graceadieu
Posts: 1518
Joined: 3/20/2008 From: Maryland Status: offline
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quote:
ORIGINAL: vincentML I agree with you egern. I tried to make this point earlier. DNA has just gotta be DNA. There is no reason to think it did not develop many times in different locals of the early hospitable earth and that many of the combinations wet awry. The odds (of reason) favor multiple beginnings before the present form was successful. Self-replicating RNA (genetic material simpler than DNA) will spontaneously form from organic molecules in the right conditions, so it seems likely to me that there was a lot of different proto-life stuff going on in the early oceans before the development of functional cells. And then... where's the line between life and non-life? Is free-floating genetic material "alive" if it can reproduce? Or is it not alive until it's a cell? It does, from what I recall (sorry, former bio major here, but that was almost 10 years ago) look like all cellular organisms are descended from a common ancestor. But there's a staggering amount of diversity among primitive single-celled organisms, too. Also: it looks like a lot of those primitive organisms can just swap genes around between unrelated species or even incorporate stuff from their environment. That makes it hard to classify them or create evolutionary lineages, since species end up sharing DNA or RNA with species that are only distantly related to them.
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