How does Carbon Dating work? As well as general forensic archaeology!

Question

Not entirely sure if this falls under the Biology or Chemistry tag but heigh ho!

I am a Viking Reenactor and our group is very education focused and as part of my stall on Viking Funerals I talk about how scientists can test bodies to find out where they’re from and what their diets were like but I don’t actually know “how” this works…

In: Biology

Answer 1

To add a bit more precision to what other said. Radiation from space hit the atmosphere of earth and create Carbon 14, while most of the carbon in the atmosphere is carbon 12. Plants use that CO2 to build their body (herbivore eat plant and carnivore eat herbivore) and so you find the same ratio of Carbon 14 to Carbon 12 in the atoms of the body of any living being as you would find in the atmosphere.

Over long period of time, the Carbon 14 in the atmosphere keep getting replenish (that said the exact amount will vary throughout history), but once a living being die it no longer add new carbon to their body. The amount of carbon 12 remain the same because it is stable, but carbon 14 slowly decrease in number as it radiate away.

Knowing how fast carbon 14 decay and by measuring the current ratio of carbon 14 to carbon 12, we can calculate how long it took since the decay started, aka how long since that living being died.

This only work for organic material up to about 50-60,000 years. The reason is that carbon 14 have an half life of 5,730 years. Meaning that after 50-60 thousand years, the amount of carbon 14 decrease by half 8 to 10 times. The amount left is so small by that point that the measurement become meaningless and can’t be relied upon.

Another important aspect is that the amount of Carbon 14 in the atmosphere wasn’t always the same throughout history. A calibration need to be done to adjust the amount of time to represent more accurately the real number. Usually when people publish that kind of data, they give both the uncalibrated and calibrated data, that way as we improve our calibration methods we can go back and improve the data from past work.