Creating Their Own Light for Over 540 Million Years

A new study reveals that animal bioluminescence dates back over 540 million years, with octocorals representing the earliest known lineage to evolve this trait.

Since I was 5, I always pictured myself studying animals and traveling all around the world. At age 10, I became obsessed with the study of evolution. How cool it was that all life on Earth evolved from the same organisms? That we all had a common ancestor? Slowly but surely, I started reading more and more about paleontology. Although I graduated from higher education researching vertebrate species, I always had a sweet spot for fossil plants and invertebrates.

And then, I met my husband, a coral reef enthusiast. So naturally, I started paying more attention to this fascinating world, especially where it meets paleontology. Not that doing a PhD near the Great Barrier Reef didn’t help!

But there was something that always fascinated me beyond measure. We were visiting the Colombian Caribean on a little island when they invited us to see the night bioluminescence. They got us under the beach deck and asked us to move our hands energetically. Our hands seemed to be on fire. Our moves triggered organisms in the plankton, and light surrounded us in every move we made. It was magical.

Of course, the paleontologist in me kept thinking about how and when bioluminescence first occurred. Surprisingly, I woke up to a research paper on the topic. What did the authors have to say?

When we think of animals that glow, fireflies and deep-sea creatures might come to mind. However, bioluminescence—the ability of living things to produce light—is far more ancient than we previously thought. According to a recent study led by Dr. Danielle M. DeLeo, from the Smithsonian’s National Museum of Natural History, this mind-blowing trait first emerged in animals over 540 million years ago, nearly 300 million years earlier than we previously estimated. What I love the most about science is how we are always learning more and more!

This discovery is groundbreaking because it doesn’t just tell us about the distant past; it sheds light (pun intended) on the evolution of animals, their behaviors, and their adaptation to changing environments. So, let’s dive into the details and find out how scientists uncovered this ancient glow.

Bioluminescence is a fascinating trait. From deep-sea creatures using it to communicate or hunt, to fireflies lighting up warm summer nights to attract mates, it’s something that sparks curiosity and wonder. Yet, for all its beauty, the origins of bioluminescence have remained a mystery.

Until recently, the earliest record of bioluminescence in animals dated back to around 267 million years ago, in a group of tiny marine crustaceans known as ostracods. However, the new study has completely transformed our understanding of when bioluminescence first appeared in the animal kingdom. The researchers found evidence that octocorals — marine invertebrates that include soft corals, sea fans, and sea pens — had this glowing ability as far back as 540 million years ago.

Decoding the Origins of Bioluminescence

How did the researchers determine that octocorals had bioluminescence so long ago? It all started with an evolutionary tree, which is a map of relationships among species based on their genetic data. This evolutionary tree provided the framework for the study. Using genetic information from 185 species of octocorals, the researchers could trace back the evolutionary history of these creatures.

Next, they placed two fossil samples with known ages within this evolutionary tree. By matching the fossils’ physical features to specific branches in the tree, they could estimate when various octocoral lineages began to split apart. This method, combined with a series of statistical techniques called ancestral state reconstruction (I still remember teaching this to my grad students… fun times), allowed the scientists to infer when bioluminescence likely originated.

The results were astonishing. They found that the common ancestor of all octocorals, living over 540 million years ago, was very likely bioluminescent. This pushes back the oldest record of bioluminescence in animals by almost 300 million years. It also suggests that the trait played a significant role in the evolutionary success of octocorals.

Preserving a Glowing Legacy

Why is this discovery important beyond the “wow” factor? Understanding the origins of bioluminescence can help scientists learn more about its role in animal behavior and communication. Bioluminescence could have been used for many things, like attracting mates, confusing predators, or hunting prey. Knowing when it emerged helps us understand how animals adapted to their environments throughout history.

But there’s another reason why this study matters. Octocorals, like many marine creatures, face threats from climate change and human activities like fishing and oil drilling. These ancient animals, with their remarkable ability to create their own light, are part of our planet’s unique and irreplaceable biodiversity. If we continue to harm their habitats, we risk losing more than just fascinating creatures — we risk losing a part of Earth’s natural history. And once it’s gone, it’s gone forever.

This new study reminds us that the story of life on Earth is vast, interconnected, and, at times, literally glowing. As we move forward, we need to remember the importance of preserving this legacy, one that has been illuminating the world for over 540 million years. It’s up to us to ensure it keeps shining.