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How can anyone make this claim? Is there a single example of a living organisms that is not DNA based? If everyone organism alive today uses DNA then it is reasonable to assume that the LUCA was DNA based (which does NOT preclude the possibility that life started off as RNA based). I guess that's wikipedia for you.
Quote from article "Note, however, that some studies suggest that LUCA may have lacked DNA and been defined wholly through RNA". How can anyone make this claim? Is there a single example of a living organisms that is not DNA based? If everyone organism alive today uses DNA then it is reasonable to assume that the LUCA was DNA based (which does NOT preclude the possibility that life started off as RNA based). I guess…
Why is there only one "beginning of life" on earth? If life is likely to form in earth-like conditions after a few billion years, shouldn't there be more than one "last universal ancestor"? Does this suggest that life on other earth-like planets may be very rare, or that ours is a unique life form for our environment?
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC148579/
That is, DNA evolved twice on Earth. That seems like "life beginning more than once" or something very close.
Note that almost everyone involved thinks that mitochondria and chloroplasts are prokaryotes captured one way or another by Eukaryotes, so the distinction about two evolutions of DNA gets a bit messy.
For anyone wondering if there were multiple LUAs: https://www.reddit.com/r/askscience/comments/1bjvxs/how_do_w...
Doesn't the existence of multiple LUAs contradict either the word 'last' or the word 'universal'?
Quote from article "Note, however, that some studies suggest that LUCA may have lacked DNA and been defined wholly through RNA". How can anyone make this claim? Is there a single example of a living organisms that is not DNA based? If everyone organism alive today uses DNA then it is reasonable to assume that the LUCA was DNA based (which does NOT preclude the possibility that life started off as RNA based). I guess…
Consider that cells are mostly ribosomal RNA/units by mass.
Why is there only one "beginning of life" on earth? If life is likely to form in earth-like conditions after a few billion years, shouldn't there be more than one "last universal ancestor"? Does this suggest that life on other earth-like planets may be very rare, or that ours is a unique life form for our environment?
It's very possible that life arose independently multiple times, but one group grew fast enough to drive all the others to extinction. The life forms we observe now almost certainly came from one ancestor due to the numerous molecular similarities (e.g. use of the same form of DNA).
The parallel that comes to mind is the mitochondria within animal cells, they probably originated as independent bacteria.
Quote from article "Note, however, that some studies suggest that LUCA may have lacked DNA and been defined wholly through RNA". How can anyone make this claim? Is there a single example of a living organisms that is not DNA based? If everyone organism alive today uses DNA then it is reasonable to assume that the LUCA was DNA based (which does NOT preclude the possibility that life started off as RNA based). I guess…
Fortunately, a citation is provided. I guess that's wikipedia for you.
These are from the New Scientist article that wikipedia referenced. I don't understand the references here, but hopefully someone will see this that can help explain exactly how an organism doesn't have DNA, only RNA.
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[0]: http://www.biomedcentral.com/1471-2148/10/383
[1]: http://www.newscientist.com/article/mg21128251.300-first-lif...
Earlier quoted context omitted.
Doesn't the existence of multiple LUAs contradict either the word 'last' or the word 'universal'?
The possibility of 2 non-monozygotic twins having identical genes is not zero, just astronomically low. Its the same for LUA.