Cattle, milk, and Europeans
6 January 2014
With their article on 'The milk revolution', Professor Joachim Burger and his work group at the Institute of Anthropology at Johannes Gutenberg University Mainz (JGU) managed to catapult themselves into the media headlines. But milk in fact only represents an incidental aspect of their research. Their real concern is the history of the settlement of Europe.
- Zu Bild 'Professor Dr. Joachim Burger and his work grpoup at the Institute of Anthropology do research on the "milk-revolution". (photo: Stefan F. Sämmer)'
- Zu Bild 'The map shows the origins of lactase persistence in Europe about 7,500 years ago, the pottery stands for the Linear Pottery culture that spread with the lactase persistence. (ill./©: Sabine Schade-Lindig, Joachim Burger, and Yuval Itan)'
- Zu Bild 'The ultra-clean laboratories at the JGU Institute of Anthropology provide best standards for premium quality palaeogenetic research. (photo: Thomas Hartmann)'
- Zu Bild 'Today Burgers work group is an important partner of international projects like the EU-project "Lactase Persistence in the early Cultural History of Europe". (photo: Stefan F. Sämmer)'
Milk, milk, and milk again. "In fact, I’m a little tired of this topic," said Professor Joachim Burger. "I've had to repeat the same things over and over again in interviews."
Yes, Burger and his team at JGU’s Institute of Anthropology published a feature in the specialist journal Nature entitled "The milk revolution." Yes, in this they disclosed the point of time when the first Europeans were able, as adults, to digest fresh milk – a discovery with far-reaching consequences.
"But that actually represented just a sideline of our work," explains the anthropologist, pouring some freshly brewed black tea into two cups. "It's merely one among many of the insights we've gained, but it's the one they keep going on about on TV because it relates directly to everyday life. It's a topic that sells. Toothpaste, razorblades, bread, milk – these are the things that a. For us, however, this milk business is just a minor by-product of our research. What we are actually interested in is the bigger picture – the settlement of Europe after the last Ice Age by both humans and animals."
Farmers migrate to Europe
Burger finds a blank sheet of paper and sketches an outline map of Europe. Italy, Spain, and England take shape on his map…. "Down here we've got Turkey and the Levant. We'll make these a bit larger." He draws two arrows originating from this region that point towards the middle of the sheet. The one curves slightly towards the northeast, the other towards the southwest. "The first farming communities appeared in the Middle East and Anatolia. It was there that sheep, goats, pigs, and cattle were domesticated." And it was there, some 11,000 years ago, that what we call Neolithic culture developed and began to spread outwards to Europe. About 8,400 years ago, it reached Greece and some 400 years later had infiltrated the Balkans.
"We now managed to do something that everybody thought was quite impossible," Burger says with a little pride in his voice. In 2005, in a laboratory specially constructed for the purpose at the Institute of Anthropology at Mainz University, his team was able to sequence not just animal but also human DNA from remains that were thousands of years old.
Specialists had believed that there was far too great a risk that modern nucleic acids would contaminate the ancient human DNA. "They were dogmatic that it just couldn't be done. But it can be done! All you have to do is clean everything as thoroughly as possible." A smile appears on Burger's face. "Well, maybe I'm oversimplifying a bit." But it is the basic principle. Strict hygiene regulations apply to anyone working in the laboratory. "Even our cleaning water has to go under the UV lamps."
One gene decides about the tolerance of milk
Their procedure helped the Mainz-based team tap into a whole new field of research in which they now lead the world and so have come to play a major role in high profile international projects. And at this point, inevitably, we have to turn our attention to milk, the EU project on "Lactase Persistence in the early Cultural History of Europe" or LeCHE for short, and the milk revolution.
When the early farmers moved to Europe they brought their livestock with them. They had already discovered techniques that enabled them to remove the lactose – a milk protein that many adults living today are still unable to digest – from fresh milk: The ancient farmers made cheese and yogurt. This represented an important cultural development. What happened next was that a genetic mutation occurred some 8,000 years ago in Europe. There was a change to one single human gene and this made it possible for a small group to retain the ability to digest milk into adulthood. This was how the 'milk revolution' kicked off.
Burger and his team were able to identify the gene responsible but this then quickly threw up another problem that they set about investigating. "Something like 50 to 90 percent of the current adult population of Central Europe can digest milk. So how did this characteristic manage to spread so rapidly?" When it comes to evolutionary changes, a few thousand years represent no time at all. "What we have here is the interaction between demography and evolution. We can only assume that the evolutionary advantage was so great that this group of people rapidly grew in numbers and the area settled by them massively expanded."
Indiana Jones and the discipline of anthropology
Now statistics and computer science was needed in order to demonstrate that this was what actually happened. "People seem to have this idea that anthropologists lead an exciting, Indiana Jones-like existence. I try to disabuse my students of this misconception as soon as possible. Anthropology in our case means hours of work in the laboratory and in particular in front of the computer screen." Complex programs are used to play through various scenarios. "We are always on the lookout for people with the necessary skills."
But Burger is keen to lead the conversation away from milk again. "When the farmers migrated to Europe they encountered a population of hunter-gatherers. We wanted to know from which of the two groups we present-day Europeans descend. What we found was that it was neither – or rather both." It was only when these groups intermingled that the ancestor of the modern European was born.
But it took 2,000 years before this fusion occurred, another fact discovered by Burger and his team. "The farmers were happy the way they were, as were the hunters and gatherers. There was no immediate reason for either group to adopt the lifestyle of the other."
The long road to the modern European
Although the farmers’ settled life had its advantages, there was also a price to pay. Their carbohydrate-rich diet was a source of rapid energy but also produced unfortunate side-effects, such as caries. The so-called diseases of civilization appeared and there was even the risk of epidemics. The hunter-gatherers led healthier but also more hazardous and shorter lives.
The farmers bred more rapidly than the other group; their birth rate was four times greater than that of the hunters and gatherers. This was attributable to both to the high carbohydrate diet and the fact that they had secure accommodation. "They were able to provide their children with suitable shelter." This had a definite knock-on effect. Women from the hunter-gatherer communities did intermarry with the farmers and they probably saw this as an enhancement of their social status. There was very little traffic the other way.
Because this amalgamation was so gradual, it took more than 2,000 years before the hunter-gatherers were subsumed in the farming community. With this finding, Burger's team has been able to add another piece to the puzzle that is the post-Ice Age settlement of Europe.
Much has been revealed since 2005 and there are so many new avenues to explore that Burger already has new research projects in mind. "The Migration Period would be a fascinating subject," he speculates, "Then there's Central Asia." He pauses for a moment and then lifts the teapot from the warmer. "More tea?" he asks. Yes please. But no milk, thank you.