa 09:11, 3 February 2007 (UTC)

Looking at the 4 sentences in the paragraph, the first two sentences are appropriate for either argument a or argument b. The fourth sentence and the reference are clearly referring to argument b. The third sentence is a problem, however. It seems to refer to DNA and RNA as "these genetic codes" which is not the usage of the phrase genetic code which is commonly used in argument b, is not the usage that is used in the reference, is not the usage used in the linked Wikipedia article on genetic code, and is not the usage used in the very next sentence. Whoever added it seems to think that genetic code is synonymous with the transmission medium, or perhaps with the genetic sequences themselves. TheIncredibleEdibleOompaLoompa 09:11, 3 February 2007 (UTC)

The very least that can be done to fix the sentence to is change "these genetic codes" to "the genetic code". I did this, but also added a brief description of what the genetic code was, since there's currently no transition between the first two sentences which talk about DNA/RNA and the third sentence which talks about the genetic code. My edits transformed the paragraph into argument b. If there was something inaccurate or confusing about my modification, we should probably fix it here. The other way this could be resolved is by replacing the phrase "genetic code" with "DNA or RNA" somehow, removing the last sentence and removing the reference. This would be the beginning of transforming the paragraph into argument a instead.. TheIncredibleEdibleOompaLoompa 09:11, 3 February 2007 (UTC)

You understand my points. I agree with your points. How about if you edit the article to reflect the above in as clear and verbose (in a good way) way as you did above? WAS 4.250 20:02, 3 February 2007 (UTC)