Our series of blog posts by Emily continue with this delve into what else isotopes can tell us. Part one of Stable Isotope Analysis tells us about how we literally are what we eat!
What is stable isotope analysis?
In our previous blog post on Radiocarbon dating, we discussed how Carbon-14 is used in radiocarbon dating to estimate the age of skeletal remains. Carbon-14 is an unstable isotope of carbon which undergoes radioactive decay. Unlike Carbon-14, stable isotopes are not radioactive and do not decay over time. Our bones and teeth contain stable isotopes of oxygen, strontium, nitrogen, and carbon. The composition of these isotopes can tell us where someone has lived, as well the type of food and drink they have consumed. We can find this information from specific stages of a person’s life by using different parts of the skeleton.
Our bones undergo continuous replenishment throughout our life. Rib bones are frequently replenished, representing the last few years of an individual’s life. The femur is replenished at a slower rate, representing the last ~10 years of life. Unlike bone, teeth are formed during childhood and do not replenish, so they can tell us about an individual’s childhood. Isotope analysis was performed on Richard’s teeth, femur and rib bones to determine where Richard lived and what he ate during his life.
Where did Richard live?
Oxygen and strontium isotopes can tell us about where an individual lived. The make-up of strontium isotopes can tell us where an individual’s food was grown whereas the make-up of oxygen isotopes can tell us the source of drinking water. As strontium and oxygen isotopes become fixed during tooth formation, it was possible to determine where Richard lived during his childhood through dental isotope analysis. The low oxygen isotope ratio suggests that Richard spent his early childhood in eastern England. This is consistent with his known birthplace in Northamptonshire (Fotheringhay Castle, 1452).
Interestingly, the oxygen isotope ratio peaked when Richard was 7-8 years old. Higher isotopic oxygen ratios occur in the west of England, in higher rainfall areas. This peak is also observed in the strontium isotope data, suggesting that Richard moved away from Northamptonshire during his childhood. This data agrees with records of Richard living at Ludlow Castle in the Welsh Marches in 1459. The oxygen and strontium isotope ratios remained low during adolescence and into adulthood, suggesting that Richard moved back to the east of England.
To find out about what stable isotope analysis told us about Richard’s diet as an adult, keep an eye out for Stable Isotope Analysis – part two!