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The simple fact that all known organisms share a common genetic code is powerful evidence that they all descended from a common ancestor.

Life didn't have to have that particular code. There may be others which work equally well (although without examples, this is merely speculation). Once again the only creationist explanation for the unity of the genetic code is "God's whim". It makes sense to have the same genetic code if all modern organisms are descended from the same self-replicator. It does not make sense to use the same genetic code if an infinitely powerful Creator formed different organisms to suit different environments. Unless, of course, you propose limits to the abilities of said Creator.

All organisms - all of them - use left-handed proteins, despite the fact that right-handed proteins exist and are just as good as their left-handed counterparts (in theory, that is - again. Because they don't occur in living organisms we have never observed whether this is the case in living organisms). Common descent, and therefore evolution, is the only concievable reason that all living organisms, from the lowliest yeast to the most lofty eagle, use left-handed proteins. The only alternative explanation is "God's whim", with no further explanation required or desired. Evolution provides the explanation.

Furthermore, all known organisms use the same subset of twenty two out of the 390 naturally occuring amino acids. Again, there is explanation for this fact other than common descent and "God's whim".

It is remarkable that organisms which are so unlike each other - yeasts and birds of prey, extremophilic archaea and human beings - are really so amazingly similar on a molecular level. Creationists and Intelligent Design proponents harp on about the economy of the creation/design process, but as I said before, this places limitations on what is supposed to be an infinitely powerful God. When you have infinite power and infinite ability, there is no reason whatsoever to be economical in your designs. I would suggest that such an infinitely powerful being would not even consider economy when performing such creations.

Common descent, and therefore evolution, is the only reasonable explanation for the astoundingly similar molecular structure of all life on this planet.