1. Bubbling over: archaeological lipid analysis and the Irish Neolithic: Review
Originally posted online on 6 March 2012 at rmchapple.blogspot.com
(http://rmchapple.blogspot.co.uk/2012/03/bubbling-over-archaeological-lipid.html)
I recently attended one of the PCC Lunchtime Seminar Series talks (Booms and Busts in
Europe’s Earliest Farming Societies given by Prof. Stephen Shennan) at the School of
Geography, Archaeology and Palaeoecology at QUB. It was a fascinating talk that I
enjoyed very much and I decided that I would make every effort to attend the next one.
Yesterday (6th March 2012) we had Dr. Jessica Smyth, currently of the Organic
Geochemistry Unit, in the School of Chemistry, at the University of Bristol, speaking on
the topic of lipid analysis and their application to the study of the Irish Neolithic.
She began by introducing the topic of lipid analysis, explaining how it involves the
investigation of surface and embedded fats to reconstruct past diets. This field of
research was largely pioneered by Prof. Richard Evershed and Smyth explained how she
is working closely with him on this post-doctoral research project. She explained that
one of the thrusts of her PhD research (Neolithic settlement in Ireland: new theories
and approaches, completed at UCD) was to provide a counterpoint to the traditional
narrative of the Irish Neolithic. In the past much of the debate had centred on the
megalithic tombs and the relatively small number of excavated houses. However, by the
early to mid 2000s, much new and challenging evidence was being uncovered as part of
the large infrastructural projects and the topic was ripe for re-evaluation (See my take
on the benefits of the ‘Celtic Tiger’ years here). One of the bounties of the ‘Celtic Tiger’
period was the vast increase in recovered ceramics, many of which may have been
suitable for lipid analysis. Following on from her PhD, Smyth applied to the Marie Curie
Actions foundation and was awarded a Marie Curie Intra-European Fellowship for
Career Development for lipid analysis for the ‘SCHERD’ project. ‘SCHERD’ stands for
“Study of Cuisine and animal Husbandry among Early farmers via Residue analysis and

2. radiocarbon Dating” and, as these things go, is a pretty snappy title for the project and
gets all the main points across.
The first question that Smyth posed was ‘why is it important?’ She emphasised that the
Neolithic is a significant stage in human development with the introduction of
megalithic architecture, farming, and generally increased social complexity. Lying at the
edge of Europe, Ireland is also chronologically and geographically at the end of this
process, which makes an even more interesting research proposition. She explained how
her research interests partially overlapped with those of the LeCHE group, a
confederation of researchers examining the origin of dairying in Neolithic Europe
through the use of lipid analysis, DNA etc. However, their research focuses on central
and south-eastern Europe, leaving Ireland previously unstudied.
The aims of the SCHERD project are to firstly identify the contents of the pots via lipid
analysis. This is particularly important in the case of Ireland where generally poor
preservation of animal bone has constricted our ability to understand some of the
developments and mechanisms of Neolithic agriculture. In this way the analysis of lipids
may be developed for use as a proxy for the economy of the past. It is also hoped to
distinguish patterns of regional variation that may shed light on differing diets,
economy and traditions. It is also hoped that, similar to the research carried out by
Mukherjee et al. (2008) for England, that diachronic changes may be discerned, such as
a change in emphasis on cattle rearing to pig production. Another aim of the project is to
provide more secure date markers for the Irish Neolithic by directly dating surface and
absorbed residues from selected vessels in key assemblies. In this way, it is hoped to add
to or, assist in the revision of, Bayesian chronologies for the Neolithic, a process begun
with the volume Gathering Time: Dating the Early Neolithic Enclosures of southern
Britain and Ireland. Smyth also highlighted the problem that much of our chronology of
the Irish Neolithic is relatively poor as it is based on typological assessments, chiefly of
changing pottery styles. For all of these reasons, the chronology requires urgent revision
and the SCHERD project hopes to play a prominent role in that process.

3. Smyth outlined her sampling regime of 15 key sites, spread across the entirety of the
Irish Neolithic. In the Early Neolithic her sites include two enclosures (Donegore Hill,
Co. Antrim, and Magheraboy, Co. Sligo) and five houses (including Ballygalley, Co.
Antrim, and Monanny, Co. Monaghan). The sites from the Middle Neolithic included
one enclosure (Tullahedy, Co. Tipperary), two pits (including Goodland, Co. Antrim),
and one pit/spread. The late Neolithic sites examined by Smyth include one enclosure
(Ballynahatty, Co. Down), one spread (Longstone, Co. Kildare), one house
(Ballynacarriga, Co. Cork), and one pit (Lowpark, Co. Mayo). To ensure that a
statistically viable sample was investigated, where possible, a minimum of 30 sherds
were examined from each site. As Smyth points out, the lipid analysis process is
destructive. However, she argues that considering the potential rewards in terms of new
data and insights, the removal of 2-3g of pottery per analysed sherd is a pretty minimal
price to pay.
The process of preparing the sherd is as follows: the surface is cleaned with a modelling
drill to remove all forms of surface contamination. To release the lipids from the clay
matrix of the pottery, the sample is ground into a fine powder. The resulting dust is
placed in furnaced glass phials and solvents are added to release the lipids. The solvents
used are most usually of the form of chloroform/methanol compounds. After some time
the resulting complex mixture is purified and separated. The resulting Total Lipid
Extract (TLE) amounts to approximately 2ml. This is kept in refrigerated storage and all
analyses are conducted using small portions of this core sample. The TLE is further
treated to make it suitable for use in various tests, including use in a mass spectrometer
or a gas chromatograph. Only once all of these steps have been completed can analysis
actually begin.
Smyth explained that one of the research aims pursued by Prof. Evershed was that
extensive experimental work was necessary to provide a library of lipid signatures that
would allow researchers to confidentially infer the former presence of fats. She showed a
number of chromatograms showing Triacylglycerol signatures (TAGs). She also
explained how, over time, these degrade into Diacylglycerols (DAGs) and then
into Monoacylglycerols. Finally, these will degrade into simpler, free fatty acids. Lipids
recovered from archaeological sherds are most usually of this latter type. It is estimated
that of the original volume of deposited lipids, only 1% is likely to survive. Some of the
sites investigated show excellent rates of survival (such as Tullahedy, Co. Tipperary),
though survival rates are thought to be related to variables such as climate and
temperature etc. As an example, Smyth cited research work carried out in dry countries,
such as Greece. Here, less than 10% of sherds retained lipid traces. Experimentation has
shown that there is vast and rapid degradation of the lipid remains on sherds stored in
aerobic conditions over a 40 day period. It is for this reason that the sherds selected for
this form of analysis should come from sealed, anaerobic contexts. Smyth also noted
that the storage of sherds in plastic bags (extremely common these days) may also leave
a lipid signature on the pottery. Her concern is that while it is not an insurmountable
problem, it does need to be noted and it may also mask genuine archaeological signals.
In examining what makes a high quality sample, Smyth noted that upper body sherds
and rim sherds have shown the best level of survival. At face value, this seems counter

4. intuitive as this is the region in least contact with any boiling liquids in the pottery
vessel. As noted above, sherds from sealed, anaerobic contexts are also preferred over
finds from the plough soil etc. It is also important that finds are well archived and are
retained with their meta data, indicating their contact with plastics and other forms of
post-excavation processing. While, from a chemical point of view, the need for sherds
from well stratified deposits is not essential, it is of the highest archaeological
importance so that the fullest data may be relayed back into our site models. Finally, it is
always good to have a complementary faunal record or other proxy data against which to
compare results.
Addressing the question of the feasibility of this project, Smyth noted that earlier work
on the Tullahedy, Co. Tipperary, assemblage reported a rate of five out of six analysed
sherds retaining lipids. At another Middle Neolithic site on Rathlin Island, Co. Antrim,
50 sherds were analysed. This showed a recovery rate of 28 of the 50 analysed sherds
containing lipid residues. Smyth was also keen to stress that, with 14 months left to run,
she is still at a relatively early stage in her project and the results she has thus far
obtained are preliminary in the extreme. With regard to the site at Donegore Hill, Co.
Antrim, the recently published monograph and the Gathering Time volumes have
provided a secure dating range. Given the enormous quantity of recovered ceramics (c.
45,000 sherds), only the rim sherds were formally analysed. These were estimated to
represent approximately 1,500 individual vessels. Unfortunately these sherds were
unavailable for lipid analysis. As none of the body sherds were identified to individual
vessels, a selection of fabric types was selected, spread across the entirety of the site. At
the Neolithic house site at Ballygalley, Co. Antrim, the upper body and rim sherds were
available for analysis, though the results of these analyses are yet to be completed. The
enclosed Middle Neolithic settlement at Tullahedy, Co. Tipperary, produced a very rich
cereal assemblage – in fact it is the most abundant assemblage of its type throughout the
entire Irish Neolithic. However, the site had remarkably poor bone preservation. Earlier
investigations of some sherds from Tullahedy confirmed the presence of free fatty acids
on a high proportion of the examined sherds. While early results are promising, she was
quick to stress that further analysis, including isotope ratio analysis, would be necessary
to confirm them.
Looking towards the future of the SCHERD project, Smyth hopes to document the
changing nature of Irish agriculture over time. Evidence from such sites as the Céide
Fields, Co. Mayo, and Kilshane, Co. Dublin - the latter with its exceptionally large Late
Neolithic assemblage of animal bone – have been taken to suggest that there was a move
away from a cereal-based economy to a stock rearing economy over the course of the
Neolithic. Smyth believes that with enough good quality samples, and sufficient time on
the various machines, the SCHERD project can make significant contributions to the
state of our knowledge.
In the question and answer session at the end of the presentation, Smyth was asked if it
was possible to date lipids directly, using radiocarbon dating. She replied that it did
appear to be possible, though they had not attempted it so far. For example, some of the
sherds, especially those from Donegore Hill, had produced over 5mg of lipid residue,
more than enough for an AMS date, so the potential is definitely there. Smyth was also

5. asked if it was possible to distinguish between sheep and cattle in the lipid residues. She
explained that it was, though the analysis of subtle differences in the signatures of
Triacylglycerol (TAGs) and Diacylglycerols (DAGs). One other contribution related to
the description by Peacock, during an 18th century tour of the Hebrides. He had
witnessed the native islanders creating coil-built pottery vessels and firing them in open
hearths – essentially the same manner as in the prehistoric past. However, Peacock
noted that before they were placed in the hearths, they were filled with milk, which was
allowed to evaporate during the firing process. The question then was that could this
form of activity be what we are witnessing, rather than the continued use of the vessel to
hold a variety of different cooked meals. Smyth admitted that it could complicate
matters, but that it was most likely that the firing process would not just evaporate the
milk, but destroy any lipid residues in the process. One further intriguing problem was
raised during this discussion. This was the discovery of certain keytones in some
samples that indicate that the contents were fired to a temperature over 300°. While it is
thought that the average open heath would struggle to achieve this temperature, the
reality is that little food would survive for long even if it could be achieved.
As Smyth stressed throughout this presentation, she is currently only able to present
preliminary results. Nonetheless, she has already produced some interesting, and
potentially controversial, findings. I, for one, eagerly await her return trip to Belfast
when she has been able to fully verify her findings and process more samples.
Notes:
I hope that I have done justice to Jessica Smyth’s lecture and managed to convey the gist
of her ideas and results. Nonetheless, I do sincerely apologise if I have misrepresented
or misquoted the speaker. If so, please feel free to contact me, and I will endeavour to
set the record straight.
I have not been able to give the full references to any of the literature referenced in the
lecture – sorry.
Some photographs of the 1984 season of excavations at Donegore Hill are available for
public viewing, at The William Dunlop Archaeological Photographic Archive.