So should we find useless proteins in our bodies? Or is DNA so precise that there are none? I suppose that natural selection may have ruled out the DNA that gave instructions for useless proteins.
There's lots of useless stuff clunking around in our bodies. From bunches of "junk dna" which codes for nothing (that we know of), to redundant coding where more than one gene does the exact same thing.
And at a macro level - look at the appendix, the ticking timebomb of useless left over body parts. It's like it's there just to need to be removed.
As for natural selection ruling out the DNA which codes for useless proteins - natural selection is very good at selecting for something beneficial or against something harmful, but it's not very good at weeding out something which is neutral.
If you have a bit of junk DNA which has no real effect on your ability to reproduce (either for or against), chances are natural selection is gonna let that one slip on by.
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