Past lives caught in the dust of trees

Standard I’m cur­rently work­ing at the Annals of Botany to help out with their social media side. There’s a bit more to it than subtly drop­ping links to their site, like this one. At the moment I’m strug­gling with the Facebook integ­ra­tion, but there’s a fun side too. I wouldn’t have browsed AoB if I’d not been hired, and that means I would have missed out on papers like Phytoliths in woody plants from the Miombo wood­lands of Mozambique by Julio Mercader and his team at Calgary. I’ll admit the art­icle title doesn’t say much to the lay­man, but it’s actu­ally some­thing deeply cool that I didn’t find out about till my MPhil.

If mega­liths are big stones and micro­liths are small stones like arrow­heads, then phyto­liths are clearly phyto-stones. Phyto– in this case mean­ing plant.

Phytoliths are micro­scopic stones formed in some plants. When a plant’s roots draw up water they also draw up the min­er­als dis­solved within it. In the case of the silica this gets pulled out of the water and depos­ited either in the cells or between the cells. The exact shape of the phyto­liths var­ies on the part of the plant the silica is depos­ited in, the avail­ab­il­ity of silica and, most excit­ingly for archae­olo­gists, the spe­cies of the plant.

Phytoliths are use­ful because nor­mally bio­lo­gical mater­ial doesn’t hang around long in the soil. Once some­thing is dead it’s lunch for some­thing else. Phytoliths are bio­lo­gical mater­ial but not organic, so they don’t break down in the same way. Mercader et al. are clear that’s is not an unam­bigu­ous relal­tion­ship. Time still has an effect, but it’s easier to find phyto­liths than it is to find organic remains for plants. Still as use­ful as they are, phyto­liths alone are not enough. A hand­ful of phyto­liths under a micro­scope would just look like a nobbly (or smoothish) thing. If you haven’t seen what a baobab phyto­lith looks like, you’re not likely to guess from simply look­ing at the phyto­lith and this is where Mercader et al step in.

Elephants in Miombo woodland. Photo by Jussi Mononen.

Elephants in Miombo wood­land. Photo by Jussi Mononen.

If you’re inter­ested in study­ing the palaeoe­co­logy of Africa in the past you’ve been rel­at­ively lim­ited to north of the equator. Mercader spot­ted that the biggest phyto­chor­ion (plant eco­sys­tem) south of the Sahara is the Miombo wood­lands. It’s huge. It runs from Angola and Namibia in the west to Mozambique in the east and from the Tanzanian shores of Lake Victoria in the north to Botswana and South Africa in the south. The dom­in­ant tree is Miombo, hence the name, which refers to a num­ber of trees of the same genus, but with dif­fer­ent spe­cies. Obviously it’s a cru­cial zone for under­stand­ing the eco­logy of sub-Saharan Africa, but no-one has described the phyto­liths of the region.

Miombos Botanical Transect after Mercader et al.

The area stud­ied was a tran­sect through the forest between the Lake Niassa shore at Metangula and the high­lands at Njawala, a dis­tance of 50km and a rise from 465m above sea-level to 1841 above sea-level. They also used indi­gen­ous col­lect­ors to sample the flora in a 5km radius around Metangula and Njawala. They estim­ate they got over 90% of the spe­cies used by the nat­ive peoples. Given that a lot of usage is likely to be dom­in­ated by rel­at­ively few spe­cies, that’s a lot of plant mater­ial. There’s then a LOT of list­ing and descrip­tion of phytoliths.

The com­mon fea­ture that amazes me is how small many of these phyto­liths are. Some are just 20–40 μm long. A micro­metre (μm) is one thou­sandth of a mil­li­metre. Despite this Mercader et al, point to the phyto­liths at the other end of the scale, some are around 200μm in length and over half are over 50μm. This means if you use stand­ard tech­niques to sieve for phyto­liths using a 50.238 to 63.246μm cut-off, you’ll miss all these lar­ger phyto­liths. That’s going to mat­ter if what you want to find evid­ence of a ‘Zambezian’ forest at an archae­olo­gical site.

It’s the sort of sci­ence that is easy to over­look. The authors don’t con­clude that whole text­books need to be re-written or that our under­stand­ing of Africa’s past has to be rebuilt from scratch. It’s also the kind of sci­ence that’s easy to whine about. Here they are, pick­ing flowers to exam­ine tiny stones in the stems rather than just appre­ci­at­ing the beauty.

But it’s also the kind of sci­ence that increases the amount of beauty and mys­tery in the world.

Until I took my MPhil, I was com­pletely ignor­ant of phyto­liths. I could view the same plants an archaeo­bot­an­ist, but saw a lot less. Before I read this paper I didn’t know that that the Miobos wood­lands were unex­amined. Knowing that these things are out there opens up new pos­sib­il­it­ies for what can be done. At Çatal­höyük they’re examin­ing phyto­liths left behind in what are almost shad­ows of woven bas­kets to flesh out details of human life in the past. In the case of this paper, it provides a bench­mark for meas­ur­ing future study­ing against. It’s detailed, metic­u­lous and some­times opaque to the non-specialist, but it’s also a descrip­tion with last­ing value. Currently pub­lic­a­tions are often judged on cita­tions garnered over a few years. That misses the value of this paper as it will be import­ant for dec­ades. Indeed, if this eco­sys­tem sud­denly becomes a tar­get for eco­nomic devel­op­ment it could even be import­ant for cen­tur­ies as a snap­shot of the cur­rent state of the Miombos woodlands.

If you want to see the phyto­liths they found, you can down­load the paper for free.

ResearchBlogging.orgMercader, J., Bennett, T., Esselmont, C., Simpson, S., & Walde, D. (2009). Phytoliths in woody plants from the Miombo wood­lands of Mozambique Annals of Botany, 104 (1), 91–113 DOI: 10.1093/aob/mcp097

Photo credit: Elephants in Miombo wood­land. Photo by Jussi Mononen.

Do we need an Industrial Archaeology?

Cromford Canal

Cromford Canal. Click for lar­ger image.

It’s easy to take a World Heritage Site for gran­ted when it’s on your door­step. I had thought of shoot­ing a short port­fo­lio of Cromford for a com­pet­i­tion. They required ten pho­tos. After look­ing into the pro­ject I’ve decided that the com­pet­i­tion isn’t going to hap­pen for me, but a short photo essay on Cromford, or pos­sibly the Derwent Valley Mills, remains an inter­est­ing idea.

Industrial Archaeology can get short shrift from other archae­olo­gists. Often there’s writ­ten records, plans and for some places oral accounts of work at a site. Is Archaeology neces­sary? Mark Henshaw, the Archaeology Dude, makes a good argu­ment that Archaeology can draw mul­tiple lines of evid­ence to inform his­tor­ies of the past. I wouldn’t dis­count that, and I think his point, Archaeology isn’t just about dig­ging, is very import­ant from an American per­spect­ive because there Archaeology is seen as a branch of Anthropology. In the UK you’re more likely to see Archaeology paired with History or Classics. So do we really need Industrial Archaeologists when there so many Early Modern Historians.

I think another factor Archaeology brings is spa­tial think­ing. Looking at the early days of the pro­fes­sion­al­isa­tion of Archaeology in Britain, one of the fea­tures is an attempt to dis­tin­guish Archaeology from History by tak­ing on ideas of Geography. People like OGS Crawford were keen to emphas­ise that Archaeology stud­ied human activ­it­ies in space as well as time. Again, in the UK, when Processualism was tak­ing off in the USA, the British aca­dem­ics took inspir­a­tion from it, but also from the ‘New’ Geography.

The Manager's House, Cromford.

The Manager’s House, Cromford.

Applying this prac­tic­ally, it’s easy to say what the pos­i­tion­ing of the Factory Manager’s house, oppos­ite the main gate of Arkwright’s Mill at Cromford, means by its loc­a­tion. There are other more subtle ques­tions though. What did draw­ing a second water chan­nel through the Derwent Valley mean for land use and access­ib­il­ity? Why was Willersley Castle, a grand house that Arkwright built for him­self, placed where it was? How did it relate to the church he built? If you want to know why a mill owner would want to build a church for his work­ers then, as Mark Henshaw says, you have to look at his­tor­ical records too.

You can write a his­tory purely from his­tor­ical records and archives, but if you want to exam­ine the human exper­i­ence, espe­cially of humans that weren’t writ­ing much, then an Industrial Archaeology can yield a richer, more four-dimensional exper­i­ence, than Anthropology or History alone.

What does the new henge mean for Stonehenge?

Confusion at Stonehenge
Confusion at Stonehenge

Confusion at Stonehenge

I don’t know.

I think the cov­er­age at places like the BBC are good, David Gregory found it excit­ing and I thought his story was a good read. However there are too many details miss­ing from the reports to come to any con­clu­sions. That’s not a com­plaint about the cov­er­age, the mass-media isn’t an archae­olo­gical journal. It’s not even a gripe about pub­lic­a­tion by press-release because Mike Parker Pearson showed last year that news leaks out, so why not give the brief details out properly?

On the other hand the Birmingham team are look­ing at the land­scape and, from read­ing the reports, I’ve no idea where this new site is in rela­tion to Stonehenge. It’s almost cer­tainly in sight of Stonehenge, but then the land­scape round there is littered with bar­rows, Bronze Age burial mounds. The loc­a­tion will affect how we see the land­scape. This henge isn’t to be con­fused with Bluestonehenge, the site found by the river Avon near Stonehenge last year. It’s also not Woodhenge, des­pite being made of wood, because that’s a dif­fer­ent site near Durrington Walls, which is another site that has been in the news in recent years.

There’s not a lot I can say about the astro­nomy of this henge either. It could be aligned to the sum­mer sun­rise, but I can’t tell because the dia­gram doesn’t say which way north is. Also look­ing at the dia­grams, the stone circle seems to have entrances facing one axis and the tim­ber circle an entirely dif­fer­ent align­ment. In fact, the entrance to the wooden circle seems to be facing stones. To me, that sug­gests at least two phases to the monu­ment. I ima­gine that there’ll be some sort of test excav­a­tion along sim­ilar lines. If you want to take your time plan­ning an excav­a­tion it’s a very sens­ible idea not to flag up the loc­a­tion in the news.

Ground Penetrating Radar by Ben Urmston

Ground Penetrating Radar by Ben Urmston

The con­fu­sion that this find­ing is going to cause will be huge fun for Stonehenge watch­ers. The equip­ment they’re using is Ground-penetrating RADAR. This used to be rub­bish, some­thing you’d only use in an urban loc­a­tion where you got a good sig­nal, but as with everything involving a micro­pro­cessor it’s advanced massively. It means that there’s huge swathes of land where some com­pletely unex­pec­ted things will be found. In some­where as busy as the Stonehenge land­scape there has to be much more than this wait­ing to be dis­covered. It’ll raise some awk­ward ques­tions for archae­oastro­nomers, because des­pite there being align­ments will these newly dis­covered struc­tures have blocked the view?

The excit­ing thing about this work is that it shows not only to we not have all the answers, we don’t even have all the questions.

Photo credit: Ground Penetrating Radar photo by Ben Urmston.

Survey: How do you know you’re doing it right?


Archaeological sur­veys tend to be samples of a site. How do you know you’re doing it right when you can’t see the arte­facts you’ve missed? Couldn’t you be miss­ing large chunks of inform­a­tion because it’s not what you’re expect­ing to see? David Pettigrew guest blogs at The Archaeology of the Mediterranean World,

Astronomy at Ston̈ehen̈ge for the 2010 Summer Solstice


I’ve been busy, recently and I’m likely to stay that way for a while, hence the lack of posts. Still, I’m hop­ing to be able to take a trip to Stonehenge this year to see the sol­stice. That’s why my pre­dic­tion is that it will be cold and wet and thick cloud will pre­vent any­thing inter­est­ing mak­ing an appear­ance. However, if there are clear skies, there could be plenty to see over Stonehenge this sol­stice.

Natural Astronomy

There’ll be plenty to see in the even­ing sky after sun­set at 9.26pm. To the west Venus will be extremely bright at mag­nitude –4.0 (the lower the num­ber the brighter some­thing is). When you see it you won’t be able to mis­take it for any­thing else. That will be set­ting at a quarter to mid­night, so there’ll be plenty of time to see it.

Stonehenge astronomical chart for sunset solstice 2010

Position of the plan­ets at sun­set. Click for full size.

Moving to the left, are Mars, Saturn and the Moon. Mars will be mag­nitude 1.3 so it won’t be the bright­est thing in the sky, Arcturus and Vega will be brighter but it’ll still be easy to find. If you’re strug­gling find the Plough. The two pointer stars that point up to the Pole Star will be more or less also point­ing down to Mars this even­ing. Mars sets at a quarter to one, but if you want to see it real­ist­ic­ally you’ll have to be look­ing before mid­night. If you’re lucky it’ll have a slight ruddy glow. Saturn will be the only bright object between Mars and the Moon. In fact it’ll be slightly brighter than Mars in per­fect atmo­spheric con­di­tions, but I doubt my eyes will be good enough to meas­ure that.

The Moon will be in Virgo, near the star Spica, which was thought to be a sheaf of corn in the hand of Ceres, if you’re Roman, or Demeter, if you’re Greek. Fans of myth­o­logy will be keenly aware that Demeter/Ceres had a daugh­ter with Zeus which makes her not tech­nic­ally a vir­gin, but the Greeks called her Parthenos and that usu­ally gets trans­lated as vir­gin. To find Spica usu­ally you’d fol­low the arc of the handle of the Plough to Arcturus, and then Spica is the next bright star down. This night it’ll be the closest bright star to the Moon. It could be hard to spot because the Moon will be bright. It’ll be 69% lit, nine days old and wax­ing gib­bous. It’ll be more or less low in the sky to the south at sun­set and set around 1am, which is astro­nom­ical mid­night. It’s not the same as civil mid­night because these days Stonehenge is on Daylight Saving Time, like the rest of the UK.

Stonehenge astronomical chart for midnight solstice 2010

Stars at 1am over Stonehenge. Click for full size.

Around 1.20am Jupiter rises. It’s likely that you’ll need to wait till 2am to get a good view. It’ll be shin­ing in sil­ver at mag­nitude –2.4 and, because Venus will have set, it’ll be the bright­est planet on the sky. Jupiter will have a part­ner, but it’s highly unlikely you’ll see it at Stonehenge. Uranus will be close to Jupiter. If you hold out your hand at arm’s length then Uranus will be five or six little fin­ger­nail widths to the right of Jupiter. Normally there’s no chance at all of see­ing Uranus, but at the moment it’s at mag­nitude 5.8 which puts it right on the limit of human vis­ion. If you have very good eye­sight and the atmo­spheric con­di­tions are per­fect you’ll see what looks like a very faint star next to Jupiter, and that’s Uranus. But even if we have that, I still doubt you’ll see it.

The reason is that it takes time for your eyes to adapt to the dark. Ian Musgrave says it takes a few minutes to see down to mag­nitude 5 or 6. Your eyes need to build up chem­ic­als to make them more sens­it­ive. Every time you see a bright light, like car head­lights from the nearby roads, torches from other vis­it­ors who — quite reas­on­ably — don’t want to break their necks walk­ing around and any light­ing from English Heritage this adapt­a­tion will be lost. On top of this there’s light pol­lu­tion. We don’t just use energy light­ing streets. A lot of energy is used to light up the sky, for no obvi­ous reason. This reflects from any water droplets in the atmo­sphere and gives a sodium glow to the sky. Even cit­ies over the hori­zon will be vis­ible by their light pol­lu­tion and this will pre­vent you from see­ing some of the stars. You’ll stand a bet­ter chance of see­ing Uranus if you use binoculars.

There is another difficult-to-spot object in the sky. To the north near Capella is Comet McNaught. Searching on the web for this is no help. There’s a lot of Comet McNaughts because Robert McNaught has found over fifty of them. This one is Comet McNaught 2009 R1. The cur­rent fig­ures I have are that it will be between mag­nitudes 5 and 6. If that’s the case then you might not see much without dark-adapted eyes and it’s a bin­ocu­lar object. This fig­ure is uncer­tain though because the comet is get­ting closer to the Sun. Around June 30-ish it’s pre­dicted to be as bright as mag­nitude 2. Capella is not too hard to find. It’s the only bright star above the north­ern hori­zon, and it will be due north around half-past mid­night. The comet will be a couple of degrees above it. Look for a fuzzy star.

The Sun is due to return a few seconds before 4.52am. Again, day­light sav­ing explains why the Sun sets less than three hours before mid­night, but doesn’t rise till almost five hours after.


Or, if you don’t tell your friends what they are, UFOs.

The big events will be the passes of the International Space Station. There’ll be two and half over Stonehenge. The first will be at 1.08am till 1.10am. You’ll be able to see the ISS drop­ping from 38º up in the sky to the south­east down to the hori­zon. It’ll be bright (mag­nitude –2.7) but it will also be fast. This is the half appear­ance and you may not see it. You best chance is to be look­ing at Aquila, the bright­est star in the south­east at this time, and it should appear near there.

The next appear­ance is the best. At 2.40am it will rise in the west and pass over­head before set­ting in the east at 2.46am. It will look like Venus did, but it will vis­ibly be mov­ing across the sky. It could look like an aero­plane and if any­one else says that you might want to agree before point­ing out that there’s no vis­ible flash­ing lights like there would be on an aero­plane. It will also be trav­el­ling too fast. Get your friends to rule out other obvi­ous causes like Chinese lan­terns, reflec­tions of head­lights, plan­ets and so on so that you sound like you’ve been reluct­antly con­vinced that whatever you saw was not of this world.

Then at 4.15am you can make every­one jump out of their skin by yelling “They’re BACK!” when the ISS makes another pass from the west again. This time it will set 4.23am in the eastsoutheast.

For extra UFO points you can also try point­ing out an Iridium flare. This is a sud­den bright reflec­tion from one of the Iridium com­mu­nic­a­tions satel­lites. There are two dur­ing the course of the night. At 10.52:44pm on June 20 there’s a mag­nitude –1 flare west­north­w­est above a hand­span above the hori­zon. At 3.22:06am there’s a brighter mag­nitude –4 flare in the east­south­east. These will be fast; they’ll last for just a few seconds.

Flare Simulation. Source: Wikimedia Commons

Heavens Above, where I got these details from for the ISS and Iridium also has some transit times for fainter satel­lites, but the night sky is littered with satel­lites. If you see any­thing that looks star-like mov­ing across the sky over six-eight minutes then it’s quite pos­sibly a satel­lite. Some of these could be mis­taken for aero­planes. Registering on the site will enable you to print off your own star charts for ISS and satel­lite passes. If you’re on twit­ter @twisst can tell you when the ISS is passing over your loc­a­tion and send you alerts.

If you’re inter­ested in vis­it­ing Stonehenge for the sol­stice this year and want more prac­tical advice, like remem­ber­ing to pack toi­let roll, you’ll find Heritage Key help­ful. And if there are clouds, it might not all be bad news.

Blogging Archaeology at the SAA


Colleen Morgan has put for­ward a pro­posal for a Blogging Archaeology ses­sion at the SAA con­fer­ence. My con­cern was that an explict blog­ging ses­sion would be case of preach­ing to the choir. Technophobes would have the con­veni­ence of skip­ping all the awk­ward talks in one pack­age. However I think she’s proven me wrong. I think she’s got some use­ful ideas that could bene­fit from a con­fer­ence ses­sion, in par­tic­u­lar thoughts on pri­vacy. I think this is a poten­tial head­ache, espe­cially if courses are going to encour­age stu­dents to blog. It could be use­ful to help dis­tin­guish between anonym­ity and pseud­onym­ity, and a con­fer­ence might be the place to tackle this kind of ques­tion head on.

Sadly I don’t anti­cip­ate attend­ing the SAA con­fer­ence, but if there’s one ses­sion that will break out bey­ond the con­fer­ence, then you’d expect it to be the one about blog­ging. You should keep an eye on Colleen’s blog Middle Savagery for more devel­op­ments, but really Colleen is full enough of inter­est­ing ideas that you should be read­ing her blog anyway.