Environment Life

Vertebrates’ ancestors may have had four eyes, study finds

Fahad Redha

March 17, 2026
4 min read

Vertebrates’ ancestors may have had four eyes, study finds

The earliest ancestors of vertebrates, animals with a backbone including us, may have had two pairs of eyes, a study published in Nature has found. The remnants of the additional eyes persist in our brain to this day as the pineal organ, deep within our brain, that regulates sleep cycles but no longer creates images.

The earliest vertebrates “had eyes like we do, but not just eyes like we do,” the study’s co-author, Jakob Vinther at the University of Bristol told New Atlas in an interview. “They had four eyes,” he added, saying that it is “quite amazing to think that our ancestors were swimming around in the ocean like half a billion years ago, and used four eyes to see the world. They probably had a much greater field of view.”

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China’s Kunming region is known for an exceptional preservation of fossils from the Cambrian period (540–485 million years ago) There, specimens were found of two myllokunmingid species, some of the earliest vertebrates known to science. Both species dated back 518 million years ago and had well preserved remains that revealed four black spots, two larger spots on the sides of the head and a second pair between them.

The researchers once thought that the second pair were nasal capsules but this contradicts other research which shows that these animals had only a single nostril. Under an electron microscope, the presence of melanosomes, tiny organelles that contain melanin. Melanin determines the colour of eyes but also absorbs light to create an image.

Before this, the oldest known melanin was no older than the Carboniferous period, 300 million years ago. An impression of a lens was also found inside the organs, suggesting that the animals had two big eyes on the side and two smaller ones on the top, according to Vinther who added that “both of them were camera eyes.”

The paper suggests that the four eyes evolved during pressure from the environment including predators, with the researchers believing that these animals were at the bottom of the food chain. As things changed, the second pair of eyes could have evolved into a non-sensory organ knwon as the pineal gland that produces melatonin and regulates sleep cycles.

The fins could help “paint a clearer picture of the early stages of vertebrate evolution,” according to Elias Warshaw, a paleobiologist at University College London, who wasn’t involved in the study. Warshaw supports the findings, adding that “the hypotheses presented within the paper are thoroughly tested, and the results are interpreted reasonably”.

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