Originally posted by Phydeaux
Well... In this book I have some,
There are some more on that page but I don't have time to right them, and this, more from the book,
I know. There always is the problems of
- lab contamination (i.e. not the artifact is actually dated, but something else that got stuck to it in the lab, or a mixture)
- field contamination (same as above, but before the object reaches the lab)
- intentional 'mistakes' - speaks for itself
- erranoeus field data (the supposedly older object is mixed up with a different one - what a surprise it is younger!)
- taphonomical contamination (i.e. animals digging or so get older/younger charcoal or whatever attached to the object
- broken machines (giving false readings)
- calculation errors (how easy is it to read a handwritten, smeared 2 for a 3 or vice versa, now if that is a 10 to the power of 3 instead ofa 10 to the power of 2, that makes a huge difference.
- errors to do with 'association'
Now, the last one accounts for most of the conflicting data, so I will explain it:
It used to be you needed several grams to date C-14. Many objects (seeds) didn't bring that much. Others couldn't be sampled - imagine cutting a piece that weighs several grams out of a 180 gram bone fragment

So, what to date? Well, charcoal from the same level! That often is abundant!
Where the problem here? The charcoal may be significantly older or younger

Now, if you can (as we can toady) date with a lot less matter, you cna date the actual object. no surprise you will sometimes find dates to vary!
As for the two examples you quote:
the first is an example of surface contamination I would think. They wouldn't bore holes into an old artefact, what they'd do is take tiny snips fromthe surface - and depending where you take them, what touched the artefact in that place etc you will get varying results. Also, maybe the thing was repaired after it had been sitting around for a few centuries?
The huge ages from the European institutes are probably simply errors in thedating process. But by now the method has been used so much that most erros have been found out.
the second example:
the mammal bones obviously do not belong into the rocks! how they got depoited there I have no idea, but AFAIK most of the Lewaky finds were surface finds - prone to have younger bones lying around.