In a dusty Mexican rainforest and on a Spanish island, researchers hunted for creatures so small and elusive that it took ten people a week to find a single one. Those tiny millipedes—barely a centimeter long, living their entire lives underground—held the key to solving a mystery that had puzzled scientists for over a century. Now, a Virginia Tech-led team has finally completed the first evolutionary history of all living millipede orders, and the story they've uncovered rewrites what we thought we knew about life's colonization of Earth.
For decades, scientists had identified two rare groups of millipedes called Siphoniulida and Siphonocryptida, yet without fresh DNA samples, they couldn't determine where these creatures fit in the millipede family tree. "These last two were kind of like our white whales," said Paul Marek, the study's lead investigator and associate professor at Virginia Tech's Department of Entomology. The breakthrough came when researchers collected Siphoniulus neotropicus from Los Tuxtlas, Mexico, and Hirudicryptus canariensis from the Canary Islands—the first DNA samples of these species ever sequenced for evolutionary analysis. As first author Luisa "Fernanda" Vasquez-Valverde recalled, the search was painstaking: "Finding them in the field was hard because we were just seeing this little white nematode. We didn't know for sure it was a millipede until we looked under the microscope."
By sequencing DNA from these two elusive species and comparing hundreds of genes across 82 millipede species total, combined with evidence from 29 fossils, the team reconstructed millipede evolutionary history stretching back nearly 460 million years—roughly 35 million years earlier than the oldest known millipede fossils and far more ancient than previously believed. The findings, published in Current Biology, revealed that one group, Siphonocryptida, wasn't a distinct order after all but part of an existing lineage, while Siphoniulida was finally placed among its closest relatives on the timeline.
What makes this discovery so striking is what millipedes were doing during those earliest epochs. "Millipedes beat vertebrates onto land by more than 80 million years," Marek explained. "They really set the stage for later life on land, including humans and vertebrates." Back then, Earth was an alien world—no trees, no leaves, no flowering plants, no seeds, no vertebrates. Millipedes were the pioneers, breaking down decaying mosses and organic material, recycling nutrients and helping establish the very first terrestrial ecosystems. They were feeding on, as Marek vividly put it, "decaying mosses, decomposed slime and primordial gunk on the surface of the Earth."
The completed evolutionary tree also illuminated one of millipedes' most remarkable adaptations: chemical defense. The analysis traces the origin of these "chemical weapons"—the toxic compounds millipedes produce to protect themselves—to approximately 260 million years ago. "They're little chemical factories," Marek said. The research required terabytes of genetic data and relied on Virginia Tech's Advanced Research Computing resources to process and analyze relationships spanning hundreds of millions of years.
Perhaps the biggest surprise, according to Marek, was simply how ancient these millipede lineages turned out to be. In solving this century-old puzzle, scientists have revealed that the humble millipede is far more than a decomposer crawling through the soil—it's a living link to the earliest chapters of terrestrial life itself.