Chemistry reveals ancient diet

It was a technological innovation with a greater impact than the iPad: pottery. Pottery made it possible to extract more nutrients by cooking, prepare nourishing stews, detoxify plants, wean children and so on. It was therefore an invention with enormous implications for diet and human health. It also created new culinary possibilities.

Traditionally it was thought that pottery was invented in the Near East at around the same time as that other great invention: agriculture. But in the last decade, evidence has accumulated to show that it was in fact invented almost 20,000 years ago (towards the end of the last Ice Age) by hunter-gatherers in the Far East.

A new study has now revealed the diet of these hunter-gatherers, with the help of both chemistry and physics. And more importantly, it tells us why these people started to use it in the first place. The results have been published in the science journal Nature, and Peter Jordan, the new Director of the University of Groningen’s Arctic Centre, is one of its authors.

Pottery was often used for cooking, and the sherds of cooking pots can contain residue of the original contents. So far, scientists have looked for traces of milk from domestic cattle in the pottery of Neolithic farmers. This is much easier than identifying wild foodstuffs (such as wild plants, fish or animals) from 15,000-year-old residues. Such a comprehensive analysis of the world’s oldest pottery had never been done before. Jordan says, ‘We had no idea whether the lipids would be preserved, or that we would be able to extract and identify them, and link them to specific foods’.

Using advanced gas chromatography techniques, team members from the University of York managed to analyse lipids from residues on old pottery sherds from Japan. Fat from fish or marine mammals has a different lipid spectrum from, for example, fat from terrestrial mammals. The lipid analysis showed that the hunter-gatherers had cooked marine foodstuffs such as fish. Furthermore, the lipid profile suggested that the fat had been heated to temperatures over 270 degrees Celsius. This not only showed that the pots had been used for cooking, but also ruled out the lipids being contaminants from the soils in which the ancient pieces of pottery were preserved.

The scientists used another technique to confirm the lipid results: they analysed stable isotopes of carbon and nitrogen in the samples. Stable isotopes are non-radioactive atoms that can vary in their atomic weight; for example, most carbon atoms have an atomic weight of 12, but there is also the heavier carbon-13. As different plants or animals often handle different isotopes differently, this produces a distinctive signature, distinguishing for example marine from terrestrial animals or ruminants from non-ruminants.

‘These findings are very important because they represent the first direct evidence of how early pottery was actually being used’, Jordan explains. ‘Prehistoric hunter-gatherers were clearly starting to use pottery as part of a wider strategy for processing marine and freshwater fish’. They did this at a time in which the earth’s climate was changing rapidly.

The earliest pottery was made before the end of the last Ice Age, but the use of pottery really took off during the Holocene, when the climate had become warmer. Ceramics may have been used to process seasonal gluts, such as an abundance of spawning salmon in a river. ‘Our results help us understand the dynamic relationship between humans and their environments during phases of major climate change’, Jordan explains.

The results also demonstrate that it is possible to analyse organic food residues from some of the world’s earliest ceramic vessels. Jordan and the rest of the international research team are looking forward to examining how prehistoric hunter-gatherers were using early pottery in a range of other periods and geographic regions, and how the art of pottery travelled from East Asia through Siberia and Russia to Northern Europe.

See also this University of Groningen press release.