Scientists in Denmark have been able to extract a complete human DNA sample from a piece of birch bark pitch that is dated to more than 5,000 years ago, according to a report in December 2019. Apparently, it was chewed upon (as a kind of chewing gum). This was the first time that an entire ancient human genome has been extracted from anything other than human bones.
They found the sample during an archaeological dig at Syltholm, southern Denmark, where the materials found were covered in mud, which indicates a high level of preservation of organic remains.
A study of the birch pitch by the University of Copenhagen has provided information on the gender of the person who chewed it, what she had last eaten and the germs in her mouth. Researchers have gone to the extent of saying that probably the woman had dark hair, dark skin and blue eyes! Moreover, genetically, she had a closer link to people from the mainland Europe than to those living in central Scandinavia at the time. But they have not been able to find out why their subject chewed the bark: whether to turn it into a kind of glue, to clean her teeth or to stave off hunger.
The study was published in the review Nature Communications.
The researchers also recovered traces of plant and animal DNA—hazelnut and duck—confirming what archaeologists already know about the people who lived there at the time.
Earlier, in May 2019, a study reported that DNA derived from ancient masticated lumps of birch bark pitch (referred to as ancient chewing gum) found at Huseby-Klev, an early Mesolithic site on the Swedish west coast, pertain to two females and one male, who were perhaps among the first people to settle in Scandinavia more than 10,000 years ago. The study conducted at Stockholm University and published in Communications Biology stated that few human bones of this age have been found in Scandinavia, and not all of them have preserved enough DNA for archaeogenetic studies. The DNA from the chewing gums was the oldest human DNA ever sequenced from this region.
The pieces from Huseby-Klev were a result of excavations done long back—in the early 1990s. But it was not possible to analyse ancient human DNA at the time, let alone DNA embedded in non-human materials. So the pieces were stored. Researchers say that the masticates made out of birch bark tar were used as glue in tool production and other types of technology during the Stone Age. But then why they are considered ‘chewing gums, (chewed by people) is not clear.
Gum material chewed upon by people in earlier times is considered an alternative source for human DNA, in place of human bones, in archaeogenetic studies.
The study at the Archaeological Research Laboratory at Stockholm University stated that the individuals shared close genetic affinity to other populations in Sweden and to early Mesolithic populations from Ice Age Europe of the time. So, the genetic composition of the Huseby Klev remains show more similarity to western European populations than eastern ones. However, the tools produced at the site were a part of lithic technology brought to Scandinavia from the East European Plain, i.e., what is Russia today. This idea of a culture and genetic influx into Scandinavia from two routes had been proposed in earlier studies. So the gum samples provide a link directly between the tools and materials used and human genetics. According to the researchers, they can not only help in tracing the origin and movement of peoples long time ago, but also provide insights in their social relations, diseases and food.
The study was published in Communications Biology.