The Cambrian period, which began around 518 million years ago, is a fascinating time in the history of life on Earth. It was a period filled with strange creatures, like Hallucigenia and Wiwaxia, but it was also a transformative time for the early fish.
Before the Cambrian, the oceans were mostly home to filter feeders that collected plankton. These organisms lived a fairly calm life, but as predators emerged, life became much more challenging for smaller creatures like fish. Early fish needed to evolve quickly to survive.
Scientists discovered fossils of Myllokunmingiids in China, the oldest fossils resembling fish. Among them is Haikouichthys, a tiny creature measuring just an inch long. This early fish had a distinct body structure, but unlike modern fish, it didn’t have a jaw or all the fins we are familiar with today.
Recently, a study published in Nature revealed something unexpected about Haikouichthys. Instead of the usual two eyes, it had four! Researchers found that it had two larger eyes on either side of its head, along with two smaller eyes in the middle. These smaller eyes contained melanosomes, which help in light detection and color perception.
Author Peiyun Cong from Yunnan University shared that they were surprised to discover these smaller, fully functional eyes. This adaptation likely gave Haikouichthys a wider field of vision, helping it evade predators more effectively. The second set of eyes might have also played a role similar to the pineal gland in modern species, which helps regulate sleep by responding to light.
This finding raises deeper questions about ancient creatures and their experiences. Fish today are often thought of as simple beings, detached from complex emotions. But there’s a growing body of research suggesting otherwise. Studies indicate that fish have cognitive abilities, can experience pain, and form social connections.
Imagining that Haikouichthys had emotional depth—as suggested by its unique eye structure—challenges our view of fish. If we can picture these creatures grappling with their existence, we might treat them with more empathy today.
Ultimately, the four eyes of Haikouichthys serve as a reminder of the complexities of life on Earth. Just like us, these tiny fish faced dangers in a world filled with uncertainty.
For more about modern marine life and fish sentience, you can visit Vox’s article on the subject.
