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Originally Posted by mo42
Much of the protein does require specific amino acids, while some sections may be more flexible, this is true. However, assuming that only 5 amino acids are required specifically and that 20 of them can only be one of two amino acids (which is making it significantly more probable than is actually the case), only one of (20^5 * 10^20 = ) 3.2 x 10^26 proteins will give the correct effect, still a far larger number of proteins than could be reasonably expected to be synthesized in the lifetime of the earth.
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Some basic guidelines are that like R groups can be substituted for like R groups. Acid for acid, alkaline for alkaline, polar for polar, non-polar for non-polar. Even in very highly specific sections of the sequence (like the bit that actually makes up the active site), the protein may still exhibit the desired enzymatic function (though not necessarily under the same conditions or at the same reaction rates as the
correct sequence) despite substitutions.
In any event, cells don't search sequence space by randomly dehydrating amino acids and seeing if the folded result does anything useful. Slight mutations alter the function of existing proteins, resulting in families of proteins with similar sequences (though not always similar functions). So you might say that some very specific activity is very rare... but the sequence that we find in living things is very similar to another protein with a generalized function. So we get the majority of the correct sequence through incrememental improvement in a different protein. And then the change from this final optimized sequence (for a different function) is only a small step from this other very specific function which appeared to be improbable.
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Originally Posted by Bauh4us
I remain unconvinced.
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Carbon dating tops out at around 50K years ago. It's not that it becomes increasingly inaccurate past 50K (though it does get less accurate the older you go), but just that, analytically speaking, a sample that was "millions of years old" would be indistinguishable from one that was 60K. So the story is flawed on its facts... no lab would carbon date something at millions of years.
The
TalkOrigins List of Creationist Claims contains a bunch of carbon dating stuff in the CD section.