Imagine the deepest, darkest corners of our planet, where sunlight never reaches, yet a mesmerizing glow persists, lighting up the shadows. This is bioluminescence, a phenomenon so captivating that it has evolved independently at least 94 times throughout Earth’s history. But here’s where it gets even more astonishing: scientists have now traced its origins back a staggering 540 million years, to a class of corals called Octocorallia lurking in the Cambrian ocean. That’s more than double the age of the previous record-holder, a tiny crustacean that lived 'just' 267 million years ago. And this is the part most people miss—this discovery not only rewrites the timeline of bioluminescence but also raises questions about why so few species retain this ability today. Could it be a lost art of the ancient seas? Or is there something more mysterious at play?
Bioluminescence is nature’s own light show, a chemical reaction mastered by organisms to produce their own glow. From luring prey to warding off predators, its uses are as varied as the creatures that wield it. But how did it all begin? Marine biologist Danielle DeLeo and her team at the Smithsonian Institution turned to octocorals—ancient, soft-skeleted corals with an eightfold symmetry—to find answers. These creatures, some of which glow only when disturbed, seemed like the perfect candidates to uncover bioluminescence’s origins. Using a detailed octocoral family tree published in 2022 and genetic data from 185 taxa, the researchers traced the lineage of bioluminescent species back to their common ancestor.
Through a technique called ancestral state reconstruction, they analyzed living bioluminescent octocorals—including five newly discovered types—to infer whether their ancestors shared this trait. The results were consistent: bioluminescence emerged around 540 million years ago, during the Cambrian period, when multicellular life was still in its infancy. But why then? The presence of marine invertebrates with light-detecting eyes at the same time suggests an intricate interspecies dance, possibly driving the evolution of this ability. But here’s the controversial part: if the common ancestor of today’s octocorals had bioluminescence, why did so many species lose it? And how?
This question opens a Pandora’s box of ecological mysteries about the Cambrian ocean. Was bioluminescence once a widespread survival tool that became obsolete? Or did it serve a purpose we’ve yet to fully understand? The study, published in Proceedings of the Royal Society B Biological Sciences, is just the beginning. The next step is to unravel how and why this trait faded over time, potentially shedding light on the ancient ocean’s secrets.
And if you’re as fascinated by bioluminescence as we are, here’s a glowing opportunity: subscribe to our free Spark newsletter today and you could win a $10,000 vacation, including a bioluminescent night kayaking tour! Sweepstakes end on 11 December 2025 at 11:59 PM ET. Full details are available on our website. So, what do you think? Is bioluminescence a lost treasure of the ancient seas, or is there more to the story? Let us know in the comments—we’d love to hear your thoughts!
