The Museum für Naturkunde, a natural history museum in Berlin, is the perfect place for Struck, 56, a micropaleontologist, to work. Struck is also the head of the museum’s isotope lab. He specializes in a method of analysis that provides answers to a whole host of exciting questions asked by paleontologists, anthropologists, hydrogeologists, climate scientists, and medical researchers alike, such as: What were the lives of people and animals like thousands or millions of years ago? Who was the hunter, and who the prey? And what was the climate like back then?

A tiny bone sample tells whether a prehistoric animal was a carnivore or a plant eater. In the same way, a sliver of fingernail is enough to show whether a person nowadays is actually a vegan or just a “flexitarian.” You are what you eat – it’s a timeless piece of wisdom, and it was as true then as it is today. The differences are minor, in the per mille range, but they can be shown with pinpoint accuracy, even 300 million years later.

This is possible because certain varieties of the elements that make up an animal’s diet build up in the body over time. “We can clearly see this from the isotopic signature of carbon and nitrogen. The lower the nitrogen signature we find in a sample, the more plant-based the diet was,” Struck explains. He analyzes the tiniest building blocks that remain of life, even if that life ended millions of years before: the stable isotopes of the chemical elements carbon, nitrogen, and oxygen.

Traces of Life Forms from Prehistory Can Still Be Read Today

Most elements consist of atoms whose mass varies slightly, known as isotopes: Nitrogen, for example, consists of 14N and 15N, and carbon of 12C and 13C, with traces of unstable 14C. The “isotopic signature” of a plant or animal product can also vary widely by region, which means these signatures can even be used to show the origin of foods.

Time-series measurements of sediment samples and fossils from the world’s oceans make it possible to trace changes in climate over millennia. The ratio of oxygen isotopes (18O/16O) is what makes this possible; the lower the proportion of 18O, the warmer the climate was. From solids to liquids and gases, mass spectrometers can ionize almost anything and break it down into specific masses in an electrical field. Bones, teeth, muscle tissue, limestone deposits (Muschelkalk), and minerals can be analyzed this way, as can oils, water samples, and even the air we breathe.

By appointing Struck a professor at the Institute of Geological Sciences, Freie Universität Berlin aims to strengthen research and teaching activities in paleontology while also intensifying ties with the Museum für Naturkunde. This is the first professorship of isotope paleontology in Germany.

It did not go without saying that Struck would pursue an academic career. He grew up in a small town to the south of Rendsburg, near the northern German city of Kiel. He was one of eight children, which must have helped to make him such a down-to-earth, approachable person. Stability, skill with working with his hands, and pleasure in “creating something of good quality in practical terms” were all things he learned from his father, who was a mason.

They also spent years playing music together in the fire department marching band. The father played the horn, and the son played clarinet. His mother, who worked part-time as a secretary, made sure the children didn’t just devour comics, but read nonfiction as well. It had a lasting impact. The German version of Adrian Desmond’s book The Hot-Blooded Dinosaurs: A Revolution in Paleontology fascinated Struck so much that he decided to study geology and paleontology at the university in Kiel. “Unfortunately, dinosaur paleontology wasn’t offered there,” he says.

He was lucky to be the seventh child, since only the four younger children got the chance to go to academic secondary school. After that, he commuted daily to attend lectures in Kiel, since there was no money for a room in the city. “I did miss out on student night life, of course,” he says with a smile.

Field mapping was an essential part of the degree of Diplom in geology. Struck flew to the Arctic island of Spitsbergen to do his part in 1987. “A helicopter put down four expedition crates, my fellow students, and me in the middle of nowhere, and then we set off.” He will never forget the seven-week adventure. “We camped in a tent at the start. After that, some Russian researchers who were going home left us their cabin.”

For his dissertation, Struck traced tiny ocean fossils known as foraminafera, and how changes in climate affected the development of foraminafera populations in the Norwegian Sea. He had finally become a paleontologist – or, to be precise, a micropaleontologist. Isotope analysis became the centerpiece of his research, and many further trips on research vessels followed.

Struck then moved to the Leibniz Institute for Baltic Sea Research, in Warnemünde, which had been founded in 1992, as a postdoc. He worked at the new isotope lab there, where he studied the nitrogen cycle in the Baltic Sea. “15N/14N analyses of things like cyanobacteria can be used to show where their nutrients come from,” he explains. The overfertilization of the Baltic Sea with nitrogen input from agriculture is also documented in this way.

Like many scientists who wish to embark on an academic career, Struck had to make his way from one fixed-term contract to another. Then, in the year 2000, he finally moved to Ludwig-Maximilians-Universität in Munich, where he substituted for a professor. Two years later, he was tapped to head the isotope lab at the Bavarian State Collection for Paleontology and Geology, which is housed at the university. It was his first permanent position.

In 2006, when Reinhold Leinfelder, then the head of the institute where Struck was working – and now a professor at Freie Universität Berlin – moved to the German capital to serve as director of the Museum für Naturkunde, he asked Struck to come along. Struck was only too happy to comply. He and his wife, hydrogeologist Marianne Falk, worked together to build the isotope lab there. He completed his habilitation in 2008 and then began teaching as a lecturer at Freie Universität.

Mystery of the Dinosaurs Solved: They Were in Fact Warm-blooded

The mystery of the dinosaurs that had sparked Struck’s interest as a child was finally solved in 2010. As the author Adrian Desmond had suspected based on various physical features of these huge animals, they were in fact warm-blooded, unlike other saurians. “Isotope thermometry” was partly responsible for proving this, which Struck is especially pleased about.

“It’s fantastic that the method I represent helped to clarify the question that got me started in paleontology in the first place!” He was not involved in the project himself, but samples from a Brachiosaurus – whose correct name is actually Giraffatitan brancai – from the Museum für Naturkunde in Berlin were among those analyzed for the research. “I got my doctorate in 1992. Now, 25 years later, I’ve become a professor,” he says in the end with a smile. “It was a pretty long time to spend training for the job,” he says. Then again, in geological time, it’s barely a blink of an eye.