Sequence analyzes complement shovel and brush: Genetic methods have diverse potential in archeology, a study shows. Using genetic traces in sediments, researchers have gained insight into how prehistoric people used the flora of their homeland. About 30,000 years ago, the inhabitants of a cave in modern-day Armenia apparently used a wide range of plants for different purposes: they could have served as food, as medicine or as a source of fiber for yarn.
Eleven meters deep and 18 meters wide, it once offered protection from wind and weather to prehistoric hunters and gatherers of the Palaeolithic Age: In the Aghitu-3 cave in the highlands of southern Armenia, archaeologists have discovered numerous traces of human settlement dating from around 39,000 to 24,000 years ago years. “Stone artefacts, remains of animals, bones, tools, shell beads and charcoal from campfires have already been found in the sediments,” says excavation leader Andrew Kandel from the University of Tübingen. However, there are hardly any tangible traces of one aspect that the team is interested in: “Although we know that plants played a fundamental role in the life of prehistoric people not only as food, parts of plants such as seeds, leaves, fruits and roots remain – because they are organic and usually decompose quickly – are rarely preserved and thus make research difficult for us,” says the scientist.
Searching for genetic traces in sediments
In order to be able to shed light on these secrets of the Stone Age environment, Kandel and his colleagues turned to a method that is increasingly finding its way into archaeology: traces of DNA in sediments can provide evidence of creatures that once lived in caves – or were taken there. For this purpose, the sequence sections found are compared with reference databases using the method of so-called DNA metabarcoding. In this way they can be assigned to known species or at least groups. For their study, the scientists specifically searched for traces of plant DNA in the layered system of the cave sediments.
First of all, the results showed that in times when there were traces of human use of the cave, a comparatively large amount of plant genetic material was found in the sediments. The researchers therefore attribute most of the plant traces found to the activities of the Stone Age inhabitants: the people probably collected the plants and carried them into the cave to be used, so the assumption. “After use, they then left the plant remains in the cave and the DNA remained – to our delight – preserved in the sediments,” explains co-author Angela Bruch from the Senckenberg Research Institute and Natural History Museum in Frankfurt am Main.
Plants with utilization potential
Using the method of DNA metabarcoding, the researchers were then able to obtain information about which plants were brought into the cave. In total, they identified traces of representatives from 43 families. What is remarkable is that almost all of them are known to have potential uses by humans. Some of the plants can be used as food, while others have medicinal properties or can be used as flavorings or even mosquito repellents, the researchers report. Findings of DNA from plants, which can provide dyes or fibers, also suggest that people in this region used plants to make sewing thread or cord and to thread shell beads. “These findings fit into the overall picture of ‘Aghitu-3’ like a missing piece of the puzzle. Because in the cave, needles made of animal bones were also found during our excavations. We now know with a high degree of probability that the people in the cave sewed and how they did it,” says Kandel.
As the scientists conclude, their study could now also have a pioneering character: it is becoming apparent that the analysis of plant DNA from sediments represents a promising new tool for studying human behavior in prehistoric times. “In the future we want to use the method at other sites to find out more about our ancestors,” says Bruch.
Source: Senckenberg Research Institute and Natural History Museums, specialist article: Journal of Human Evolution, doi: 10.1016/j.jhevol.2022.103258