Women in Science: Milking it – How small molecules from ancient pots tell us when humans first started dairying
Julie Dunne began life as an accountant for a construction company. She took to science as a mature student, and now, in her 50s, she is in her third year of her PhD in biomolecular archaeology at the University of Bristol. She is using molecular and isotopic analyses of absorbed food residues from 7000 year old ceramics from the Libyan Sahara to identify the inception of dairying practices in Africa. Julie took part in Soapbox Science 2013, on 5th July where she stood on a soapbox on London’s Southbank and spoke to the public about her work, and to help promote the role of women in science. www.soapboxscience.org
As a biomolecular archaeologist, I am passionately interested in how people lived in the past. In particular what excites me most about what I do is how science helps us to answer broad scale archaeological questions, such as the timing and spread of what is known as the Mesolithic-Neolithic transition. This period, beginning around 10 -12,000 years ago, denotes the time that ancient humans moved from a mobile hunter-gatherer lifestyle to a more settled farming way of life.
The Neolithic, or New Stone Age as it is commonly known, is generally associated with the first pottery production and the domestication of plants and animals such as cattle, sheep and goats. This move to an agricultural lifestyle and thus the inception of dairying economies allowed significant population growth, had substantial effects on human diet and health. It resulted in considerable changes to ancient subsistence economies which, in turn, led to increasing urbanization, the rise of complex societies and, finally, to today’s information age.
So why is it important that we study this period of enormous cultural, economic and biological change? Dairying by these early farmers led to the beginnings of humans using products such as milk, butter and cheese which can be extracted from an animal throughout its lifetime, making them ‘walking larders’.
As well as tasting good, milk must have been an incredibly important food resource to ancient people. It is one of the few foodstuffs which contains all the things humans need nutritionally – fat, protein and carbohydrate – together with important vitamins and minerals, as well as being very important for bone health.
We now know that it is the beginnings of dairying by these first farmers which led to the evolution of the lactase persistence gene. Because of this evolutionary event, most Europeans today can drink milk and eat dairy products without experiencing the unpleasant symptoms of lactose intolerance. The evolution of the lactase persistence allele is a direct result of the Neolithic human change in dietary practices and a remarkable example of natural selection in action over a relatively short period of about 1000 years. This transition also laid the foundations for the multi-billion pound European dairy industry as we know it today.
How might we attempt to identify the timing and spread of dairying of the earliest European farmers? Luckily, ceramic vessels, used by these first farmers to store or process foodstuffs, are the original non-biodegradable object made by humans and consequently survive over long time periods.
Fat floats on water: when you boil meat or similar foodstuffs in a saucepan small globules of fat will rise to the surface. These globules are made up of lipids, the building blocks of fats, and are found in animal fats, plant waxes, fish, resins and beeswax. As ancient humans cooked food products in their pots these lipids, comprising mainly of fatty acids, migrated into the porous vessel walls.
The pot then works like a sponge and absorbs the lipids into the tiny holes in the ceramic matrix, which, as the fats rise to the top, concentrate in the rim of the vessel. They are so well preserved within these pores that they have been found to survive over time scales of thousands of years (until excavated by archaeologists!).
Using various chemical and analytical techniques, we examine these lipids and use their characteristic distributions to determine what sorts of foods people were cooking, different lipid profiles might suggest ancient animal fats, plant waxes or marine products such as fish. So how might we confirm that these fatty acids we find in these pots come from the meat of the animal or from their milk and its products such as butter, cheese and yoghurt?
We do this by measuring the isotopic composition of two particular fatty acids, the C16 and C18, found in both the milk and the tissue of ruminant animals such as cattle. Whilst the amount of C16 fatty acid remains constant in both milk and the animal flesh as it originates from dietary carbohydrate, the C18 fatty acid occurs in different concentrations as the mammary gland cannot synthesize the C18 fatty acid and sources it from dietary fatty acids (from the plants eaten by the animal), which are produced in the rumen. This allows us to differentiate between fat sources and thus identify the first European farmers.
I’m eager to demonstrate to anyone who has a passion for science, yet are not working in a related field, that it is always possible to change career and become involved in science, no matter how old you are. I took an undergraduate degree and a Masters as a mature student and am now in my third year of a PhD in the Organic Geochemistry Unit at the University of Bristol. Being able to follow my passion for science and archaeology, and share that with others, has enriched my life enormously.
More information about the Organic Geochemistry Unit at the University of Bristol is available hereTagged in: women in science
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