thinking about archaeology

Archive for February, 2012

Milestone tagged

The days when staff would arrive at Stonehenge to find someone had painted the stones are gone, but a week ago Tim Daw spotted graffiti on the milestone across the road.This is his photo:

I wrote about this stone earlier, and here is an image I Photoshopped to show the whole stone more clearly, with the original inscription top left which is now below the turf:

And here is how it looks in better times (from wanderingstrays and duncanferg):

There are many of these strung out along the old turnpikes, including this one a mile to the west:

They’re an attractive and curious reminder of past times, and they need a champion.

Books VIII: worms & weathering

Here’s another of my especially prized offprints. It’s a classic and perceptive paper by Richard Atkinson, about how soils form and what that can tell us about archaeological deposits. He had been excavating at Stonehenge during four years before this was published (in 1950, 1953, 1954 and 1956), and was soon to start on the largest trench there in 1958, continuing into 1959, 1964 and 1978. Apart from an early report on the excavation of two Aubrey Holes, this offprint from Antiquity was the nearest he got to actually publishing any of his excavations in peer-reviewed form, but that’s another story.

His letter to Ian Cornwall (the address “Cornwall” was a blend of restrained friendliness and respect) refers to the excavations on which he was about to embark. Cornwall was a sort of all round odd job scientist and bone specialist at the Institute of Archaeology in London.

Filming in Dorset (& reprogramming the TV)

I’m giving you my essential guide to retuning your TV soon, but first a bit of archaeology. This is Maumbury rings, a nice earthworky sort of earthwork near the centre of Dorchester. It looks how it does now because of corporate curation, remodelling during the Civil War and before that as a Roman amphitheatre, but it began as a neolithic henge around 2000BC. The now invisible ditch just inside the bank consisted of a ring of around 50 or so interlocking pits that went down 10m into the chalk. It was partly excavated shortly before the first world war, so really we need to go back and dig some more. Were those pits great empty shafts, as most believe, or could they have held large posts?

I was there yesterday filming for a TV programme, and I was reminded that I should update the Time Team/Mick Aston saga. The public support for both Mick and the TV series (and all the crew, including Mary-Ann Ochota) has been striking. I will be publishing a selection of the many, sometimes quite moving letters I have received in the next British Archaeology. Among the online pieces worth seeing I’ve not noted before are these:

A piece from Mick in the Western Daily Press, that tells about the member of the public stepping in to identify a find (worth reading the whole story):

A brief statement from Mary-Ann, that puts her own spin on the affair:

And this from Mick, defending (quite rightly) the quality of the fieldwork on Time Team:

So I get home from Dorset, and later switch on the TV. No signals. We’ve just had the second round of analogue switch-off. I spent much effort trying to figure it out the first time, and only last night did I get there. Looking for online help, I saw I’m far from the only one who had trouble with this, and curiously many of those struggling with it seem to be people who really know their way around gadgets. If you Google phrases like

i cant find any of my TV channels (25,700,000 results)

how do i find digital channels on my tv? (71,700,000 results)

how do i program my tv for digital? (599,000,000 results)

you get masses of debate, information, gossip and whines, and strikingly most of it seems to lead nowhere useful. It’s not that we weren’t told about the digital switch-over: it’s that we were told too much. Expensive TV adverts, leaflets, press notices, a big website, everywhere for many months, spilling out all sorts of stuff. It certainly got me worried. But I never learned, plain and clear, the simple thing I really needed to know: what to do.

For most of us the TV set is not a piece of technology, but a thing we look at for what it shows us. Many TVs must have been set up by nice delivery men, and the instruction manual (if it’s still around) is long, complex and intimidating. We just watch the thing, we don’t wire it up and re-invent the silicon chip every time we switch on. We want to know how to get BBC1, not what a relay transmitter is or how many sugars the operator needs in his tea.

So if anyone falls on this who hasn’t yet got it sorted, this is what you need to know.

1. The old type of TV signal (analogue) is being switched off so we can move to a new and better one (digital)

2. When that happens, you have to re-program your TV set. That means going back to the beginning, as if you’d just bought it, and telling it to find all the channels. Every set has its own way of doing this, but it’s quite simple. You press “menu”, and select something like “set up” or “installation”, and look for channel selection, retuning or something like that (one of the sets I did actually had a button that said “digital retune”). The key point here is that you want to completely wipe out the old stuff and start again. So you don’t want to find more channels, or update your list: you want to delete all the old channels, and go for factory reset, first installation etc.

3. If none of this seems to work at all, you probably need to buy a new TV.

Stonehenge (noises off)

Sorry, couldn’t resist that one. I wasn’t going to write about this latest piece of Stonehenge silliness, but it’s had so much coverage (and regular readers of this blog might have noticed comments from me in quite a few of the press stories), that I thought I should at least acknowledge it, and perhaps see if there are any lessons.

“Stonehenge mystery may have been solved”, was the predictable cliché of one headline (in the New York Daily News). “Stonehenge was based on a ‘magical’ auditory illusion, says scientist”, is the more informative headline in the Guardian, and most were in this vein: “Was Stonehenge built for sound effects?” (Telegraph), “Was Stonehenge a sound stage?” (Calgary Herald), “Stonehenge design was ‘inspired by sounds’” (BBC News) or “Stonehenge is magic to scientist’s ears” (Sydney Morning Herald).

The clear winner for me, however (among many, many more), was the Daily Mail’s, “Was Stonehenge the result of an extraordinary hallucination after frenzied flute playing?”

Well, it might have been. But was it?

Behind all this, as you’d expect, lay a press release. I haven’t seen it, but the first I heard of the story was a phone call from a British science journalist who told me that someone called Steven Waller was going to address the annual meeting of the AAAS in Vancouver to reveal his acoustic discovery (ie he hadn’t yet given his talk).

The American Association for the Advancement of Science is not known to be an organisation run by eccentric airheads. It’s an influential non-profit body founded in 1848 with an admirable, and necessary, mission to “advance science, engineering, and innovation throughout the world for the benefit of all people” – and it publishes Science, the US equivalent to the British Nature. If you get to address an audience at its annual convention, you have a right to expect to be taken seriously. And science journalists around the world took Steven Waller seriously.

According to his AAAS abstract, he is an “independent scholar” from La Mesa, CA. His talk, “Virtual acoustic images and sound-attenuators as objects of ancient veneration”, was in a session with three speakers organised by David Lubman of the Acoustical Society of America and the Institute of Noise Control Engineering. This posed the same general question as Waller’s paper: Archaeoacoustics: Did Ancient Civilizations Use Acoustic Design To Create Powerful Ritual Spaces?

Waller says that if you walk round in a circle, with two sources of the same sound fixed at its centre a little apart from each other, you will hear the sound rise and fall as you progress. His theory is that neolithic people did this, were extremely puzzled by the effect, and were moved to build Stonehenge as a result: the spaces between the stones in the sarsen circle represent the quieter and louder moments respectively.

Here is a video of the effect of walking around two sources of noise. If you don’t listen too closely, it’s just a noise (don’t have your sound turned up high before you click on this). Or you can download an iTunes file from Waller’s website’s short entry on Interference & Stonehenge. This is clearer (if shorter), but again it is just a noise, if slightly modulating. It does not put me in mind of any structure, let alone Stonehenge.

And perhaps that’s why the drawings created by participants in his experiment – contrary to his claims this past week – don’t look in the least like Stonehenge, if we go by the examples he posted in November last year in connection with an address to the 162nd Acoustical Society of America Meeting, San Diego:

This is the best one, though my five-year-old daughter said it looks like a dog bowl:

He has written much more on rock art at Steven J Waller’s Rock Art Acoustics page, where he lists “hundreds of rock art sites with known sound reflection and/or unusual acoustic properties (tested by SJ Waller unless otherwise indicated)” at sites ranging from “Church Hole (Britain’s newly discovered cave art)” to Hawaii.

I know nothing about sound theory (which perhaps makes me neolithic, in Waller’s view of the world). So I’m not going to address the science, just the simple stuff. Two things jump out at me.

First is Waller’s understanding of human societies. I can sum it up with these quotes from his Stonehenge abstract:

“Sound phenomena perplexed pre-scientific cultures lacking wave theory. Echo myths suggest virtual acoustic images were perceived as supernatural non-corporeal agents… Myths around the world attest to beliefs that echoes were spirit voices calling out from rocks… To people unaware of wave cancellation and reinforcement, the pattern of dead zones alternating with loud zones would have been completely mysterious, hence magical.”

How does he know any of that? He is making deep assumptions, not just about the people who built Stonehenge, but about all people whose culture, to use his language, “lacks” science.

The reality of what he implies is the other way around. That is, the view of the world we take that we define as “scientific” (and that is a view held mostly by specialist scientists, and not the population at large) is a post-enlightenment, historically conditioned perspective. In other words, it is unusual. There are endless ways of experiencing the world around us. A great deal of our own understanding was achieved for us by people long ago who did not benefit from “science” – the wheel, for example, or cooking food. I suggest you would only necessarily find the sound phenomenon that Waller is describing as “completely mysterious, hence magical”, if you had his mindset – if you knew about wave theory, but somehow also you didn’t. You’d be just as likely, for example, to think, hey, that’s a cool effect, I can use that in my music.

Then there is the logic that leads to Stonehenge.

“Acoustic measurements support the hypothesis that ancient rock art locations [prehistoric cave paintings, canyon petroglyphs, megalithic monuments] were deliberately chosen for their sound reflection characteristics, and decorated with images that relate to the echo spirits believed to dwell there… These data support the new theory that sound wave interference patterns were attributed to massive invisible objects, and that this “vision” of a ring of magic stones served as a blueprint for Stonehenge.”

This is circular. The argument seems to be, Here is Stonehenge now, Here is a weird sound effect now, Therefore a weird sound effect caused Stonehenge in 2500BC.

Now you might argue that archaeologists play this game, making up ideas about healing stones, ancestors and midwinter rituals. Yes we do. But there’s a difference. We start with what we know about Stonehenge. This is a great deal, and if Waller had begun there, he would have left his bagpipes at home (the key point being that the one structure he singles out for his theory was far from the first, only or last thing there; the acoustics that work in his lab would not have worked on the site, and the design of Stonehenge did not spring out of nothing). And importantly, we don’t bring in complex science that few of us understand (including, to judge from the press stories, many science journalists) and then ignore everything else.

Books VII: Neil Gunn

A writer I discovered when I was a student in London.

Night at the Museum 2

A chance to give Hoa a quick dust

Last night we finished the job of recording the British Museum’s large Easter Island statue (see here for the first post). As with photogrammetry, the really clever stuff with PTM lies mostly in the software and not the kit. The two most important things here were a shiny little black ball, and a piece of string (the latter was the only thing that gave any grief, when the knots came undone).

James sizes up the statue. Not the largest, but still impressive

James and Hembo took photos for four images of the back, showing separate zones from top to bottom (they finished off the first night by doing this for the hands area at the front). For each one, they set the camera up on a tripod at different heights, from the floor to high on the scaffolding (handy stuff when you’ve got it next door with two nice men to put it all together). Then Hembo took lots of photos while the camera stayed fixed, moving the flash around to alter the lighting angles. The really useful kit here was the wireless trigger that enabled him to fire the camera, which itself tripped the flash. The piece of string ensures the flash is always the same distance from a selected point on the statue, so the light has an even intensity – when the flash was in position, James had to duck out of frame so the shot could be taken. And the black shiny ball reflects back from the flash (creating a specular highlight) so the light direction can be calculated by the software.

Positioning the flash with a piece of string. The camera is on the scaffolding out of shot to the left

A shiny ball at a fixed spot in each PTM image allows the light direction to be calculated

Now comes the slow stuff, as we examine the images and work towards a full description of the carvings, and any damage or dressing marks.

You can read more about the Archaeological Computing Research Group at Southampton here, and here is Graeme’s staff page.

Last night in the Wellcome Gallery

I spent last night all but alone with the British Museum’s Easter Island statue, Hoa Hakananai’a. Graeme Earl, James Miles, Hembo Pagi and I began a project to record and analyse the carving in unprecedented detail. It is one of the British Museum’s most popular objects, but well known as it is, it has been little studied at first hand.

It was taken from the remote Pacific island by the Royal Navy in 1868, and has been on public display in the centre of London for over 130 years, with just two significant breaks. It must be one of the most viewed statues from the island. With around six million visitors a year, the British Museum is the UK’s most popular cultural attraction at which figures are counted (only the smaller and more weathered statue displayed in the lobby of the National Museum of Natural History, Washington DC, which received 7.4m visitors in 2009, is likely to be seen now by more people). By contrast, annual visitors to Rapa Nui, the native name for the island which has a population of some 4,000, are said to have risen in recent years to around 50–70,000.

Alfred Métraux, a Swiss anthropologist who worked on Easter Island in the 1930s, thought Hoa Hakananai’a “without a doubt, the finest example of Easter Island sculpture”, and it has inspired some of our greatest artists, among them Henri Gaudier-Brzeska and Henry Moore. It was selected by Neil MacGregor as one of the 100 objects with which he told the history of the world – and in the same year, it was the target of a protest against BP’s handling of an oil spill in the Gulf of Mexico.

How the statue was found and delivered to Britain is surprisingly well documented, as has been described by Jo Anne Van Tilburg in two BM publications (though the knowledge of the circumstances is particularly frustrating, as the statue was buried in deep stratigraphy that could have told us a great deal, of which there seems to be no record at all). So it is curious how little study there has been of the statue itself. We hope to rectify that by creating detailed digital images that we will make available online. That way anyone with a computer anywhere in the world will be able to see and study the statue and its carvings, and maybe find things that noone else has noticed.

What makes Hoa of special interest is not only its superb preservation, partly down to the unusual use of a hard, basaltic rock, but also the presence of copious carvings on the back. These have always been known about, and photos have been available, but it was only recently since the statute was displayed in the new Great Court, and now in the Wellcome Trust Gallery, that they have been easy for everyone to see.

In conventional histories of the island, most of the statues (of which nearly 1,000 have been counted) were carved in what in an European context would be largely the middle ages (perhaps AD1100–1600). Then mostly later (you might be getting the drift of this chronological point – Easter Island dating is very poorly documented) rocks all over the island were covered in petroglyphs, shallow carvings of birds, animals and abstract or symbolic shapes. This occurred, so the story goes, as part of the development of a different culture that followed social and ecological collapse (as famously described by Jared Diamond).

Hoa was found by the British naval officers in the midst of a veritable gallery of these petroglyphs. It stood near a cliff that falls 300m down to the ocean, and bird colonies that were the focus of historically documented ceremonies. So the statue uniquely embodies these two traditions of art and myth, the statues and the petroglyphs.

Or maybe they weren’t so separate? Critical analysis of the island’s archaeology has suggested to some that Rapa Nui was not colonised as early as is usually claimed. If right, this would make the era of statue carving shorter. That in turn would raise the possibility that the bird cult and the statue cult at least partially overlapped, and were aspects of a single complex of ceremony and belief, perhaps embracing the two key concepts of birth and death.

Hoa Hakananai’a is an inspiring thinking tool for this debate. When we have finished the work we will all be able to see, for the first time, exactly what was carved on his back, and begin to unravel its possible meanings.

We are using two techniques. The simpler is photogrammetry. For this we take photographs of the statue from different directions with an SLR camera (actually two: James took photos from the floor, and Hembo took them from above – around 500 in all). With these we can create precise 3D images of the statue, permitting digital study of its shape and morphological details.

The other technique is called polynomial texture mapping, or PTM (a type of reflectance transformation imaging or RTI). This is really good at enhancing subtle surface variations at fractions of a millimetre, revealing details in objects that are all but impossible to see with the naked eye. It’s perfect for looking at those carvings on Hoa’s back.

It was first applied to antiquities in 2001 – one of the earliest applications of PTM in archaeology was by the British Museum’s own David Saunders in 2004. We take a series of photographs, each lit from a different direction in the dark, and combine them with software into a special type of single image file. On your computer screen or tablet, you can alter the direction and intensity of light at will within this image, and illuminate the carvings from more than one direction at once. Derived from photos, the image shows real colours. But you can also remove this information, so that just the reflected light from the surface shows. Various forms of enhancement can be employed and features can be digitally annotated to enable collaborative study and research of the digital artefact.

Between them Graeme, James and Hembo have more experience of using this technique than any researchers in the UK, and amongst the most worldwide. They recently completed a major AHRC-funded study to trial RTI on many archaeological objects, and they have already worked with the British Museum recording artefacts from stylus tablets to a Fayum portrait.

And this is what they will be doing tonight with Hoa Hakananai’a. By the time we’re finished, this will be the first Easter Island statue to be so fully described.

[The second post is here.]

From left: Graeme Earl, James Miles and Hembo Pagi, members of the Archaeological Computing Research Group, Department of Archaeology, University of Southampton, where Earl is a senior lecturer

Books VI: gallery guides

A random selection of those little guides you are given when you visit special exhibitions

Old Sarum in the snow

I had to visit the museums in Devizes and Salisbury yesterday (hence the cathedral photos), in connection with an exciting little exhibition I’m helping with, as a guest of directors David Dawson and Adrian Green respectively (I earlier referred to British Museum curators as heroic: the challenges they face pale beside those of being responsible for internationally significant collections with such small resources). Going home, I passed a snow-covered Old Sarum with a red sun just falling below the horizon. The light was lovely, but very cold, as it was when I took this photo around midday from the west, the contours of the iron age hillfort and the medieval castle mound in the centre brought out by the dusting of white.

Salisbury Cathedral in the cold