Today, I learned that eels are fish

Summary

Let’s dive right in: for most of history, we didn’t really know where eels come from. Which is strange, because they’re everywhere—rivers, lakes, oceans. Even now, we only have the faintest sense of where they spawn or how. Their lives remain partly hidden, and that blank space has always invited stories.Aristotle thought they slithered out of mud, giving the primordial ooze its first big break. Another tale claimed they rose from sea foam, like a grotesque remix of Aphrodite’s birth. Japanese folklore said eels began as earthworms blessed by the summer moon—plausible enough, if you consider being transformed into something both hideous and delicious a blessing. For millennia, our relationship with eels was governed by fables and speculation. Eventually, real science needed to step in.One spat of scientific interest in eels came at the end of the 19th century. Scientists, lit up by the potential of Darwin’s new theory of evolution, believed they finally had the tools to crack the mysterious origins of eels: how they mated, where they were born, and where they eventually went to die. The scientists observed. They dissected. They experimented. And time after time, they kept hitting dead ends.Here’s the story of one such dead end. The year is 1876, in the port of Trieste, Italy—then part of the Austro-Hungarian Empire. In a small lab, surrounded by jars of eels, briny seawater, and plenty of slime, a young zoology student works under orders from his doctoral advisor. His task: to solve the mystery of eels by capturing live specimens from the harbor and slitting open their bellies in search of testes. (The sexual mysteries of eels were anatomical as much as behavioral.) Day after day, he probed and sliced, logging hours at the dissection table. Four months later, he left empty-handed, without so much as a glimpse of a gonad. Upon his departure he wrote: “All I see when I close my eyes is the shimmering dead tissue, which haunts my dreams...” Yikes.That student was Sigmu...