Did It Keep Its Flavor? Stone-Age ‘Chewing Gum’ Yields Human DNA

The artist Viktor Mikhailovich Vasnetsov published this imaginative depiction of the Stone Age between 1882 and 1885. (Image via Wikipedia)

(CN) – An ancient piece of chewed-up birch pitch tar has given scientists a glimpse into the entire genome of a 5,700-year-old human from what is now Denmark.

Thanks to the advanced technology allowing scientists to recover ancient genomes, a team of archaeologists have essentially built a complete profile on an individual who lived thousands of years ago. Through analysis of the contents from this piece of birch pitch, the team found plant, animal and microorganism DNA that provide insights into the oral microbiome and potential sources of the individual’s diet.

The team published the findings Tuesday in the journal Nature Communications.

A chewed piece of birch pitch and its find location at the site of Syltholm on the island of Lolland, Denmark. (Nature Communications)

Birch pitch is a thick, black substance obtained through the heating of birch tree bark. It has been used, among other things, as an adhesive since the Middle Pleistocene time period, approximately 760,000 to 126,000 years ago.

It was used to mend weapons and glue feathers to the ends of arrows and was even found to glue together broken clay pots in Roman Britain. In more recent times, it was used by Soviet soldiers during World War II as a topical medication for burns and wounds, and it was later found to increase the risk of certain cancers.

At several dig sites, archaeologists have discovered small lumps of this material, which often exhibits tooth imprints, suggesting, possibly, the earliest form of chewing gum. According to the U.S. Department of Agriculture, the tar probably had a pleasing taste like resin. This pattern of chewed birch pitch has been seen in archaeology sites in other parts of the world, including Scandinavia and Sweden.

Previous archaeology sites where the birch pitch has been discovered showed evidence that the chewing was probably a step in the tool-making process for the substance to become adhesive.

Samples of this substance, along with teeth marks and partial thumb prints, also contain incredible amounts of human DNA, giving us the most unusually obtained source of Stone Age human genetic information.

“You can recover microbial DNA,” Hannes Schroeder, archaeologist and associate professor at the University of Copenhagen said. “And this opens up whole other possibilities.”

Schroeder studies the application of isotope and ancient DNA analyses and was the lead author of the study. He and his colleagues were able to sequence the human DNA preserved by the birch pitch sample to discover fascinating information about this ancient individual. They determined the person’s sex to be female and, based on the genetic variation in several of the analyzed genes, it is likely that she had dark brown hair, dark skin and blue eyes.

“It’s like having the ghost in front of you,” said Theis Jensen, a graduate student instrumental to Schroeder’s study.

The authors suggest that, based off what is known about the individual, she was likely more closely related to hunter-gatherers from continental Europe than hunter-gatherers from central Scandinavia. The color of the hair, skin and eyes is also indicative of this assumption, as these are characteristic features of European hunter-gatherers from this time.

Gradually, the two groups of hunter-gatherers were forced together due to geographical hardships. However, the authors note that the individual’s genome is entirely composed of Western hunter-gatherer ancestry, indicating she was born before the blend of the two.

The researchers also analyzed the non-human ancient DNA stored in the birch pitch sample and detected bacterial species normally found in the oral microbiome. Some of the discovered species are known pathogens such as Porphyromonas gingivalis, a consequence of gum disease. In fact, the findings show that the oral microbiome of this individual is not too dissimilar from that of humans today.

Additionally, analysis of the DNA sequences showed remnants that could be mapped to plant and animal species such as the hazelnut, mallard and eel. The authors note these traces were likely leftovers from the individual’s most recent meal. This further supports the notion that the ancient individual was a continental European hunter-gatherer, as archaeologists have found great quantities of hazelnut shells in common Neolithic sites. Also based on her genomic analysis, she was actually found to be lactose intolerant.

The use of birch pitch to this extent in ancient human culture baffles scientists to this day. It is unclear how these early humans were able to create the tar in the quantities they did, considering the specific conditions it requires, but it nevertheless played a large role in their everyday lives and leaves behind a rich look into their past.

 

%d bloggers like this: