A digression this morning to pollen analysis. The trail starts at reference 1, where Stewart-Moffit writes about the order in which trees arrived in north eastern Scotland after the ice retreated 12,000 years ago or so: ‘… Birch (betula) first appeared с. 9500 BC with Hazel (corylus) с. 8050 BC; they were followed shortly after by broadleaved trees such as Elm (ulmus) c. 7550 BC and Oak (quercus) c. 6550 BC with Ash (fraxinus) and Alder (alnus) by c. 6150 BC. Scots Pine (pinus sylvestris) could also be found at higher altitudes as shown on Map 2.1…’.
This took me to reference 2 which goes into rather more detail about how this is done, with pollen.
Lots of material about pollen analysis on the Internet, where I am also told about various standard texts, which seem expensive. But I guess the offer of the text at reference 3 snapped above is an aberration or a mistake: one sometimes gets odd prices in Internet marketplaces. But there are the encyclopedia entries at references 4 and 5 - and for those of a historical bent there is reference 6.
This all works because pollen grains come in all kinds of bizarre shapes and, up to a point anyway, one can identify a plant - say down to the level of a family of plants - by its pollen. Furthermore, pollen lasts a long time and one can still identify very old pollen in this way, even fossilised pollen.
So if one can find a stratified source of pollen which one can date by other means, one is away. It seems that cores taken from the sediments at the bottom of lakes or from old beds of peat are good sources in the present context.
[Coire Ardair, north of Loch Laggan, was occupied by a valley glacier during the Loch Lomond Stadial. Its maximum extent is constrained by the moraines in the valley bottom. Photo: B. Davies]
One then samples the core in some appropriate way, separates out the pollen, samples that again, and then peers at individual grains through a microscope and identify it. If one does enough of this, one can plot the relative frequency of pollen grains of the species of interest over time, say over the past 12,000 years, that is to say after the Loch Lomond Stadial (of reference 7). Which is all fine and good when you reduce it to the sort of summary I started with above - but it all looks to depend on a great deal of skilled but grunt work (by students?) and quite a lot of assumptions about pollen production and dispersal.
Dispersal by wind that is. The method does not work very well for the much smaller volumes of pollen dispersed by insects.
Lakes and bogs good because the pollen does not move about much once it has landed. Streams bad.
Extraction of pollen grains from the sample is likely to involve filters (for size), acid baths and alkali baths. It seems that, with care, the pollen grains can stand up to all this.
In order to profile a single sample, the researcher might need to look at and identify as many as a thousand pollen grains. Which presumably amounts to a lot of quality time peering down a microscope. Slow work until one has committed the shapes of the common pollen grains to memory.
A simple pollen diagram. Probably fictitious. And now the tricky work of interpretation can start!
One of the problems being that while hazel nuts were important in the Stone Age economy in Scotland, the pollen of the hazel cannot be distinguished from that of the bog myrtle - a plant which likes peat bogs and which is well-liked by beavers. Parts of the plant are sometimes used as a flavouring - but not as a food.
Conclusions
An entertainment for a dull Monday. But there are lot of people who take it much more seriously, for their living.
PS 1: I have just taken delivery of a nice, but very small, hardback edition of 'Much Ado about Nothing' from 1953. Which originally cost what I thought was the surprisingly large sum of 15/-. The Cambridge edition, the heritage Arden edition seemingly having vanished from the shelves. Against a forthcoming visit to the Theatre Royal, to see the chap that I remember from 'The Night Manager'. BH will use a text from the other place, that is to say from Oxford.
PS 2: some time later, I started to wonder whether the complex shape of the pollen grain had anything to do with it knowing it had landed at the right place, on the right place on the stigma of the right sort of plant. A thought probably inspired by remembering vaguely about Van der Waals’ forces between compatible complex molecules. Gemini said up to a point, but not in the way of a lock and key. And in the time available I only found papers which talked of adhesion at the level of individual proteins, rather than at the level of geometry. One more thing to turn over in slow time.
References
Reference 1: The Circular Archetype in Microcosm: The Carved Stone Balls of Late Neolithic Scotland - Chris L. Stewart-Moffitt – 2022.
Reference 2: The form and fate of Scotland's woodlands – Richard Tipping – 1994.
Reference 3: Pollen Analysis – Moore, P., Webb, J., & Collinson, M. – 1991.
Reference 4: https://en.wikipedia.org/wiki/Palynology.
Reference 5: Pollen Analysis - Margaret Kneller - 2009. In Encyclopedia of Paleoclimatology and Ancient Environments in Encyclopedia of Earth Sciences Series from Springer. Via ResearchGate. A bit easier going than reference 4.
Reference 6: One hundred years of Quaternary pollen analysis 1916-2016 - H John B Birks, Björn E Berglund - 2018.
Reference 8: Much Ado about Nothing - Sir Athur Quiller-Couch, John Dover Wilson (editors) - 1923, 1953.
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