Israeli Researchers Discover Turtles and Humans Share a Surprising Visual Ability

Sometimes a fresh perspective can entirely change how an object appears. Look at a simple glass of water up close. The light refracts through the transparent liquid and its container in an entirely different way than it does if you observe the cup from above or from far away. Somehow, your brain still recognizes what it is, no matter how the shadows, lighting, and angles distort it.

This ability to make sense of what’s in front of your eyes despite changes in angle, light, and position was once thought to be limited to higher mammalian brains. However, a recent Tel Aviv University study, published in Science Advances, challenges this idea. In the study, researchers tracked brain activity in turtles and found that they can respond to unexpected visual stimuli in a stable and consistent way, despite changes in viewpoint.

A Common Ancestor
Mammals and reptiles are believed to have evolved from a common ancestor that left the water and adapted to life on land at least 320 million years ago, according to The Times of Israel. This ancestor likely had a brain with a three-layered cerebral cortex and more advanced visual abilities than earlier aquatic life.

Over the next 320 million years, mammalian brains evolved to have a six-layered cortex, while their reptilian relatives retained a simpler three-layered structure.

An Evolutionary Ability
The Jerusalem Post reported that scientists had long thought that advanced visual processing was a skill that had evolved later alongside mammalian brains and was limited to animals with more complex cerebral cortices.

A team at Tel Aviv University, led by Milan Becker, Nimrod Leberstein, and Mark Shein-Idelson, set out to challenge this idea. Researchers tracked the eye movements and brain activity of turtles as the animals responded to both expected and new visual stimuli. The data revealed that turtles can process these stimuli in a stable way, even as they move their heads or eyes and perceive them from different angles.

The research demonstrates that this visual processing skill likely emerged much earlier than previously thought and that humans and turtles share this ability.

A Useful Skill
Researchers explained that this skill helped Earth’s early terrestrial creatures visually distinguish between changes in their environment, including the appearance of predators, and visual changes caused by their own movements.

“Imagine you’re an animal on land, looking around, and there’s a predator,” Shein-Idelson explained to The Times of Israel. “This predator falls on some part of the retina. You locate it in a particular direction. Now, you move your eye or your head, and the [image of the] predator falls on a different part of the retina. Is it the same predator? The retina changes with every shift of your gaze, but the objects in the world don’t necessarily. So the animal must integrate the object and the environment into a coherent understanding that is independent of eye movements. This is a major challenge when you are on land and rely on vision,” he added.

It’s clear how this ability would have given Earth’s early land creatures a significant evolutionary advantage, just as it helps humans today make sense of the world around them. Some of the human brain’s most helpful traits may be deeply rooted in a shared evolutionary past.