Universiteit Leiden

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Radiation can be used to determine the isotope ratio of a skeleton. This provides information about where our ancestors lived and what they consumed. Dr Andrea Waters has developed a revolutionary method that can trace patterns of consumption from tens of thousands of years ago.

Isotopes are stored in human bones, even when the person died hundreds of years ago. We know what the isotope ratio is in many parts in the world. By comparing the data from the bones with the ratios in the world, you can investigate where a person comes from. This supplements knowledge about patterns of trade. Which people were in contact with each other? Did groups of people migrate and from where?

Alongside isotope ratios that equate to the location, there are also isotope ratios that change according to the food that you eat. We then look at other elements such as carbon and nitrogen together with hydrogen and oxygen. Rice and barley contain a lot of carbon with isotope number 3 (C3). If an archaeologist finds a lot of C3 in bones, it means that this person ate a lot of plants with a high C3 content.
As well as nutrients, your body also absorbs water. Water consists of hydrogen and oxygen atoms. If we look in detail at hydrogen, this comprises different sorts of hydrogen isotope: H1, H2 and H3. The ratio between these three isotopes differs according to the provenance of the water. Water at the coast is different from water on the mainland, and equally, water in a warm country has a different ratio from water in a cold country.

The skeleton constantly renews itself. The isotope ratio in the bones changes as a person eats new food or moves to another location. The same is not true for the teeth. They remain in the state in which they developed. This means that they contain the isotope ratio of a person’s childhood.

New technology unlocks material more than ten millennia old

The current method of reading the isotope ratio from bones is not reliable for bone matter that is older than 10,000 years. Dr Andrea Waters developed a method that would make it possible to study material that is more than ten millennia old. She used a Synchrotron for this, a particle accelerator that propels radiation through the bones to read their isotope ratio.

Dr Waters use this new method to conduct research into breastfeeding in old Hominidae. She suspects that Neanderthals (who lived between about 200,000 and 32,000 years ago) fed their children differently from modern humans. ‘It could be that the Neanderthals breastfed their children for much longer or much more often. This meant that they could not have a subsequent baby as soon and that they did not reproduce as quickly as modern humans do.’ This could be the reason for the extinction of the Neanderthal,¬ a mystery that archaeologists have been investigating for decades.

In her research Andrea Waters works with Professor Hanna Swaab, Professor of Education and Child Studies at Leiden University. Hanna Swaab researches the social aspect of breastfeeding within a society. How important is breastfeeding to a good bond between mother and daughter? And has this bond changed in recent centuries? This knowledge helps Swaab and Waters create a more detailed picture of the mother-child relationship centuries ago.

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