There is almost nothing about a whale's body that we can relate to. They breathe air like we do. They give birth to live young like we do. But the similarities seem to stop there. Their scale, body structure, and environment are all different.
But we do have a point of connection: the eyes. Both humans and whales are mammals, so our eyes are derived from a common ancestor. Not only can we look at whales and they can look back at us, but we know enough about optics to infer their eyes' capabilities from their anatomy. Animal eyes can be imagined as technological systems evolved with biological materials.
"We will make the fairly bold claim that it is sensible to approach eyes in essentially the same way that an optical engineer might evaluate a new video camera," write Michael Land and Dan-Eric Nilsson, the authors of the Oxford University Press treatment of our topic, Animal Eyes.
Their eyes capture light in ways we can understand. Their eyes have a focal length. Their eyes have a maximum resolution.
So, what does the world look like to a whale?
Here's what got me pursuing this line of inquiry. The photographer Bryant Austin makes life-size composites of whales: humpbacks, sperm whales, minkes. The results are sublime. Each fin, each ridge in the skin, seems worth pondering. Austin is especially obsessed with photographing their eyes, and with good reason.
To create these images, Austin thought a lot about what kind of visual system could represent the experience of floating next to one of these creatures. Most whale photographers use wide-angle lenses to capture as much of the whale as possible at longer distances, but he realized that wide-angle lenses do not capture enough data to create high-resolution, life-size photographs of whales.
So, on a very fancy Hasselblad H3DII-50, Austin mounted an 80mm portrait lens with a narrow field of view. The consequences of that decision are startling: Austin has to get within ten feet of the whales, and he has to take many photographs from that distance in order to get enough photographs to stitch together the life-size portrait. In practice, that brought him eye-to-eye with these multi-ton animals time and again.
In his new book about his process, out next week, Beautiful Whale, he describes a moment where he came eye-to-eye with a sperm whale named Scar. "I lowered the camera so that our eyes could meet once again, I noticed his eye moving along the length of my body before returning to meet my gaze," Austin wrote. "As I reflect upon that moment and reconsider the question, 'What does it feel like [to be so close to whales]?' the only word that comes to mind is 'disturbing.'"
Why is it disturbing? Because, as Austin puts it, the whale challenges him "to reevaluate our perceptions of intelligent, conscious life on this planet." This mammal's eye -- lens, cornea, pupil, retina, photoreceptors and ganglion nerve cells -- is a direct passageway into its brain. And when we look at it, Austin can't help but see an intelligence there, a connection to a brain that, perhaps, works enough like ours for us to understand each other.
Coming eye-to-eye with a whale, we know what we see. We know how we see, too. Light passes into our eyes through the cornea, which actually does most of the focusing for our eyes. Then it moves through the aqueous humor, to the lens, which finishing up concentrating the light on the retina. The retina is packed with photoreceptors, the cones, which detect color, and the rods, which do not pick up color but are more sensitive in dim light. Specialized ganglion nerve cells pick up excitations from the light-sensitive cells and filter them for contrast (quite seriously: kind of like hitting the "enhance" button in Instagram). This is a wonderful operation. Leo Peichl at the Max Planck Institute for Brain Research, gave a great illustration of how important the ganglions' processing is.
"The ganglions sort of throw away the information about absolute light intensity," Peichl told me. "That's why we can read a book or newspaper at bright sunlight or candlelight, even though at bright sunlight, the black of the letters emits more light than the white paper would in candlelight." In either situation, you see black letters on white paper, even though the raw unfiltered light information is vastly different. (Though obviously, you remain aware that it is brighter outside at noon than next to a candle light.)
Our vision is best where there are the densest collections of all these specialized vision cells. In humans, that's an area called the fovea. We are a weird baseline from which to examine other eyes because we have extraordinarily sharp vision, the sharpest among mammals. Only eagles and hawks can top the discriminating performance of our eyes. We may long to see like cats at night, but our maximum visual acuity (in good light) is many times better than theirs. And bees, just as an example from outside mammalia, have the equivalent of 20/2000 vision. They see with 100 times less visual acuity than we do.
Compared with most mammals (I swear we'll get back to whales in a moment), humans have remarkable color vision as well. We can distinguish big chunks of the colors in the green, red, and blue parts of the spectrum. It's not nearly as impressive as some visual systems, which can detect other parts of the electromagnetic spectrum, but when it comes to mammals, humans and some other primates are living the technicolor dream. Color vision is trickier than it seems at first. It's not that we see blue with blue photoreceptors and red with red photoreceptors. "What provides the sensation of color is our ability to compare how much light each receptor class collects," Duke's Sonke Johnsen, author of the book Optics for Biologists, told me. The leaves of a vine reflect more green light at our eyes than the red bricks on which they are climbing. So our green photoreceptors pick up more light where the leaves are and our red photoreceptors pick up more light where the brick is.
Most mammals have dichromatic vision. They can see color, but they cannot discriminate along the red-green axis. Humans with this relatively rare type of color blindness have a hard time differentiating between red and green, as well as colors close to them like oranges and browns, as one blogger describes it, depending on how saturated and bright the color is.
In general, mammals don't have the best color vision. In part, that's because our ancestors developed trying to see in the dark, not out in the bright sunlight. "There was a time where to be a mammal was to be a small, nocturnal, rodent-like mammal," said Duke's Sonke Johnsen, author of the book, The Optics of Life. Both humans and whales retain the marks of that evolutionary path. "Our color vision is kind of a kluge," Johnsen continued. "If you look at the color vision of birds and reptiles and fish. It's very well put together, nicely optimized. You look at our trichromatic vision, it's really kind of pieced together."