Who was the first to draw and label the brain of an insect? It’s not a question that many have pondered, but Andrea Strazzoni believes that he may have the answer.

Strazzoni is more than a philosopher, historian, or scientist – his work sits at the intersection of all three. Although Italian, his love for the history of philosophy and science led him towards the Netherlands, specifically the Dutch intellectuals of the 17th and 18th centuries. “Most of my research is concerned with professors, scientists, and other figures related to Leiden,” he says.

One such Leiden intellectual is Jan Swammerdam (1637-1680). Like Strazzoni, Swammerdam sat at the intersection of various fields. He was a pupil of Leiden’s great Franciscus Sylvius, who made many discoveries in human anatomy and was one of the first to realize that the human body runs on chemical processes.

With Sylvius’ training, Swammerdam explored human respiration, dissected dogs, and studied everything from frogs to snails to lice. Strazzoni’s most recent article in Royal Society Journal Of The History And Science, however, focuses on something even smaller: Swammerdam’s diagram of a honeybee’s brain.

one millimeter

The illustration may not look like much compared to modern computer-generated reconstructions, but Swammerdam was doing something that had never been done before. With just a simple microscope, Swammerdam mapped out the various nerves and organs of a bee’s brain. For reference, a honeybee’s brain is about a millimeter long, smaller than a grain of rice.

Swammerdam’s microscope was nothing like the ones we have today. Modern biological microscopes are often compound, meaning they use multiple lenses to get a higher magnification. Swammerdam’s microscope had a single lens, homemade, and it had to be pressed directly against the sample. His tools were rudimentary, but he made up for it with a talent for illustration.

“Swammerdam was an exceptionally gifted drawer,” says Strazzoni. He made this description in the 1670s, but it wasn’t until mid-19th century – and the birth of microphotography – that we have anything with a similar level of detail.

These very accurate illustrations came from an obsession with meticulous observation. “Swammerdam was always very cautious in not writing down what he could not observe,” Strazzoni explains. Even regarding the discoveries of his contemporaries, “he says, well, I could not observe this, so I better not talk about it.”

Still, Swammerdam’s bee brain went through a few drafts. Before the final published version, there is an older drawing, perhaps a letter to be sent to another scholar. It’s this earlier, unpublished version that Strazzoni finds particularly interesting.

Bold claims

In this first draft, Swammerdam is more bold with his claims. Heavily influenced by the ideas of the prominent philosopher René Descartes, Swammerdam looked at a honeybee’s brain and saw some features that weren’t actually there. “So for instance, we have the reference to the pineal gland, and the pineal gland was a trademark of Cartesian neurophysiology,” Strazzoni explains.

Cartesian science and philosophy was popular in the Netherlands at the time. Although Descartes thought that bodies functioned essentially like machines, he also believed in a separate, but interacting soul. He proposed that the soul was tied with the body at the pineal gland, a tiny structure in the centre of the brain. We now know that this gland actually produces melatonin, which regulates your sleep cycle.

In his illustration, Swammerdam also labelled a cerebellum, another brain structure that insects do not have. He later corrected himself about the pineal gland, but the cerebellum remained in his final publication: Bybel der natuure.

Also known as Biblia naturae – Swammerdam’s magnum opus is in both Dutch and Latin. Which version does Strazzoni read for his research? “Basically both,” he says. “The translated ones are quite interesting because they were translated by Boerhaave, one of the foremost figures of the Leiden intellectual environment at the time.”

Herman Boerhaave was a professor and rector at the University of Leiden, as well as director of the Hortus botanicus. He made many advancements in botany, and his school of medicine was renowned around Europe. The anatomical theatre where he worked (as well as some of Swammerdam’s sketches) can still be seen today at the Rijksmuseum Boerhaave. Although Swammerdam preferred to write in Dutch, his work was translated into the scientific language of the time by Herman Boerhaave’s “editorial team.”

Leiden in the early modern period can be described as “a very eclectic institution.” Although the university was founded in 1575 as a protestant rival to the (very Catholic) University of Leuven, Strazzoni explains that by this period “it was not just a university for theologians”. “You have a botanical garden, the university library, the chemical laboratory, an astronomical observatory.” Strazzoni also mentions a theatre for physics experiments, founded by a friend of Swammerdam.

Still, a shared attitude tied these institutions together. Like Swammerdam, the university was focused on experimental evidence and the philosophy of Descartes. “But it was not just that – it was also the general attitude of openness, a lot of professors with a lot of different orientations and a lot of mixing between different paradigms.”

Never out of fashion

The early modern period was also the so-called renaissance of the honeybee. “Honeybees never came out of fashion,” notes Strazzoni, but they certainly became more popular. There was a financial interest in honey production, of course, but honeybees were also an important symbol. “They were social insects… they had a monarchy. For a long time, it was believed that there was a king of the honeybees.”

Swammerdam didn’t care much about this symbolism – in fact, he helped prove that honeybees actually had a queen – but he still had caught the bee fever, and his early description of bee brains was quite far ahead of its time.

“What’s interesting is that he observed what are now known as mushroom bodies. He observed them for the first time and he quite visually emphasized their presence in the brain.” It turns out that what Swammerdam thought was the cerebellum was actually these mushroom bodies (named after their fungus-like shape). This organ is uniquely important for the social behaviour of insects – although this wasn’t realized until a few hundred years later.

Swammerdam’s Bybel had another timely foresight about bees. It was the 1670s, when France invaded the Netherlands. He writes that “very few females are to be found in these unhappy times, whose wars and slaughters have destroyed even the Bees in our country.”

Strazzoni relates this to how we view honeybees today: important for planetary health and even our own survival. “Well, for different reasons of course,” Strazzoni admits. “He was not talking about an environmental crisis or a climate crisis, but there was this statement of how humans can influence the presence of honeybees.”