[Ax]

I’m not the smartest guy in the room. I had one Anthropolgy 101 course and Geology 101/102 in college MANY years ago, and nobody ever explained to me how radio carbon dating can pinpoint a date to within 500 years 40,000 years ago. Can anyone explain it to me?

[struggle]

You can’t...after 4,000 years the returns become very random.

[JimSEA]

I can’t improve on Wiki’s opening sentence: Radiometric dating (often called radioactive dating) is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.[1]. It is way beyond C14 today and is constantly refined and expanded.

[Pollster1]

Carbon dating is considered useful out to about 60,000 years. I have my doubts on the accuracy this long ago because of uncertainty over the isotope distributions long ago, but the method is recognized as appropriate for dates in that range.

[Torquay]

I know a few things about all of this!

[SunkenCiv]

There’s a range of error that increases based on the remaining quantity of C14. There’s been an improvement in the detection and measurement such that the limit has increased from about 45K to about 60K and the range of error has improved. A 500 year range for 40K years is 1.25 percent.

[Steve Van Doorn]

A quote from wikipida (in this case isn't bad):
"Plants take up atmospheric carbon dioxide by photosynthesis, and are ingested by animals, so every living thing is constantly exchanging carbon-14 with its environment as long as it lives. Once it dies, however, this exchange stops, and the amount of carbon-14 gradually decreases through radioactive beta decay with a half-life of 5,730 ± 40 years"

If they decay is over 10 half-life's of the radioactive substance it becomes guess work when the half life started if you take into account all other natural variables acting on the subject. With CO-14 that is anything over 60,000 years it becomes questionable.