Carbon 14 age dating
His goal was to find sections of dead trees whose rings could be pieced together to extend the samples as far back in time as possible.He found an irregular slab from a bristlecone pine that spanned the years 3050 BCE to 2700 BCE.
This rules out carbon dating for most aquatic organisms, because they often obtain at least some of their carbon from dissolved carbonate rock.
So the rate at which this happens, so the rate of carbon-14 decay, is essentially half disappears, half gone, in roughly 5,730 years. Even better, maybe you dig a little deeper, and you find another bone. And you say, wow, you know this thing right over here has 1/4 the carbon-14 that I would expect to find in something living. Well, if it only has 1/4 the carbon-14 it must have gone through two half lives.
After one half life, it would have had 1/2 the carbon.
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.