Scientists Just Reconstructed the Family Tree of Earth’s First Land Animals

Millipedes existed long before the earliest vertebrates ever set foot on dry land. Arthropod decomposers like these recycled nutrients hundreds of millions of years before the first dinosaurs, helping create the earliest terrestrial ecosystems on Earth. Yet their evolutionary story has remained largely unwritten, until recently.

Now, a research team led by Virginia Tech has filled in one of the most significant gaps in our understanding of how millipedes evolved. Their study, which appears in Current Biology, combines genomic data from living species and fossil evidence to produce, for the first time, a detailed evolutionary timeline of all extant millipede orders. The results suggest that the group was already around 460 million years ago, long before the oldest millipede fossil.

“Millipedes beat vertebrates onto land by more than 80 million years,” said Paul Marek, the study’s lead investigator. “They really set the stage for later life on land, including humans and vertebrates.”

Biologists had long known that two groups were extant and very rare, Siphoniulida and Siphonocryptida, but this currently required fresh DNA material to populate the entire phylogenetic tree.

“These last two were kind of like our white whales,” Marek admitted.

Field clicks led researchers to Mexico and Spain, specifically the Los Tuxtlas region and the Canary Islands, respectively. They searched for elusive species at these locations, like Siphoniulus neotropicus and Hirudicryptus canariensis.

“It took 10 people over a week just to find this one tiny 10‑millimeter adult,” recalled Luisa ‘Fernanda’ Vasquez‑Valverde, first author of the paper. “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.”

The team sequenced DNA from these rare specimens, compared hundreds of genes across 82 species, and combined this with data from 29 fossils to build phylogenetic relationships spanning nearly half a billion years. It turned out the groups were not evolutionarily distinct after all, and one group was finally placed where it belonged on the timeline.

The resulting data suggest millipedes evolved only in the last 460 million years, around 35 million years before the earliest fossil record confirming their existence.

“The biggest surprise was just how ancient some of these lineages turned out to be,” Marek said.

At that time, Earth was unrecognizable. “There were no vertebrates, no trees, no leaves, no flowering plants, no plants with seeds,” Marek explained. “Millipedes were feeding on decaying mosses, decomposed slime, and primordial gunk on the surface of the Earth.”

The reconstructed family tree also provided hints about how and when millipedes evolved one of their most defining characteristics: toxic defenses.

“They made the first chemical weapons,” Marek said. “They’re little chemical factories.”

To determine when these defenses first emerged, scientists traced them back to about 260 million years ago, giving the clearest snapshot yet of when millipedes evolved their chemical repellents.

Millipedes still serve as important decomposers, feeding on decaying plant matter and returning nutrients to the soil. However, their contributions to ecosystems are frequently forgotten.

“It’s really kind of puzzling that they have such an important function in the ecosystem, and yet they’re so poorly known,” Marek said.

Taxonomists have described more than 14,000 species, but tens of thousands are expected to remain formally unidentified. Marek’s team has also discovered new species in heavily trafficked areas, including the Virginia Tech campus and the Los Angeles basin.

That enduring question, according to Vasquez‑Valverde, is one of the attractions of the study:

And you can imagine that there could be all this potential for discovery. It leaves me to wonder what else we are set to discover.