Scientists have reconstructed the genome of an ancient human who lived around 5,700 years ago in what we know as southern Denmark.
There are no known physical remains of the woman in the study. All that the researchers have to go on with is just a small lump of birch pitch, which is an ancient tar-like substance distilled from heated tree bark. This sticky blob was enough to tell the researchers that the woman once walked the Earth, and it also hinted at numerous clues about her identity.
A chewing gum helped the research
The reason for that is because birch pitch was sometimes chewed by ancient humans, and they were also used as an adhesive on weapons and stone tools as far back as the Middle Pleistocene, which ended 126,000 years ago. The chewing gum is thought to have been for numerous purposes, including to warm the pitch up, making it soft and malleable for glue use, and also as a medicine, or even for recreational purposes, like modern-day chewing gum.
Regardless of the reason, when the scientists discovered the well-preserved specimens of this substance that was chewed by humans years ago, traces of saliva can sometimes still be found contained within the gum, enabling the scientists to reconstruct genetic information.
In the case of the sample from Denmark, it enabled the ancient chewer's entire genome to be reconstructed, a feat that the researchers say has never been done before in the absence of skeletal remains.
Hannes Schroeder, the lead researcher and evolutionary genomicist from the University of Copenhagen, said that it is amazing to have gotten a complete ancient human genome from anything other than bone. By sequencing the sample, they discovered not only the ancient human DNA but also microbial DNA reflecting the oral microbiome of the person who chewed the pitch, along with plant and animal DNA that could correspond to a recent meal eaten by the person.
The research team explained that the DNA is so exceptionally well preserved that they were able to recover a complete ancient human genome from the sample, which is significant since no human remains have been recovered from the site. The results highlight the potential of chewed birch pitch as a source of ancient human and non-human DNA, which can be used to shed light on the population history, subsistence strategies, and health status of ancient populations.
Revelations about the ancestor
In terms of the ancient chewing gum, so much light has been shed. The DNA in the sample suggests the chewer was female, most likely with dark skin, blue eyes, and dark brown hair. Researchers say that it is comparable in quality to well-preserved teeth and skull bones.
The authors of the study explained that this combination of physical traits had been noted previously in other European hunter-gatherers, suggesting that this phenotype was widespread in Mesolithic Europe and that the adaptive spread of light skin pigmentation in European populations only happened later in prehistory.
The results of the study also suggest that her ancestry stemmed from mainland Europe instead of the hunter-gatherer populations who lived in central Scandinavia and that she existed during a time of transition when a period known as the Late Mesolithic Ertebolle culture gave way to early Neolithic Funnel Beaker culture.
That change brought the early farming societies, but the Syltholm individuals' DNA does not carry any Neolithic farmer ancestry. This means that not only did she fell on the hunter-gatherer side of the equation, but she was also involved in the development of agriculture in the region, and the development may have been slower than what the researchers thought.
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