What did the old whale see? | Hakai Magazine

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It is almost impossible to know how extinct animals behaved; There is no Jurassic Park where we can watch them hunt, mate or dodge predators. But an emerging technique is giving researchers a physiological cipher to decipher the behavior of extinct species by reconstructing and analyzing the proteins of extinct animals. This molecular necromancy can help them understand features not preserved in the fossil record.

In the most recent example of this technique in action, scientists led by Sarah Dungan, a graduate student at the University of Toronto (U of T) in Ontario, have revived the visual pigments of some of whales’ earliest ancestors. The work gave Dungan and her colleagues new insight into how proto-cetaceans would have lived just after a crucial evolutionary turning point: around 55 to 35 million years ago when the animals that would eventually become whales and dolphins gave up their terrestrial lifestyle to return to the sea.

Dungan’s fascination with whale evolution began when she was eight years old. As a child, she loved spending time in the water and learning about marine biology. Her father casually told her that the ancestors of modern whales once lived on land. The idea that an animal could transform itself from a life without water to a life outside of water stayed with her. Learning about the evolutionary transition of modern whales — from ocean to land and back again — “I was totally blown away,” she says. “The newspaper is the end of a story that began when I was very young.”

in the 2003, researchers at the U of T pioneered a technique to assemble the ancient visual proteins of extinct animals. You’ve applied the technique across the animal kingdom and learned more about how extinct species viewed the world. However, studying extinct whales is particularly interesting because the transition from land to ocean has changed the animals’ visual ranges.

In this study, the researchers compared rhodopsin, the visual pigment responsible for twilight vision, from the animals that made the transition from land to ocean. They focused on the first whale, which lived 35 million years ago and probably swam with powerful muscles in its tail, and the first whippomorph (one of a group of animals that includes whales and hippos), which lived 55 million years ago lived.

Scientists have not yet discovered the fossils for the two extinct species. By the way, you can’t even tell exactly what species it is. But Dungan’s technique can also infer ancient protein sequences without this information. The approach follows the evolutionary breadcrumbs left in the proteins of modern animals to find out what the ancient forms would have looked like, even without the bones of the species itself. By comparing the putative proteins of the first whippomorph and the first whale, we can the scientists recognize the subtle differences in their eyesight. These differences in vision could reflect differences in the animals’ behavior.

“There is a limit to what you can learn from fossil evidence,” says Dungan. “But the eye is a window between the organism and its environment.”

Using an evolutionary tree and the known rhodopsin structures of modern whales, Dungan and her team built a model to predict the ancient animals’ variants. They made the visual pigments in the laboratory by genetically modifying cultured mammalian cells and tested the light to which they are most sensitive. The scientists found that the extinct whale was likely more sensitive to blue light wavelengths compared to the ancient whippomorph. Blue light penetrates deeper into the water than red, so modern deep-sea creatures, below fishes and whales, have blue-sensitive vision. The find indicates that the extinct whale felt comfortable in the deep sea.

The scientists also found that the rhodopsin version of ancient whales adapted quickly to darkness. Modern whales’ eyes adapt quickly to dim light, helping them move between the bright surface where they breathe and the dark depths where they forage. That realization is “what really sealed the deal,” Dungan says.

Based on their findings, the scientists believe early whales likely dived into the ocean’s twilight zone, between 200 and 1,000 meters. When diving, eyesight was vital. Ancient whales couldn’t echolocate like dolphins, so they relied more on sight.

The finding is surprising, says Lorian Schweikert, a neuroecologist at the University of North Carolina Wilmington, who was not involved in the study. She thought the first whales stayed near the surface. “Now we started at the bottom,” she jokes, Allusion to Drake’s hit song.

Schweikert says that studying ocular physiology is a reliable way to infer an animal’s ecology because visual proteins don’t change much over time. The rare changes almost always correlate with environmental shifts.

The key takeaway from Dungan and her colleagues’ work, says Schweikert, is that it further clarifies the order in which extreme diving behavior in whales evolved. The rhodopsin research builds on previous work that painted a similar picture. in one previous studyresearchers reconstructed ancient myoglobin and showed that early whales “charged” the oxygen supply to their muscles while holding their breath – further evidence that they were capable divers. Another studythis time on ancient penguins, showed that their hemoglobin evolved mechanisms to manage oxygen more efficiently as the birds made their own transition to marine life.

Dungan and her colleagues are now channeling their Ouija molecular board to revive rhodopsin from the earliest mammals, bats and archosaurs. This will help them understand how nightlife, digging, and flying evolved.

The approach is “just really fun,” says Schweikert. “One tries to look into the past to understand how these animals evolved. I love that we can look at visions to solve some of these problems.”