The Woman Who Can See 100 Million Colors

Human perceptions are arbitrary, even accidental outgrowths of the story of our species. They're the invisible variable that shapes everything in our history. Can we change them?

A quick note: today is the day (!) that my new book—FLUKE: Chance, Chaos, and Why Everything We Do Matters—is released into the world. I hope you’ll consider ordering it; it’s my favorite piece of writing I’ve ever produced and it reshaped my entire worldview.

The first chapter is free to read here and here and there’s an adapted excerpt in The Atlantic. I’ve already notified the winners of the signed book contest (congratulations to Kat, Olivia, and Kazuhiko) and thanks to everyone else who filled out the pre-order form!

If you’re interested in using FLUKE for your book club of six or more people, let me know by replying to this e-mail. I’ll do my best to either send you a video message or, if the timings work and I’m available, to drop in and briefly speak to your book club via Zoom.

Finally, here’s a brief little video teaser about Fluke from the folks at Simon & Schuster:

Now, onto today’s actual article…

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The Hidden Variables of Human History

Humans, like all living creatures, navigate the world based on our perceptions of reality.

Ponder our perceptions for more than an instant, however, and it’s clear the way we see the world is skewed, not objective. We can’t see ultraviolet light—butterflies and reindeer can—or infrared light—snakes can—but both forms of light are certainly there. We can’t sense the magnetic fields around us—sharks can—and they’d be lost without them. The platypus—a venomous egg-laying mammal with the bill of a duck, the tail of a beaver, and the feet of an otter that sweats milk out of the pores on its stomach to feed its young—can sense electrical fields.

In fact, with the visible color spectrum, human eyes can sense about one in ten trillion electromagnetic waves that exist. That’s it.

It’s pretty disorienting to grapple with the revelation that our version of reality is…not reality. But that’s obviously true.

How would human history have unfolded differently if we could only see in black and white? What if human eyesight were as sharp as eagles, or our smell as acute as a bloodhound? Or, what if we could see 100 times more colors than we do? History would have unfolded radically differently. But how? And why does it matter?

The answer to those questions requires an astonishing, mind-bending journey to meet two astounding living creatures: the peacock mantis shrimp and a doctor who lives in Northern England—a woman with magnificent eyes the rest of us can only imagine.

Accidental Vision, Arbitrary Eyes

The way we see the world is the byproduct of a series of randomized evolutionary experiments. The ones that stuck around were those that, on average, helped our ancestors survive long enough to have children. We rarely consider that our lens on the world is unique; no other species sees the world exactly like us.

With three types of photoreceptors in our eyes (red, green, and blue), humans are trichromats. Dolphins and whales are monochromats, navigating the oceans in black and white. Most non-human mammals—including our beloved dogs—are dichromats, so they see the world a bit more like a human who is red-green colorblind. Most birds, fish, reptiles (and probably dinosaurs) have four kinds of photoreceptors, allowing them to see ultraviolet light, so they’re tetrachromats.

Bees are trichromats, but they’ve swapped out the ability to see red for the ability to see UV light. Some primates, including spider monkeys, have vision that differs by sex, in which females have three photoreceptor types, compared to males that have two. (If you want to learn how the evolution of human eyesight was profoundly diverted by figs…read Fluke).

So far, we’ve discussed creatures with between one and four kinds of photoreceptors. But there’s one species that doesn’t mess around with such amateurs.

Do not mess with the peacock mantis shrimp

Here I shall take a brief, but awe-inspiring, detour, for we must meet an unexpected character in our story, the peacock mantis shrimp, which aren’t shrimp but are cousins of crabs and lobsters. Literary descriptions can’t do this amazing creature justice, but I shall be foolhardy and attempt one nonetheless.

Its shell is a psychedelic kaleidoscope of color, with a shimmering blue, green, and orange lobster-style back converging toward its head, which is adorned with bug-eyed baby blue eyes perched atop a stumpy stalk. Appendages sprout out of its head in a whimsical, downward drooping swoop, like the crustacean version of a Fu Manchu moustache. Its underbelly is a bright, fluorescent shock of red.

See, I wasn’t exaggerating. This thing is weird.

The peacock mantis shrimp is sadly less famous for its color vision and more known for its punch. And what a punch it is. I digress, but it is a worthwhile digression, because this is, by far, the most forceful punch in the animal kingdom.

The club of the peacock mantis shrimp accelerates faster than a bullet being shot out of a gun, smashing its prey with such force that it produces a shockwave by unleashing vapor-filled bubbles, which stuns the unfortunate victim, doubling the effect of the blow. In an effect known as cavitation, the club’s velocity is so great that the water around the mantis shrimp’s weapon briefly vaporizes, temporarily reaching 8,500 degrees Fahrenheit, nearly the same temperature as the surface of the sun. The club can split human thumbs and break aquarium glass.

My advice is this: Do not mess with the peacock mantis shrimp.

But what’s most astonishing is the evolutionary accident of its vision, which is unlike any other species. The peacock mantis shrimp has the most elaborate visual structures known to exist in the universe.

Rather than one, two, three, or four photoreceptors, the peacock mantis shrimp has twelve.

This unleashed rampant scientific speculation: what is it like to see the world as a peacock mantis shrimp?

We have no idea. But some experiments have been disappointing. In one study in which they got peacock mantis shrimps to try to differentiate shades of color (imagine trying to do that) they performed slightly worse than humans. But there’s a lot of lingering mysteries, and scientists are baffled by the vision of the peacock mantis shrimp. We have no idea whether they perceive the world in such an alien way that we can’t even imagine it.

“Alright, Mr. Animal Trivia,” you might be shouting at your screen by now. “Thanks for all the weird factoids. But what does this mean for us?”

Well, here’s where the strange mysteries of perception overlap with our world…

The doctor who can see 100 times more colors than you

How close are we to seeing the world differently? Could we have more photoreceptors?

For reasons too technical to go into here, take my word for it that it is genetically possible for women, but not men, to be tetrachromats rather than trichromats. Many so-called “weak tetrachromats” have previously been identified, in which those women have genetically unusual eyes, but their vision is functionally the same as the rest of us. Intriguing, yes, but their perception of the world doesn’t radically differ from everyone else.

That led Dr. Gabriele Jordan of Newcastle University to launch a search for a genetic unicorn: a strong tetrachromat, someone who actually perceives the world differently from the rest of us. And, after a series of tests and years of studies, she finally found one. She’s been tested rigorously and, each time, she can identify color gradients that should be invisible to her because they are invisible to all other humans.

This extraordinary woman, known to science as “cDa29,” has decided to stay anonymous (probably wise—podcast hosts can be like vultures) but we do know that she’s a doctor who lives in northern England.

According to the best scientific evidence so far, it’s hypothesized that she can see roughly one hundred times more colors than the rest of us. The average person is able to perceive about a million shades of color. For cDa29, that number is one hundred million.

In a paper describing the import of their findings, Dr. Jordan can only speculate as to what it might be like to see the world through those eyes. Perhaps, she suggests, that extra specificity in vision can help early detection of disease, but the other benefits might be wasted, since cDa29 lives in a world full of people totally unlike her:

On the basis of anecdotal evidence we have speculated that there may be signals in the skin tone of conspecifics that are linked to health or disease. In such cases early detection will be advantageous.

Will a potential tetrachromat be a more successful artist? If she uses her color palette veridically [accurately] to render her sensations, then it is not clear how she can communicate the added richness of her private gamut to those who live in an impoverished perceptual world.

The art produced by someone with the eyes of cDa29 could be exquisite, but there would be nobody to appreciate it, blinded as we are by our inferior color vision.

Technology, change, and the possibility of new senses

Throughout history, humans have been constrained by what we can sense. This is true for every creature, as each living being inhabits an umwelt (the subjective perceptual world they are able to experience based on their evolved senses).

As the neuroscientist David Eagleton memorably put it in his TED talk:

“Imagine that you are a bloodhound dog. Your whole world is about smelling. You’ve got a long snout that has 200 million scent receptors on it, and you have wet nostrils that attract and trap scent molecules…Everything is about smell for you.

So, one day, you stop in your tracks with a revelation. You look at your human owner and you think, ‘What is it like to have the pitiful, impoverished nose of a human? How can you not know that there’s a cat 100 yards away, or that your neighbor was on this very spot six hours ago?’

Because we’re humans, we’ve never experienced that world of smell, so we don’t miss it.”

But unlike other creatures, we are able to change our senses, strengthening them with technology.

For example, in the ancient past, humans could only see five planets. (This, by the way, is one of the main reasons why we subdivide our lives into seven-day weeks; the ancient Romans believed in the power of astronomy, and figured it was wise to divide time by the five visible planets—plus the sun and the moon—which makes seven).

More than a thousand years later, Galileo used the telescope to see far beyond any other human prior to him, unleashing fresh knowledge and a new way to sense the universe. In the ensuing centuries after the scientific revolution, we’ve not just augmented our umwelt, harnessing everything from X-rays to radio waves, but we’ve also made it possible to restore senses that have been lost—with fresh, mind-bending technologies.

That raises the obvious question: if we can restore normal human senses to those who don’t have them, can we create new senses? This is where Eagleton’s extraordinary research comes in, with experiments showing that the brain is remarkably flexible in processing new sensory stimulations and making sense of them in useful ways.

One study demonstrated the effectiveness of having a pilot wear a vest that provides real-time information—pitch, yaw, and orientation—of a drone they’re flying. Without thinking, the vest provides information that the brain is able to immediately interpret, giving the pilot a far more accurate sense of how the drone is moving, even in fog, or darkness, or over a significant distance.

Eagleton’s research is also being used to develop a way to sense “friendly” troops on a battlefield, such that you don’t accidentally kill a soldier from the same army because your brain can literally sense where they are, just by wearing a vest that provides real-time location information. The same technology is being adapted for use with blind people, allowing them to sense people around them at all times. It’s not the same as vision, but it’s a different sense than the ones our bodies evolved to process—seamlessly incorporated into our remarkably flexible brains.

This scientific wizardry raises an astonishing notion: perhaps we can, someday, genuinely experience the world like cDa29, or, even more bizarre, engineer a technology that allows us to better imagine what it’s like to be a peacock mantis shrimp. These are extraordinary possibilities that raise questions of ethics, the limits of technology, and how our increasing fusion between our physical bodies and our scientific creations pose new challenges to what it means to be a human.

But what I find most extraordinary to ponder isn’t about what lies ahead. Instead, it’s the arbitrary series of events that led to the evolution of our senses, one possible umwelt that we all live within, which has profoundly shaped who we are and everything our species has ever done.

Thank you for reading The Garden of Forking Paths. I hope you’ll consider ordering Fluke! I was on the show “Morning Joe” on MSNBC yesterday morning speaking about the more current affairs-related angles of Fluke. You can watch that interview here: