Dear SHARPies: Some of you will remember me from last year, thrilled to be scrabbling around in the gully of mussels. The 2009 season once agin showed the good numbers and excellent preservation of the marine shells at Sedgeford. Most of you saw the early ditch terminal central to Trench 10 containing a dense group of animal bones (including a semi-articulated cattle skelly), strewn with mussels. The preservation of these mussels was, frankly, the best I have seen in my 15 years of looking at archaeological shells. It's almost impossible to recover mussels in a good enough state that they can be compared with modern mussels (probably the world's most studied type of shellfish).

I have (I hope) attached a short report about these mussels (as an Adobe .pdf document), as a thank-you for my entertaining week at Sedgeford, and to de-mystify what it is that I am trying to do with the Sedgeford shells. Please be patient if this attachment stuff doesn't quite work out first go. I look forward to your comments and questions.

Greg Campbell

I agree it is a fascinating document and I am still trying to understand the information. However I have a couple of questions or comments.
On page 1 is the rapid burial burial the only reason for the good preservation or is there some factors involved.

On page 3 does the age of the mussels suggest they were special in some way and I just wondered if the slow growth was significant. It also suggests that they were from high on the shore which seems to contradict the sheltered conditions and I wonder how this relates to the slow growth and age of the mussels.

I might have misread the document so apologies if this is incorrect.

Well, hurrah, the attachment attached! And thank you Soph. And to keep things anarchic I will speak to Bill and come back to Dave.

I do hope that this .pdf gets to live on the post-ex area when it has sat here for some months and been read and commented on by the SHARPies, and re-drafted with their comments (like Dave's questions) addressed. There is always a specialist jargon and specialist assumptions about background knowledge that needs to be corrected or expanded to make the report useful for everybody on the project. So read through and comment away. There is already a report on the mussel-rich gully from 2008; is that living somewhere on the post-ex site?

Hallo Dave. The good preservation has three causes. (1) The preservation of the marine shell at Sedgeford is, generally, excellent (not just better than most sites, but better than almost all sites). The type of soil is just right to keep the degradation of shells (and it seems faunal remains generally) to a minimum, in the face of centuries of English rain washing through the ground. Almost all the animals that they made use of and discarded are still where they were discarded. This alone makes the site an important one to understanding the Saxon rural way of life.

(2) Even better, the type of soil at Sedgeford is coarse and loose, making the getting the shells out of the deposits without busting them up in the process. So, damage during recovery is also minimal. Geting shellfish out of sticky Midland clay or Downland chalk rubble means most of them are bust. This lifts Sedgeford from important up to regionally imprtant. (my next concern is retrieval bias: what is sitting in the deposit is not what you get out of the deposit when you excavate it, and sometimes the difference leads to mis-understanding the past).

(3) The rapid burial in 10510 is the reason that the valves were whole (not fragmented by being crushed against each other), paired (as they would have been just after cooking) and inter-locked (as they would have been in the basket or sack used to take them to their final resting place). This is why they are measurable. And that lifts them from excellent to nationally important. They are almost certainly the best mussels from a Saxon rural site, and possibly from an English rural site (I have never heard of any better). Comparable metrical work is usually only attempted on upper Palaeolithic-Mesolithic cave sites.

Growth Rate: mussels get their food by filtering plankton from sea-water (some life!), so they grow fastest where there is lots of plankton (like shallow bays regularly flushed with fresh sea-water by the tide), and mostly where they have lots of time to filter sea-water (so sub-tidal mussels grow very fast 'cause they can filter all the time, but mussels near high-tide grow very slow because they can filter sea-water only a couple of hours a day). So the growth rate tells you mostly the tidal height being harvested.

Shelter: exposure to a marine biologist means the extent to which the shore is exposed to wave-beating, not to the air (that's called dessication time, or drying height). Wave-beaten promontories are very exposed, estuaries in the back of large bays are very sheltered. So you can be a mussel low on a very exposed shore, high on a sheltered shore, and lots of places in between.

Age: Age and growth rate tend to vary systematically with the tidal level on a given shore. Low down, you can filter lots and grow fast (high growth rate), but there are lots of things (viruses, bacteria, parasites, predators) to kill you (short life, therefore low average age). High up, you can filter ony a few hours a day (slow growth rate) but the things that kill you also have only a few hours a day to find you (long life, therefore high average age). Age and growth rate also varies with exposure (to wave-battering, not air, remember!). Sheltered shores mean its' easy to feed but easy to get killed (fast growth, low average age), wave-exposed shores mean it's hard to feed but hard for killers to get you (slow growth, high average age).

It was really interesting to read this - although I will have to go over it a few times to fully understand it!
Greg's comments about the national importance of these shells is also exciting.
Greg - with regard to the oyster shells - I have recently found a reference to these in the Wash as follows:
Blomefield's History of Norfolk - relating to the Hunstanton Lordship "Here on certain great refluxes of the sea, called a dead neep (tide) about the end of September, the inhabitants of the neighbouring villages can walk or ride about two miles to a place called the Oister-sea where they take in their season great quantities of oisters, some lobsters, etc..."
Our neep tides here in September this year were exceptionally low so it is not difficult to understand how in the Wash it would have been possible to walk out some distance.
Is it likely that the vast quantities of oysters at Sedgeford were all harvested at this one time of the year - and as you suggested, preserved for later consumption?
Bren

This is certainly a report that you have to read several times to understand but I was understanding the report to mean that the mussels had been transported rather than preserved but I could be reading it incorrectly.

I have seen some references to transporting shell fish to inland sites in containers of very cold water. To me this seems very difficult and how do you keep the water cold. However in our case it is only a short distance that the mussels are transported and in my original reading I though it was in a cooking pot but Greg refers to a sack or basket in his message.

I'd love to see references for that - but I'm afraid I rather doubt it as a viable method. The problem with oil preservation of things like shellfish would be that they contain a lot of moisture actually within the meats, which would allow bacterial action. You can preserve things like highly acid food (eg lemons) salted foods (eg anchovies) or finely chopped things (eg pesto) under oil because it excludes air but even then it only does a maximum of a couple of months unopened. Salting could work, but it would result in a seasoning like oyster sauce rather than a main foodstuff to be eaten for protein. You could dry them, but again the bulk would be so reduced that I'm not sure it's worthwhile.

In recent times oysters were transported in barrels of damp seaweed, in which they stay alive and therefore safe for up to a week, but I can find no references to preserving them in any culture except as part of making garum or oyster sauce.
Soph

I am both glad and sorry to hear that most of you are having to read the document multiple times (I'm sorry to hear it, but glad that you can tell me why it's a slog to read). Since this is a community project, I want to write a document that informs the whole community. So please do tell me what it is that is making the text tough to read, so I can fix it.

Preservation: A couple of comments about this. First, shelled molluscs know when they are out of the sea, and keep shut until they detect they are back in the sea, so they preserve themselves for some days. So keeping shellfish in their shells is the simplest way of preserving them if the journey to their final doom (our stomachs) is only a few days. (The literature on how many days a type of shellfish can survive is huge, but modern and therefore based on transport in refrigerated lorries, which makes it archaeologically irrelevant.)

However, most of a shellfish's weight is shell which we don't eat, so transporting it is wasted effort. If the journey is more than a few days, it is more sensible to separate the flesh from the shell before shipping it. So the logical reason shells end up on inland sites is that the people wanted those shellfish fresh, and transporting them that distance inland took only a few days.

Opening a live shellfish is fairly tricky and always messy (shellfish have shells to stop things getting in and eating them, after all). The simplest way of separating a shellfish from its shell is to kill it, so its shell-closing muscles fail and the skin that makes the shell (the mantle) come free of the inside of the shell. The simplest way to kill a shellfish is to cook it. This is pretty easy, only a short period (a few minutes) in high heat (which could be boiling water, steam, or hot air in ovens or hot embers) is needed. So usually shellfish are cooked to open them. This also kills the bacteria in or on the shellfish that cause rot, and draws out a lot of the body water from the flesh, making rotting by bacteria (that end up on the flesh after cooking) harder.

We really rapidly enter self-perpetuating archaeological mythology when talking about shellfish. The exact method used to cook shellfish in the past are not known well, and are something we can make guesses about. The well-preserved shellfish at Sedgeford give us an opportunity to examine them and look for signs of how they were cooked, which is why they are an important assemblage. Examination might involve highly complicated pieces of kit in shiny labs, using techniques that are only being developed or not even thought about yet. (I am speculating about the cooking causing measureable degradation in shell protein, which could be measured by protein assay, and the cooking temperature causing long-term changes in the excitation of the electrons in the crystals of shell, measurable by electron spin resonance).

Of course open cooked flesh is exposed to bacteria that cause rot, and these bacteria are always with us, so the cooked flesh would have to be preserved. And once again we enter self-perpetuating archaeological myths: The exact method of preservation would only be preserved well in the cooked flesh, which is almost never preserved (since the flesh is either eaten or rots away), so which methods of preservation were used is not very clear from archaeological evidence. There are technologically simple methods of preservation that work, so we know that it's possible for shellfish to be preserved in the past, but diagnosing which ones were used in the past, and where, is probably beyond us. These simple methods include air-drying in the wind under cover, smoking, salting, sealing in a container under oil (like sardines), and sealing in a container in solid animal fat (the French 'confit').

This cooking and preserving could happen in bulk on the quayside as a specialist trade, so the shellfish get preserved and then shipped inland. These shellfish have no shells when they end up at the location where they are consumed, so their consumption is archaeologically invisible. Trade in preserved shellfish is only archaeologically visible at coastal sites which have big heaps of shells. If shellfish are plentiful and transportation is easy and cheap, the shellfish can be shipped inland in their shells, and cooked and preserved at their destination. I think that it is this latter process that produced the gully full of mussels excavated in 2008.

Hey Dave! It's perfectly possible to get to season of harvest in oysters. Many shellfish lay down a thin layer every tide (even if they are below the low tide line), so you can count half-days (nearly; tides are not quite in synch with solar days). The amplitude of the tides waxes and wanes over a lunar month, so some shellfish have a banding pattern that repeats every lunar month. Most British shellfish slow down or stop growing in winter, forming an annual ring on the shell. If you can assume that the annual ring is winter and growth re-starts in spring (March, say), you can cross-section the shell hinge, polish and etch it so the rings stand out, and (under a microscope) count monthly rings from the last annual ring ('March, April, May, June,...') in to see what month the shell was killed. Dr Nicky Milner at York University did this with Danish Mesolithic oysters for her PhD. The oysters at Sedgeford tend to be found in little piles all over the place or mixed in with other food debris, so I expect that oysters were being brought to the site throughout most of the year. The mussels from the mussel-rich gully were probably brought to the site over only a season. Both these ideas could be tested using the cross-sectioning method.

Hey Soph! I am a bit surprised to be asked to prove something (that there are technologically simple means of preserving shellfish) that I admit is probably archaeologically impossible to detect anyway. I submit as evidence, first, Morecambe Bay's gift to the world (sorry Eric!), the potted shrimp. Secondly, I submit that East End pub staple, cockles pickled in vinegar. Both available in most Waitroses. I also submit as evidence the recipes in Georgiana Hill's 1865 'The Breakfast Book', which contains recipes for potted oysters, pickled cockles, pickled mussels and pickled oysters on pages 96-117. Finally, I submit the techniques for drying, smoking, and salt-fermenting listed in Park et al 1988, 'The culture ofthe Pacific oyster (Crassostrea gigas) in the Republic of Korea', held online by the UN Food and Agriculture Organisation:

http://www.fao.org/docrep/field/003/ab706e/ab706e08.htm

Cooking does draw out a great proportion of the body water, giving a much dryer flesh to preserve by whatever method actually works. As for Saxon un-glazed earthenware being too porous, I agree that there's little chance of their pots being any good at canning in the modern sense. However, they are not neccesarily too porous for long term storage (after all, Roman wine and oil were shipped and stored in amphorae). Even if they were too porous, they could be water-proofed (bees-wax).

So we may not ever know the exact methods employed to preserve shellfish for weeks or months, but it does look practical for the Saxon period.

Hello Dave! I think your problem might be visualising how the measurements I have used relate to the mussel shell, and to each other. So I have attached (I hope) a diagram of a mussel as an adobe document (.pdf). On the left is a diagram of the inside of a mussel valve, and on the right is a cross-section of a mussel at its point of greatest height.

Like all living things a mussel has a front (anterior), rear (posterior), back (dorsal side) and belly (ventral side), although finding these in a mollusc can be tricky, since most do not have faces, spines or tails. So I have included the orientation labels on the diagram.

In the blade-shaped mussels, height is distinctly greater than width, so the cross-section is a pointed oval. The dorsal edge (B in the cross-section diagram) is always more pointed than the other edge (B'), so when shell height is greater than width the mussel is quite blade-like. In the rod-shaped mussels, height is the same or less than width, so the cross-section is round, or even fatter from left to right than it is tall.

Soph - I believe the Chinese dry a great many foods - you can find them in the markets. I Googled "Chinese dried oysters" and came up with a great many hits.

Hello Eve. The report is a work in progress, on the forum here to see what needs to be added, cut and fixed to make it readable to all SHARPies (not just my fellow specialists). Once I have had a few more comments I will re-draft the document incorporating the comments, and I would be glad for you to edit the re-draft. I did of course mean overlie not overly, and 'were' not 'was'. Well spotted.

I have not heard of other AS commemorative deposits, but I am no AS specialist. I myself am only familiar with ditch terminal deposits as votive or commemorative in Iron Age contexts, as endlessly discussed by Hill, curator at the British Museum. Being both a house-husband (and therefore cook, bottle-washer and bin-man) and ordinary guy (and therefore lazy), I favour a more functionalist view that Iron Age depositional patterns are mostly the result of trash being categorised according to percieved risk and then being discarded with minimum effort (everyday stuff just chucked out the door, more noxious stuff like off meat carried further). So I took some convincing to agree that what was found was a commemorative deposit (and am I spelling commemorative right?).

Its clear from the comments so far that you would like more background (such as an explanation of where the measurements were taken, and an explanation of the systematic variation of size and shape with habitat). I tried to keep the report short, thinking that a big thick report would be intimidating. So, a question: do you think our fellow SHARPies would be scared off by a thick specialist report?

Hello Dave! Could you pick out the sentences in the report that you find are pulling you in opposite directions? Then I will try to fix the problem. I did check and convince myself that the differences between the two shapes of mussel weren't due to size or age differences: the rod-shaped mussels have the same distribution of sizes and ages as the blade-shaped mussels. Does that help? Should I explain how I checked?

Hi Greg.
I have only just got access to the forum (been busier than a one legged man in an arse kicking competition). We (Lindsey) both found your lecture and subsequent chats fascinating - seriously.
Thought any more about doing some (funded) work on the global warming front? :)
The answer is in your shells!!
Apparently it was hotter during the time of Plantagenets ......got any shells from back then?

Question about 'Roman' oysters. I remember talking with you (shellfishguy) at Sedgeford during week six, I think it was week 6 anyway. I was the random geezer who asked about the survivability of crab shells in the archaeological record and whether the romans preserved their oysters or not and if so how would they be transported. In about five minutes you had answered all my questions! I have another one relating to your last posting above; do we know (or suspect) that the Romans actively farmed their oysters by 'fattening' them up or that they may have moved them to inland salt pans (brine pools) to keep them fresh.
Thanks, Phil.

Thanks for the clarification on the mussel report and it finally makes sense. I am imtrigued by the fact that different parts of the shore produce different shaped mussels.

Turning now to Roman oysters there were a large quantity found at Fishbourne in 2002 and if I am loking at the correct report the average age was about 5 years. It seems that oysters were much more common them and I wonder if farming is the answer.

Hi Shellfishguy,

Yay Canada! Where are you from? I'm in Toronto. Is England now your home? It's the cost of the flight back and forth that kept me away last summer.
I meant to hold off responding again until I'd reread your report, but I haven't got back to it. Re your question, "Is there too much detail for SHARPies?" - I'd echo Brenda - there isn't too much detail, and we need more reports like these.
I think the fact that the few of us who have read the report here have come back with questions shows that we are interested in - and perhaps need - the details. What you could do is put a summarizing paragraph at the beginning of the report so that those who don't want all the details can get the gist of your results quickly, and then fill out the details for the rest of us.

I'm curious to know - what were the arguments that convinced you that the mussel and bone deposits were the result of a commemorative feast? Like you, I'm generally inclined to think more functionally.

Hello Eve! I am a British Columbian, but have lived in Britain and worked in archaeology since 1986 (the year most people getting their degrees this year were born).

I think it's a commemmorative deposit because

It's spatially very limited with abrupt margins, not gradually tailing off gradually in any direction (which you ould expect if it had accumulated over days or weeks)
it's in an important point in a feature for the feature's spatial definition.
most telling: the mussels are paired and inter-locking, which would not have happened if they had not been buried very quickly.
The mussels have settled into the spaces between the animal bones in the upper part of the animal bone layer, so the length of time between the bones and the mussels ending up in the ditch must have been brief.

I appreciate everybody's comments about detials being 'good'. Thanks Brenda for the idea of a summary paragraph: most articles in academic journals begin with a 250-word abstract summarising the report, so I will write an abstract for the final report.

Dear Phil: You are so right, there is plenty of scope for enthusiatic amateurs to contribute good work in archaeology. For me, marine shells started out as a side-line to my archaeological day-job, and do not feel much more than an enthusiastic amateur even after 10 years. And eventually everybody pauses in the trench, and thinks "Digging through all this dirt, and labelling it, and deciding which colour of dirt came before or after other-coloured dirt, isn't really telling me anything about the people who used to live here". So I gradually abandoned the over-intricate paleo-sedimentology called fieldwork (and 'proper archaeology' by the dirt-obsessed) for retro-economic reconstruction. Just find a class of material or artefact type that appeals aesthetically or intellectually (horn-cores, belt-buckles,spectacles...), and it won't take long for you to end up knowing more than anybody else about them (well, only about a decade).

So be brave Phil, and join us:
shock the old men
and show them again
that stratigraphy's the beginning
and not the aim.

Thanks Greg, if you ever think about standing for prime minister you get my vote!!