Wrong,
They are not C-14 dead.
So test all things supposedly over 6000 years old.
And the long dating of things has been proven false with the great errors in dating things that are known historical events.
With *any* dating method, you need to understand how it works and why it works. That will mean you will also understand when it *doesn't* work.
With C14 dating, there are several things that need to be understood to use it correctly.
1. Living things usually get their carbon from the atmosphere, eventually. So, animals eat plants and those plants get their carbon from the atmosphere.
This means that for most living things, their concentration of C14 is the same as that of the atmosphere.
Are their exceptions? YES. Some deep sea shell fish get the carbon in their shells from carbonate rocks and not from the atmosphere.
2. When a living thing dies, it stops interchanging carbon with the atmosphere. After that, the C14 in their bodies decays.
This means that the date when that living thing died can be determined by the amount of C14 in their bodies compared to that in the atmosphere.
But this means that the C14 in those clams has *already decayed* and so will NOT give a correct date for those clams.
3. C14 is produced in the upper atmosphere when nitrogen atoms are hit by neutrons. This same basic process happens during atmospheric nuclear tests.
This is why anything younger than the 1950's won't give good dates via C14. The amount of C14 in the atmosphere has changed in a way that invalidates the method for such.
Are there other ways C14 can be made? YES. if there are nitrogen atoms in a radioactive rock that emits neutrons, there can be C14 made in that rock. This can give a larger amount of C14 than would be expected otherwise. NOTE: this would give an artificially *young* date. The real date would be older. This also means there is a very small amount of C14 that is present whenever a formerly living thing is near to radioactivity. This causes problems by giving a date that is too *young*.
4. The rate of production of C14 in the atmosphere changes over time.
This is a serious issue. it means that the amount of C14 in the atmosphere today is not the same as in the past, so things that died in the past started out with a different amount of C14 in their bodies. To get good dates means we have to take that into consideration.
This is why there are 'raw' C14 dates and 'calibrated' C14 dates. The calibrated dates have been cross referenced with items we know the ages of by some other method. This allows us to compute the amount of C14 in the atmosphere in the past and thereby use C14 for other things.
This is also why C14 dates can have fairly larger 'error bars', especially for certain time periods when the original C14 production was different.
Other dating methods do not have this issue, by the way.
5. Our instruments measuring the amount of C14 in a sample *today* are not perfectly accurate.
In essence, we try to determine the amount of C14 right now and the methods have some amount of (expected) error. The effect is that if the amount of C14 is high, the *percentage* error in the measurement is small. But if the actual amount is small enough, the *percentage* error can be high.
The effect of this is twofold:
A. the error bars for computed dates in younger samples will be smaller than for older one.
B. If the actual amount of C14 today is too small, we lose all ability to determine how much we really have (by the usual methods). This means that for small amounts of current C14, the method is useless.
in practice, this is why anything over about 50,000 years old cannot be dated by C14 with any reliability.
6. Contamination by modern C14 (in the atmosphere, on fingers, etc) is a real problem, especially for older samples.
An incompetent or a person that is not careful enough handling the samples can mean the dates produced are off (usually too young).
So, to use the method *correctly* means understanding these parameters.
So, if you want to claim the method is unreliable, you need to *first* give an example where it is used *correctly* (take into consideration all of the facts above) and *still* manages to give a date that is faulty.
And, by the way, other methods of radioactive dating do not have many of these issues. For example, uranium is NOT produced in the atmosphere, has a longer half life (meaning amounts today are easily measured), are not dependent on living things, etc.