Millipedes Colonized Land 80 Million Years Earlier Than Previously Thought

New genetic analysis reveals that millipedes moved from water to land approximately 460 million years ago, a timeline that predates the emergence of vertebrate ancestors on land by roughly 80 million years. According to a study published in the journal Current Biology, this evolutionary shift occurred during the Ordovician period, establishing millipedes as some of the earliest pioneers of terrestrial life.

How Researchers Reconstructed the Millipede Timeline

A research team led by scientists at Virginia Tech utilized modern genomic sequencing to refine the evolutionary history of millipedes, or Diplopoda. The researchers collected samples from two groups of millipedes whose evolutionary placement had remained uncertain. By comparing hundreds of genes from these specimens against 82 known species and integrating morphological data from the fossil record, the team built a comprehensive evolutionary tree.

This method allowed the team to place these groups within the broader millipede phylogeny and estimate their divergence dates. The results indicate that millipedes originated about 35 million years earlier than the oldest known millipede fossils currently discovered. This suggests that the fossil record for these arthropods is significantly incomplete, likely due to the difficulty of preserving soft-bodied organisms from the early Paleozoic era.

Why Millipedes Were Essential to Early Ecosystems

During the Ordovician period, the Earth’s landmasses lacked the complex forests and vascular plants common today. Millipedes functioned as early decomposers in a landscape dominated by mosses and liverworts. By consuming decaying organic matter and fungi, they facilitated nutrient cycling and soil formation.

This role as “ecosystem engineers” helped create the conditions necessary for more complex plant life to flourish. Their activity broke down organic material, which contributed to the development of the first terrestrial soil structures. This process predated the migration of vertebrate ancestors onto land, marking millipedes as crucial actors in the initial greening of the continents.

When Did Millipedes Develop Chemical Defenses?

Modern millipedes are well-known for their ability to secrete chemical deterrents to ward off predators. The study suggests that this evolutionary trait was not present at the origin of the class but appeared much later. Researchers estimate that the chemical defense mechanism evolved approximately 261 million years ago during the Middle Permian period.

This timing coincides with broader evolutionary trends in the Permian, where increased predation pressure likely drove the development of specialized survival strategies. Most of the extant millipede orders—the biological classification below class—were already established by the Late Jurassic period, between 160 million and 145 million years ago.

Key Findings in Millipede Evolution

• Land Colonization: Occurred roughly 460 million years ago, 80 million years before vertebrate ancestors.
• Fossil Discrepancy: The genetic timeline predates the oldest known physical millipede fossil by 35 million years.
• Chemical Defense: Defensive secretions evolved about 261 million years ago in the Middle Permian.
• Ecological Impact: Early millipedes were primary decomposers that helped build the first terrestrial soil ecosystems.

This research provides a more precise framework for understanding the timeline of terrestrial life. By identifying the origin points of these arthropods, scientists can better map the sequence of events that allowed life to transition from aquatic environments to the complex terrestrial habitats found on Earth today.