Pollen for historical research

How did people live 6,000 years ago? What did they grow, what was the climate like? This is being investigated by the Institute of Prehistoric and Protohistoric Archaeology – with the aid of, among other things, pollen samples. In the great collection of comparative samples, these samples are also used to train students.

Achoo! They are microscopically small and cause sneezing fits or streaming eyes among allergy sufferers. We are talking about pollen. From mid-January to October, pollen grains fly through the air or are transported by insects from bloom to bloom to pollinate trees, grasses, cereals, fruit and other plants. They are real survivalists: pollen grains are extremely robust – thanks to their solid shell, which protects the sensitive genetic material from UV radiation. They are so robust that they can also be found and examined in layers of soil that are metres deep (from prehistoric and protohistoric times). This is precisely what makes pollen so special to Prehistoric and Historic Archaeology: "Through pollen and its occurrence in the soil, we know how people lived 6,000 years ago," explained archaeobotanist Dr Walter Dörfler, who analyses the pollen. Among other things, Dörfler is responsible for the complete collection of comparative samples and the smaller teaching collection used for research and training students at the Institute of Prehistoric and Protohistoric Archaeology.

Difficult identification

Archaeobotanist Dr Fritz-Rudolf Averdieck began collecting samples in the 1960s. "We now have around 6,750 preparations of 161 plant families at the Institute and we can use them to demonstrate the occurrence of pollen on the North German Plain and, to a smaller extent, the Mediterranean region," said Dörfler, who is repeatedly impressed by the diversity of the findings supplied by pollen during soil analysis. "We take a sample from a long core of soil, we extract 10 to 120 micrometre big pollen grains (editor's note: 100 micrometres is equivalent to 1/10 of a millimetre) in several stages in the lab, we count and examine them under a light microscope." One of the tasks here is to identify the family, genus and species of pollen. What is simple with a hazelnut bush (species: hazelnut bush – genus: hazel – family: birch) does not work with all samples: "Many of the pollen grains are so similar that it is only possible to discern the family or at best the genus. For example, while the genetic material of local oak species is different, the pollen looks completely identical."

The scientists consult the comparative collection to be sure they have the right plant family for the pollen. Captured on nearly 7,000 specimen slides are the most diverse species and kinds of pollen: round, oval or wreathlike pollen grains with a smooth surface (wind pollinated), with spikes (insect pollinated) or air-filled sacs (pine trees), with slits, pores and holes (apertures) whose number and arrangement are important for identification. "The collection allows us to look at the pollen grains from all sides in 3D and at their composition." The more clearly the pollen can be identified, the more exact the results of the research.

Contemporary botanical witnesses

If pollen analysis was originally introduced to examine the relationships between plant species in botany, science is now taking it a few steps further: "Thanks to the investigations, we can trace what people grew and ate a long time ago, whether they traded, whether their surroundings were forest, meadow or fields, what the climate was like and so much more," said Dörfler. Evidence of changes can be found, too, whether that was a volcanic eruption or clearing of forests to build settlements. Science knows, for example, that hemp did not become an important cultural plant for fibre production in the north until 800 years ago and the beech only become more widespread around 2,000 years ago. In conjunction with other sciences like history or geology, pollen also assists with the discovery of important findings for reconstructing people’s living conditions. "Pollen analysis and its results are really very fascinating," said Dörfler. So fascinating that the archaeobotanist, who himself suffers from hay fever, is happy to forgive pollen grains for the occasional sneezing fit in spring.

Author: Jennifer Ruske