Marine mammals, such as whales and dolphins, are gifted in terms of deep diving and like most abilities today, this stems from great evolutionary transitions that help them live in oceans and adapt to a changing world.

A new study from researchers at the University of Toronto shed light on how whales' early ancestors evolved from on-shore living to deep-sea foraging, suggesting that they might have visual systems that quickly adapted to life in water to adapt to the dark.

Whales Share the Same Ancestors As Hippos That Can See in the Dark

According to Science Alert, the first mammals that returned to see had eyes specifically designed to see in the dark, deep ocean. These mammals were collectively known as cetaceans, such as whales, dolphins, and porpoises, who all came from a common ancestor with a powerful underwater vision about 35 million years ago.

Aside from these marine mammals, whales shared the same ancestor as the four-legged land mammal hippopotamus about 50 million years ago. Although both mammals have aquatic lifestyles, only the whales further evolved to have the ability to dive deep into the ocean.

There was a great mystery about when they transitioned from being land mammals to becoming marine mammals and how quickly they developed the ability to see in the deep sea. But the new findings of the study indicate that whales transitioned shortly after returning to the sea.

Researchers studied the fossils of ancient whales to get answers to these questions and focused on the rhodopsin protein found in the eyes of the whales and their ancestors.

Eye Protein in Whales Enables Them to See in the Dark to Dive Deep in the Ocean, Study Reveals
(Photo : Unsplash/Seiji Seiji)
Eye Protein in Whales Enables Them to See in the Dark to Dive Deep in the Ocean, Study Reveals

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Rhodopsin Protein in the Eye Lets Whales See in the Deep, Dark Sea

Professor Belinda Chang from the University of Toronto said in a news release that the evolution of whale diving has always been a long-standing question of deep-sea foraging. Their findings showed that this ability evolved even before toothed and baleen whales diverged.

Together with Dr. Sarah Dungan, they described their experiments, computational analysis and results in the study titled "Ancient Whale Rhodopsin Reconstructs Dim-light Vision Over a Major Evolutionary Transition: Implications for Ancestral Diving Behavior," published in the Proceedings of the National Academy of Sciences.

Dungan used robust data science models of rhodopsin proteins from different living whales and other cetaceans, which revealed a gene sequence that shows rhodopsin in the common ancestor of living whales. She then experimented with it in lab-grown cells to "resurrect" the rhodopsin protein and tested it on some purified samples.

They found that the resurrected protein makes early whales more sensitive to blue light penetrating the deep ocean like no other. Its biochemical signatures suggest that they have retinas that could rapidly respond to changes in light levels. Whale ancestors eventually evolved into many kinds of whales, and as separate species evolved, they established ecological niches at different levels.

Given these findings, they plan to resurrect the ancestral proteins that transmit rhodopsin light signals to understand the neurological adaptations involved in deep diving. They hope it will provide new evolutionary learnings to gain greater insight into how animals adapt to a changing world.

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