Human Vision Evolved to See Through ObjectsSo many of our superheroes are animal-themed because we perceive non-primates as having remarkable powers. Ants have their super-strength, bats have flight and sonar, and canines have sharp teeth and the ability to detect an open bag of kibble from half a mile away. But a recent study reveals that, from the perspective of the animal kingdom, humans have a superpower of our own: "x-ray" vision.Researchers at Rensselaer Polytechnic Institute and California Institute of Technology have studied the advantages of various placements of two eyes on an animal's body, which can go beyond mere depth perception:
Most animals—fish, insects, reptiles, birds, rabbits, and horses, for example—live in non-cluttered environments like fields or plains and have eyes located on either side of their head. These sideways-facing eyes give an animal panoramic vision—the ability to see in front and behind itself. Humans, primates, and other large mammals like tigers, however, have eyes pointing in the same direction. These animals evolved in cluttered environments, such as forests or jungles. Because of their forward-facing eyes, these animals lose the ability to see behind themselves, but they gain a type of X-ray vision that maximizes their ability to see in leafy environments.
Those two eyes focus on slightly different points, allowing us to visualize the area behind some objects:
Demonstrating this X-ray ability is fairly simple: hold a pen vertically and look at something far beyond it. If you first close one eye, and then the other, you'll see that in each case the pen blocks your view. If you open both eyes, however, you can see through the pen to the world behind it.
Unfortunately, although this ability benefited our tree-dwelling ancestors, cognitive science professor Mark Changizi notes that it is less useful to us in our modern life:
"In today's world, humans have more in common visually with tiny mice in a forest than with a large animal in the jungle. We aren't faced with a great deal of small clutter, and the things that do clutter our visual field, like cars and skyscrapers, are much wider than the separation between our eyes, so we can't use our X-ray power to see through them. If we froze ourselves today and woke up a million years from now, it might be difficult for us to look the new human population in the eye, because by then their eyes might be facing sideways."
Scientists Find Our Eyes Evolved for 'X-Ray' Vision [via Science Blog]