In the Stone Age more than 10,000 years ago, ancient humans could turn the ribbons in birch bark into thick black tar. They use this material between oil and asphalt to make tools, such as fixing arrows on arrows and blades on axles. However, up to now, we still can not fully understand how ancient humans did it. However, dental prints found on some black tar blocks indicate that they may be formed by chewing through the mouth, just like chewing gum.
Picture: This chewed birch bark may have been the gum of ancient people, revealing human life in the Stone Age more than 10,000 years ago.
These chewed birch bark tar blocks have become important materials for scientists to study ancient DNA. Two independent research teams published pre-printed papers describing DNA on Scandinavia tar blocks during the Stone Age. The two papers have not yet been peer reviewed, but people are excited about some of the findings they foretell. Its really amazing, says Pontus Skoglund, a paleohuman DNA researcher at the Francis Crick Institute.
Ancient DNA from human bones and teeth has recently revolutionized past research, but over time, many civilizations have not buried the dead or left any remains for analysis. Chewing gum can fill some gaps and reveal a lot of additional information, such as who helped make tools of the Stone Age, what ancient humans ate, and what bacteria lived in their teeth.
The first paper describes three pieces of human DNA left on tar fragments from birch bark 10,000 years ago, all of which were found in a place in Western Sweden called Huseby Klev. Researchers had never extracted DNA from tar blocks before, and the team tried a scheme originally designed to extract DNA from feces, with unexpected success. Each tar seems to have been chewed by only one person. Together, the tar blocks provide DNA from two women and one man.
Where tar blocks are found, raw materials and residues for stone knives are scattered. Therefore, the authors suggest that this is actually a place to make tools. Chewing birch bark tar is a step in the production process. If this is the case, it means that both men and women were involved in making tools in the Stone Age. And because some dental prints seem to come from babiesteeth, this suggests that children also play a role. All this implies the social structure of the Stone Age. Natalija Kashuba, a researcher at the University of Oslo and the first author of the paper, said: The most exciting part is that we are very close to understanding this culture.
Ancient DNA is easily contaminated when modern people process samples. In this case, however, the DNA in chewing gum seems really old. Its clear that the DNA they extracted came from human ancestors who lived between 5,000 and 8,000,000 years ago, and they dont exist anymore, Skolond said. The DNA of the three men looked very much like the DNA of other hunters who lived in northern Europe at the time.
In the second paper, researchers predicted the appearance of a 5,700-year-old woman based on tar patches from chewing birch bark found in Denmark. In the eyes of modern people, she will be very different. She had dark skin and hair, blue eyes, which were typical features of European hunter-gatherers at that time. The recent discovery of Cheddar Man skeleton fossils in Britain shows that he is 10,000 years old, mainly hunting and gathering for a living, with dark skin and blue eyes.
The second team also analyzed non-human DNA in chewing gum. You can find microbial DNA, which opens up other possibilities, said Hannes Schroeder, an ancient DNA researcher at the University of Copenhagen who led the study.
Other research teams have studied ancient dental plaque accumulated on teeth over the years, but gum can instantly reflect substances in the mouth. This is similar to the way scientists study oral microflora today, no wonder, and the types of microorganisms they find are similar. There are only differences between the two microbes, which researchers believe may be due to fewer carbohydrates consumed by hunters before agriculture emerged.
They also found direct evidence of the womans food. The chewed tar contained DNA from wild ducks and eels. This is consistent with archaeological evidence from the site, which includes duck bones and tools for eel capture. In the Stone Age, the place where the woman chewed and spit out birch bark tar was a lagoon. Today, it is the site of a major construction project linking the tunnels of Denmark and Germany.
Theis Jensen, a graduate student with Schroeders research team, helped with pre-construction excavations by persuading colleagues at the Museum Lolland-Falster Museum to hand over a birch bark tar block for testing. Using the DNA, the team has been able to piece together the appearance of a 5,700-year-old woman, what she ate, and even the microbes in her mouth.
Although birch bark tar blocks can answer all the questions, they are still at the core of many mysteries. Making tar blocks requires a stable heating and anaerobic environment. Archaeologists are not sure how Stone Age people did this without pots, or why they chewed chewing gum: for recreation, for health, for tools, or for all of these purposes. But for whatever reason, people chewing birch bark tar unconsciously left a rich historical record.
Source: Liable Editor of Netease Scientist: Qiao Junyi_NBJ11279