On the 4th of February, 2013, at a press conference in Leicester, the astounding news that the remains of King Richard III had been found in a car park was announced to the world. In the weeks and months leading up to that announcement, experts at the University of Leicester had been meticulously analysing the skeletal remains uncovered in the Greyfriars dig.

Our intern Emily has written a few blog posts explaining some of that careful analysis, and how the results led the University of Leicester team to this conclusion.

Carbon and its isotopes

Carbon is an essential building block of biological molecules which is present in all living things. Plants absorb carbon from the atmosphere, animals obtain carbon through their food. Carbon exists in different forms, known as isotopes. Isotopes refer to atoms of the same element which have different numbers of neutrons (a subatomic particle). There are three naturally occurring isotopes of carbon: Carbon-12, Carbon-13 and Carbon-14. Carbon-12 and Carbon-13 are the most abundant whereas Carbon-14 is only found in trace amounts, one in every trillion atoms, to be precise!

How is Carbon-14 used in radiocarbon dating?

Radiocarbon dating is a technique used to determine the age of organic objects using Carbon-14. This is commonly used in archaeology to calculate the age of skeletal remains. Carbon-14 is radioactive and is continually formed in the atmosphere, where it is taken in by living organisms. Compared to Carbon-12, Carbon-14 has two additional neutrons, making it unstable. As a result, Carbon-14 begins to degrade when an organism dies, in a process known as radioactive decay. Carbon-14 has a half-life of approximately 5568 years, meaning that it takes ~5568 years for the amount of Carbon-14 to degrade to half its original amount. The principle behind carbon dating is that older carbon-based objects will contain less Carbon-14 compared to younger objects. By using the half-life of Carbon-14, it is possible to determine the age of a carbon-based object. However, there are additional factors to consider.

Although the proportion of Carbon-14 is the same in both the atmosphere and living things, this is not the case in the oceans. When carbon dated, marine life can appear up to several hundred years older than they actually are. This can also affect the proportion of Carbon-14 in land-based animals which consume fish.

How was radiocarbon dating used in the identification of Richard III’s remains?

Radiocarbon dating was performed on the skeletal remains discovered during the Greyfriars dig. As Richard III died at the Battle of Bosworth in 1485, the remains, if they were those of Richard III, should date back to this time period. However, two separate radiocarbon dating tests from the Scottish Universities Environmental Research Centre and the University of Oxford dated the remains to between AD 1430-1460 and AD 1412-1449, respectively. This didn’t match with what we know about Richard’s date of death, did this mean the remains were not those of Richard III?

Actually, scientists have come across this problem before. A diet rich in fish and seafood will affect an individual’s Carbon-14 results. As I mentioned earlier, marine life contains more Carbon-14. As a medieval nobleman, Richard would have eaten fish during fast days, and there were many fast days in the medieval calendar. So this discrepancy can be explained by Richard’s diet, and by taking this into account during the analysis, it was revealed that the remains belonged to an individual who had died between AD 1460-1540, which is consistent with Richard’s death in 1485.

To find out more about carbon isotopes in the diet – and why Richard III ate so much fish! – look out for our blog on stable isotope analysis.