Dr Tamsin O'Connell, Department of Archeology, Cambridge University
Part of the show Dinosaurs, Ancient Diets and Fossilised Crocs
Tamsin - I work on more recent dead bodies including both humans and other animals. By looking at the chemical composition of bones and tissue, we can find out what they ate, how they lived and how they moved around the environment. People in the past ate a lot more protein and fat, and ate fewer carbohydrates. This isn't too different to today's Atkin's diet! Our work is interesting because it gives us an insight into what animals were eating and how they lived their lives.
Chris - Your work has shown that animals literally are what they eat! Tell us how it works.
Tamsin - It works on tracing chemical signals from foods into your body tissues. When you eat, food gets broken down and molecules get re - synthesised as your hair grows; your skin grows; your bone grows, and so on. If you can find a marker that is in the food and is unchanged by the process of being incorporated into your body, you can then track things about people's food both now and in the past.
Chris - So what is the marker that you're using?
Tamsin - We are all made up of not that many elements: carbon, hydrogen and oxygen. These elements come in different forms and these forms are known as isotopes. This basically just means that there are two forms that weigh slightly different amounts. I can then trace the ratios of the different isotopes in your hair and look at where they came from.
Chris - How far back in time can you go?
Tamsin - As far back as the material is there to survive. If material is kept in good condition, I can go back a very long way. I have looked at mammoths back to 200 000 years. In hotter places, I would be lucky to go to 2000 years. Tooth enamel is the best because you can go back 15 million years, and has allowed us to look at many marine animals. We can find out things such as what fish animals were eating.
Kat - How can you use the information you get to tell us about societies?
Tamsin - How people gathered their food tells you a lot about how they spent their time and lived their lives. If they ate fish, they must have had technology such as nets and hooks. If they ate a lot of meat they would have needed technology and ability to hunt. If eating plants such as cereals then you must have horticulture skills, farming technology and the social structure in order to do that. So by looking at what they ate you can say quite a lot about their society.
Kat - Can you find evidence of things like drug use?
Tamsin - You can but not using the same technique I use. A number of people are looking for that. Effectively they look for the breakdown products of drugs. Sometimes you can find those molecules preserved. Some people have recently found drug breakdown products in mummy hairs.
Chris - What can your technique tell you about what people ate?
Tamsin - It works on quite a broad brush level. We can say things like 'were these people having lots of plants, and were they these certain types of plants?'. We can tell when people have been eating maize because it makes a big change in bone isotope signals. This has helped, especially in the Americas, to see when people were changing from the hunter-gatherer lifestyle towards farming. Another big change in human history is that up to about 13 thousand years ago we weren't eating fish. It seems that we were much keener on eating large terrestrial mammals. We seem to have exploited land animals first and then 30 000 years ago turned to alternative and smaller food sources. It does require a slightly finer degree of tool making ability.