Dating of fossils by scientists
Levels of carbon-14 become difficult to measure and compare after about 50,000 years (between 8 and 9 half lives; where 1% of the original carbon-14 would remain undecayed).
The question should be whether or not carbon-14 can be used to date any artifacts at all? There are a few categories of artifacts that can be dated using carbon-14; however, they cannot be more 50,000 years old.
When scientists first began to compare carbon dating data to data from tree rings, they found carbon dating provided "too-young" estimates of artifact age.
Scientists now realize that production of carbon-14 has not been constant over the years, but has changed as the radiation from the sun has fluctuated.
For example, if they believed it would take 200 million years for an ammonite (somehow) to turn gradually into say a dog, then all rocks containing fossil ammonites (the “index fossil”) would be given an “age” 200 million years older than rocks containing fossils of dogs: “…
Carbon dating cannot be used on most fossils, not only because they are almost always allegedly too old, but also because they rarely contain the original carbon of the organism that has been fossilized.
Also, many fossils are contaminated with carbon from the environment during collection or preservation procedures.
As stated previously, carbon dating cannot be used on artifacts over about 50,000 years old.
These artifacts have gone through many carbon-14 half-lives, and the amount of carbon-14 remaining in them is miniscule and very difficult to detect.