Stone Age Lola had dark skin and blue eyes

 

Sometimes small, apparently insignificant archaeological finds tell the biggest stories. This is the remarkable account of how a 5700-year-old lump of birch-pitch chewing gum was found to contain DNA from the girl or woman who had chewed it.

DNA scientists have, for the very first time, extracted a complete human genome and mapped the genetic material of a person, who lived during the time when agriculture came to what we today call Denmark, and whose ancestors were the hunter-gatherers who had lived there for millennia.

Lola, the name we have chosen to give this girl or woman, did not look at all like modern Danes. Her DNA reveals that she probably had dark skin, blue eyes and dark-brown hair. The chewing gum also contained DNA from the food she had recently eaten.

This account is based on conversations with associate professor Dr Hannes Schroeder and Theis Trolle Jensen from the Section for Evogenomics, Globe Institute, University of Copenhagen, and Dr Søren Anker Sørensen from Museum Lolland-Falster, who have recently published their research results in the international scientific journal Nature Communications.

 

 

The projekt

This account is based on conversations with the scientists that have recently published their findings in the international scientific journal Nature Communications. The project is led by associate professor Dr Hannes Schroeder and Theis Trolle Jensen from the Section for Evogenomics, Globe Institute, University of Copenhagen, who have jointly been responsible for analysing the lump of birch pitch. The work was undertaken in connection with Theis Trolle Jensen’s double PhD project (University of Copenhagen and University of York), and was financed by the EU (ArchSci 2020) together with a foundation grant to Hannes Schroeder. It was carried out in collaboration with research coordinator Dr Søren Anker Sørensen of Museum Lolland-Falster and several other researchers. Søren Anker Sørensen is an archaeologist and one of Denmark’s leading experts on the Mesolithic and the introduction of agriculture to Denmark.

 

Drawing: Tom Björklund

Chewing gum conjured up an image of Lola

 

Begklump

Sometime back in the Stone Age, Lola sat on a beach and chewed a lump of birch pitch. This was about 5700 years ago; a radiocarbon date for the pitch reveals that it took place between 3850 and 3650 BCE. Even though the date has an error margin of almost 200 years, it is absolutely critical to the story, but more on this later.

Behind Lola stretched a flat wooded landscape – what we know today as the eastern Baltic island of Lolland. In front of her, as far as the eye could see, extended a shallow lagoon, now known as Syltholm Fjord, an area of reclaimed land to the east of Rødbyhavn.

Lola had just eaten meat or eggs from two mallards, together with a handful of hazelnuts. She had finished here meal and began to chew on a lump of birch pitch. After a while, she spat it out into the water.

Then, one day in 2015, the little lump of pitch turned up in an archaeological excavation. It was found by archaeologists from Museum Lolland-Falster. They were digging in the reclaimed fjord in advance of the construction of a tunnel linking Denmark and Germany, which will cut through the fjord.

Around 5700 years had elapsed since the lump of pitch was ejected from the woman’s mouth, and she is long dead and gone. Nevertheless, it has, in a way, brought her back to life.

It was Theis Trolle Jensen who believed that the little lump of pitch could possibly contain traces of ancient DNA. He took part in the excavation and knew of similar discoveries in Sweden. These lumps consist of pitch extracted from birch bark and are not uncommon finds. The greyish-black birch pitch becomes soft when heated and stiffens as it cools. In the Stone Age, it was used as an adhesive, for example for attaching arrowheads to arrow shafts. But it was also used as chewing gum. There are no tooth marks in the lump, but it is folded and twisted in the same way as a well-chewed piece of modern chewing gum. It probably cleaned the chewer’s teeth and acted as a mild antiseptic.

A 5700-year-old mouth swab

Perhaps Lola chewed on the pitch to make it soft and flexible, while cleaning her teeth and mouth at the same time. The pitch is a bactericide and this property helped preserve the DNA in her saliva, which became sealed within the lump. We do not know what it tasted like, but some people maintain that it is rather like chewing tobacco.

Theis Trolle Jensen’s hunch proved to be well-founded – the pitch did actually contain genetic material. This was a sensational discovery – now scientists do not need the bones of prehistoric people to be able to extract their DNA, a small lump of pitch is quite enough!

He explains that the chewing gum had functioned just like the cotton buds used for mouth swabs by geneticists and forensic scientists today. These absorb saliva from the mouth, which contains everything a geneticist needs to map a person’s genome.

The scientists were not only able to extract the woman’s DNA from the remains of saliva sealed in the lump of pitch, but also genetic material from the ingredients of her most recent meal, eaten just before she put the chewing gum in her mouth.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ancient hunter-gatherers

Hannes Schroeder says the DNA they have extracted is from a woman or a girl, but it cannot reveal anything about her age. He explains that, due to specific mutations in her genome, much can be said about the colour of Lola’s skin, hair and eyes, even though it is difficult to be absolutely sure.

Lola’s skin was almost certainly brown, perhaps even very dark brown. Her hair too was brown to very dark brown, and her eyes were blue. She was lactose intolerant, which means that she could not break down and digest lactose. Even the DNA of viruses and bacteria in her saliva are preserved: Lola was a carrier of a herpes virus that can cause mononucleosis, better known as the kissing disease, and a specific streptococcus that can cause pneumonia.

There were two population groups of hunter-gatherers in Europe from the end of the ice age until the introduction of agriculture. Lola belonged to the western group, which was widespread in Western Europe and is known from human remains found in Spain and the British Isles. These individuals appear to carry the same phenotypical features, for example dark skin, dark hair and blue eyes. It is interesting that the geneticists have not detected any traces of DNA from either the eastern group of hunter-gatherers or Central European farmers in Lola’s DNA. Her genome belongs exclusively to the western group of hunter-gatherers, with no intermixture, explains Hannes Schroeder. It is interesting that she lived during a period when agriculture had already arrived in Denmark, but in genetic terms she resembled a hunter-gatherer, interjects Theis Trolle Jensen.

Lola’s facial features resembled ours

Lola’s ancestors had kept their dark skin colour with them when they left Africa many millennia previously. After the end of the ice age, about 15,000 years ago, some of them settled in what is now Denmark. The eastern hunter-gatherers settled in Northern Norway and Sweden, and Denmark appears to have been a borderland between these two population groups.

Lola has only her skin colour in common with the past and present inhabitants of sub-Saharan Africa. Even though archaeologists have not found any of her bones, not even her skull, many other Mesolithic skulls have been found in Denmark over the years. Physical anthropologists, scientists who study prehistoric skeletons, all agree that Mesolithic people in Denmark had European features, albeit with very robust muscular attachments and a broader jaw than we have today. So, they were very similar to us, apart from their skin pigment, hair colour and a broader jaw.

Very little remains of Lola’s genetic material in the genomes of people living in Denmark today. Mutations and successive immigrations during the past 6000 years have had a huge effect on our DNA: New genes have been added, while others have been lost. Nevertheless, most people in Denmark probably still carry traces of genes from Lola and the western hunter-gatherers.

Mallards and nuts

Perhaps Lola was one of the last people in Denmark to subsist exclusively by hunting, fishing and gathering. She lived in a time when agriculture had arrived in Denmark. Søren Anker Sørensen is research coordinator for the archaeological investigations associated with the construction of the Fehmarn Belt Fixed Link. He tells that agriculture came to Denmark in around 3950 BCE, i.e. 100 to 300 years before Lola’s time.

 

 

 

 

 

 

 

 

But did Lola and the other people on her settlement live as hunter-gatherers like their ancestors, or were they farmers? The little lump of pitch also contained DNA from a meal Lola had eaten just before she began chewing on it: A meal containing the meat or eggs of two mallards, together with some hazelnuts – food from the natural environment in and around the fjord where she lived.

On the face of it, it seems likely that Lola lived as a hunter-gatherer, subsisting on the wild food that nature provided. But, according to Søren Anker Sørensen, it is not quite as simple as that.

The lump of pitch provides us with a snapshot: It only tells us about one of the many meals Lola ate during her lifetime. It is not possible to say anything in general about her diet, based on this single meal. It would be like concluding that a confirmed carnivore, who had eaten a vegan meal before being sampled for DNA via a mouth swab, was a vegan because their saliva did not contain animal DNA. On the day before Lola may well have eaten meat from domesticated animals and bread baked with grain, the DNA of which can no longer be traced.

Bones can reveal whether Lola was a hunter-gatherer

Lola is like a shadow. We only know her through her DNA – archaeologists have not found even one of her bones. Important trace elements in her skeleton would have been able to reveal more about her diet. The 13C content reveals whether food came primarily from the sea or the land, or was a mixture of the two. Analyses of human bones show that the hunter-gatherers, who were Lola ancestors, obtained a great proportion of their food from the sea in the form of fish and shellfish. Conversely, analyses of the first farmers in Denmark show that their food was derived from grain and the meat of domesticated animals. The content of the nitrogen isotope 15N in bones can also reveal the position of humans in the food chain. Analyses show that the food of hunter-gatherers contained a large proportion of animal food, while agriculturalists had a more plant-based diet.

Just one bone from Lola could reveal whether she was one of the last people who subsisted by hunting, fishing and gathering, as people had done for millennia, or whether she was one of the first who lived by farming: A new lifestyle that people had either acquired through contacts with farmers south of the Baltic, or learned from farmers who had immigrated and settled in what is now Denmark.

Did the local hunter-gatherers become farmers?

Agriculture came to Denmark between 100 and 300 years before Lola lived. It happened around 3950 BCE. Many traces of the first farmers and their animals have been found during the excavations in advance of the Fehmarn Belt Fixed Link, but who were the first farmers? Søren Anker Sørensen is trying to find the answer to this question.

One theory is that the original population, to which Lola belonged, had contact with farmers in Continental Europe over several centuries. Slowly, but surely, they acquired knowledge of crops, cultivation methods, domesticated animals and animal husbandry. They became gradually accustomed to agriculture and adopted the aspects they found useful and, little by little, these developments led to them becoming full-time farmers.

Hunter-gatherers on Lolland also had contact with the farmers in the south. Archaeologists have found a so-called shoe-last stone axe during excavations in Syltholm Fjord. It was made by farmers who lived in what is now the Czech Republic. We do not know whether the two groups actually met one another face to face; axes can be readily passed from hand to hand.

If they learned how to cultivate the soil and keep animals from the farmers to the south, then they made a conscious choice to be farmers. There is no evidence to suggest that hunter-gatherers in Denmark were forced to change their lifestyle because of failing fishery, hunting or gathering. There were no climate-related or environmental catastrophes, and there is nothing to suggest that they over-exploited their game animals.

Did immigrants bring agriculture?

The most recent theories suggest that there was direct immigration of farmers from Western Europe. The question is then: What was the scale of this immigration, and what happened to the original population? It is here that Lola can shed some light on the transitional period when Danes became farmers.

Immigrant farmers settled to cultivate the soil while there were still hunter-gatherers living in Denmark. Some people believe that the agriculturalists dispatched scouts to find out where it was possible to settle, the rest then followed and established themselves there. The two populations – farmers and hunter-gatherers – exploited different zones in the landscape. The hunter-gatherers lived along the coast, where the fishing was good, and they could hunt in the forests in the hinterland. The farmers settled on the light soils in the interior. They each lived their own lives and did not compete for territory.

Domesticated animals and crops were introduced. Sheep and goats do not live naturally in Northern Europe. They were the descendants of the sheep and goats domesticated in the Middle East. The excavations in advance of the Fehmarn Belt Fixed Link have yielded the oldest bones of goat yet found in Denmark, dated to 4044-3960 BCE – from a goat that lived long before Lola. The grain that the Stone Age farmers cultivated also came originally from the Middle East, and the same is true of domesticated cattle. Even though aurochs (wild cattle) lived in Western Denmark, it was not these that the first farmers domesticated.

Søren Anker Sørensen believes it is possible that foreigners brought agriculture to Denmark. To the south, on the other side of the lagoon where Lola lived her life, lies the Continent. It was from here that the first farmers came to Denmark, crossing the narrow strait between the islands of Fehmarn and Lolland. The shortest distance across the water here is only 18 km. Land is visible on the other side, giving something to aim for when they set off with their valuable cargo of seed corn, goats and cattle. Who knows – Lola may have seen some of them coming ashore?

Two lifestyles fuse together

If there was immigration, perhaps several generations elapsed before everyone had adopted agriculture. Becoming a farmer is not something that happens from one day to the next. It is no coincidence that modern farmers take a degree course in agriculture. Being a farmer requires extensive knowledge of soils, crops and livestock. How do you keep the animals alive, and how do you select individuals for breeding? While hunters shoot and kill the animals they eat, a farmer must always secure animals for breeding. Farmers therefore never eat their last animals.

For a time, farmers and hunters perhaps lived side by side, each with their own lifestyle. Maybe they traded with each other: Hunter-gatherers bartering game and fish for agricultural produce, but probably not milk, to which they were allergic. During the excavations in Syltholm Fjord, archaeologists have found the remains of fish weirs, which all date from the time after the introduction of agriculture. This suggests that some people continued their traditional way of life, while others perhaps chose to adopt agriculture. In the course of several generations, the two lifestyles fused together to form a new common lifestyle. Was Lola one of the last hunter-gatherers in Denmark or had she and her kin already adopted agriculture? Did she live with one of the farmers who had come to the country? Future research and further DNA analyses will surely take us closer to answering the question of why we became farmers in Denmark 6000 years ago.

Credits:

Many thanks are due to Femern A/S, European Union’s Horizon 2020 research and innovation programme under grant agreement no. 676154 (ArchSci2020) and Villum Fonden (grant no. 22917).