Podcast: What our ancestors ate



3 February 2015 by Richard Hollingham

This week in the Planet Earth Podcast, in a geoengineering special edition, we take a closer look at some of the technologies we may have to resort to using to avert dangerous climate change.

To assist those who find text-based content more accessible than audio, a transcript of this recording is available below.

Richard Hollingham: This time in the Planet Earth podcast, how a few fragments of bone can tell us what our ancient ancestors liked to eat.

I'm Richard Hollingham and I've come to the Archaeology Department at the University of York, and in my experience archaeology departments are usually full of shelves stacked with boxes of bones, there's pots, there's relics. This is very different. This is a shiny white lab with chemicals, with test tubes, flasks, and you can hear in the background there are freezers and fridges, and with me, researcher Sophy Charlton, who is investigating the lives of pre-historic people living in the British Isles. I am also joined by Oliver Craig, the head of this facility. I say facility because you do something almost unique here with archaeology.

Oliver Craig: As you say, archaeology departments traditionally are known for storing lots of material and doing lots of excavation. What we specialise here at this part of the university is in analysing that material once it has come out of the ground. To tell stories about the past, but from the point of view of the biological remains that we find associated with artefacts or things like bones or shells or hair, occasionally.

Richard Hollingham: Now, this is the example then, Sophy... bones, fragments that you have analysed, they are essentially in a biscuit tin at the moment, where are these bones from?

Sophy Charlton: These bones are actually from the western isles of Scotland, they are from the Mesolithic period which spans from around ten thousand years ago to around six thousand years ago.

Richard Hollingham: Well, let's open the box up. It says 'fragile' on it. Let's have a look at what is in there? So, pull it open.

Sophy Charlton: Inside here I've got lots of different bits of bone but these are all really fragmentary bits of bone and when the original excavations were undertaken they were all labelled as unidentifiable. At the time they weren't able to be identified because they were all very heavily broken up because they are so old, they are very small pieces so we can't tell what animal they are from or what kind of element in the skeleton they are from.

Richard Hollingham: I should say they are all in individual bags, all individually labelled. Can we just have a look at one of these bags here? I mean they are tiny. They are the size of a finger nail, something like that, these fragments.

Sophy Charlton: Yeah. Generally they are very, very small but they do contain enough biological information that we can actually determine what species of bone the animal is from or indeed if they are human, and if they are human or indeed if they are animal what kind of things they were eating in the past.

Richard Hollingham: Where do these come from? These were from Scotland.

Sophy Charlton: These were from a small island just off the west coast of Scotland where it is known that people in the Mesolithic period were probably visiting these islands seasonally, so we think these people were migrating around the landscape, utilising different resources at different periods of time throughout the year. So these are the bits they left behind, essentially.

Richard Hollingham: So, Oliver, in this facility you can take fragments like this and how do you analyse them? How do you extract those chemicals and look at those signatures of the past?

Oliver Craig: Well what we have to do first is obviously grind them up so it is semi-destructive, but after that we extract out the protein part of the bone. There's plenty of protein in bone. The protein we're interested in is called collagen which you might have heard of; it is present in jelly and things like that. We take the collagen out, we purify it and then we take it to an instrument which we have in our lab just next door. The instrument is actually called a mass spectrometer and it measures different forms of the elements of carbon and nitrogen in these bones. And those different forms of this element vary according to what the person or the animal has been eating, and essentially we can reconstruct the diet of these organisms.

Richard Hollingham: So what did you find, Sophy when you did that?

Sophy Charlton: I found that actually these people were eating a very high marine diet, so eating lots and lots of different marine resources, so fish but also marine mammals, so things like seal. I also managed to identify some animal remains from the site and so I could compare the diets of the animals to the diets of the people, so it gave me an idea about the kind of things that people at that period in time were eating. For me it has been really interesting because they are from a time period where we go from eating a lot of marine resources and being hunter gatherers to being very domesticated with the onset of agriculture and then our diet changes to being mainly domesticated animals and cereals.

Richard Hollingham: So does this mean, Oliver, you can start up a picture of people and many of our ancestors from six thousand years ago in the British Isles?

Oliver Craig: Yeah and we can go back further than that but it is obviously dependent on the human remains that we have at our disposal. One of the problems with Britain it seems is that there are very little human remains dating back before this period, going back further in time. So we have a very poor record of human bones going back before six thousand years ago. One of the things that Sophy is trying to do is to identify new human remains that we can do these kinds of analyses on.

Richard Hollingham: And these are often remains, Sophy, that have been around... I mean these, for example, were found quite a while ago and only recently analysed.

Sophy Charlton: Yes, these were actually excavated in the late 1970s but it is only with the advent of more recent scientific techniques that we can extract this kind of useful information. But there is an awful lot of material which is sitting in museum archives and at universities which has previously not been studied because it is very fragmented, it is very broken up, it is very small and so looking at it just with your eyes you can't tell what it is, it's not that useful but with the new scientific techniques that we've got we can actually get this kind of useful scientific data out of them.

Richard Hollingham: Does that mean, Oliver, that you've now started to build up a picture of how diets have changed over the thousands of years between then six thousand years ago and now.

Oliver Craig: Exactly that. That is one thing we're really interested in and also looking at the significance of that. The arrival of agriculture is one of the big things that transform Britain about six thousand years ago and it is that process that we really need to have a handle on. Obviously if you think of our cultural evolution and our dietary evolution agriculture is one of the key things that has changed. The opportunities for farmers but also health implications we well, that big dietary change which is still significant today if you think about for a long time we were hunter gatherers, we were accessing a whole broad range of food resources and then suddenly we went down to just these very few domesticated foods. One of the other things we're very interested in is understanding what that dietary change, how that impacted on our health.

Richard Hollingham: Presumably, I mean, the way we live today we still eat fish and if you live in a coastal community you would expect perhaps to eat more fish than you would if you were living in the centre of the land. Can you draw parallels with how we live today with how we might have lived?

Oliver Craig: You would have thought that and one of the really interesting things that has emerged from this research is that during the Neolithic period which is the period immediately after the arrival of agriculture, what we see is that they don't seem to be eating that much marine foods. Before the site here, which which Sophy has been analysing they seem to have a lot of marine foods in their diet but suddenly it seems that they seem to have turned their backs on the sea and be focusing more on cereals. Now, there is a big argument about how quickly that happened and how complete that transition was but it does seem to be a major significant change in the people in the British Isles over the last ten thousand years.

Richard Hollingham: Can we draw any parallels with diets that are around at the moment? For many people, certainly in the west, we have choices so we could have a more hunter gatherer-type diet or a more cereal-based diet.

Oliver Craig: And people, of course, advocate things like the Atkins diet, which is the high protein diet which is meant to be better for you, the ancestral diet, the hunter gatherer diet, low in carbohydrate, rich in animal and marine protein. Now that is a very legitimate question to ask, is that dietary change healthy for us. Considering that we have adapted probably for many thousands of years before agriculture to digest wild foods suddenly forcing ourselves to focus on these carbohydrate-rich diets is a question that has to be asked and lots of diseases, like forms of diabetes are thought to have stemmed from this quick dietary change. So looking at the health implications for this is very important. Today, although we have access to all these fantastic marine foods in the British Isles, how much fish is actually eaten by the average person in Britain, very little, and that is one of the really interesting things. We still rely so heavily on carbohydrate despite our vast coastlines.

Richard Hollingham: Oliver Craig and Sophy Charlton here at the University of York. Thank you both. If you would like to see what these bone fragments look like we will put some pictures up on our Facebook page and Tweet them too. That's the Planet Earth podcast, part of Planet Earth online from the Natural Environment Research Council. I'm Richard Hollingham from a laboratory here in York - thanks for listening.