“In old age we should wish still to have passions strong enough to prevent us turning in on ourselves,” Simone de Beauvoir wrote as she considered how to keep life from becoming a parody of itself, while across the English Channel the ever-sagacious Bertrand Russell was offering his prescription for how to grow old and across the Atlantic the vivacious elderly Henry Miller was distilling the secret to remaining young at heart as a matter of being able to “fall in love again and again… forgive as well as forget… keep from growing sour, surly, bitter and cynical.”

But no one has approached the universal problem of advancing from youth to old age, or the dialogue between the two within a lifetime and across generations, more insightfully, delightfully, and with richer nuance than the great classics scholar and linguist Jane Ellen Harrison (September 9, 1850–April 15, 1928), whose extraordinary life I came upon in Francesca Wade’s altogether scrumptious book Square Haunting: Five Writers in London Between the Wars (public library) and whose work revolutionized the modern understanding of Ancient Greek culture by upending millennia of patriarchal revisionism with Harrison’s discovery of an entire class of “matriarchal, husbandless goddesses” central to community life and ritual.

In her sixty-fifth year, as World War I was breaking out, Harrison reflected in a letter that “work & friendship come to be the whole of life.” As the ledger of her life grew thick with decades, she never lost her intellectual vivacity, her lively intergenerational friendships, her active engagement with the ever-pulsating world of scholars and artists — in no small part because of the life and love she shared with her significantly younger partner: the poet, novelist, and translator Hope Mirrlees.

Hope Mirrlees and Jane Ellen Harrison

That same year, Harrison was startled to hear one of her young, talented colleagues at Trinity College proclaim that “no one over thirty is worth speaking to.” With her winking intelligence, she observed:

This is really very interesting and extraordinarily valuable. Here we have, not a reasoned conclusion, but a real live emotion, a good solid prejudice, a genuine attitude of gifted Youth to Crabbed Age. It is my business to understand and, if I can, learn from it. Give me an honest prejudice, and I am always ready to attend to it.

In a sentiment that ought to be the ultimate manifesto for intellectual and emotional humility, direly needed in our own time, she adds:

I am long past blame and praise, or, rather, I am not yet ready for them; there is so much still waiting to be understood.

And so she set out to do just that in an entertaining, existentially profound essay titled “Crabbed Age and Youth,” published in her 1915 essay collection Alpha and Omega (public library).

Harrison considers the rudiments of maturity and what makes us who we are by examining the “relations between fairly mature youth and quite early middle age,” defining the latter as “anything completely or hopelessly grown up — anything, say, well over thirty,” winking at the relativity of age with the memory of a time when a person of fourteen appeared to her child-self “utterly grown up.” Reflecting on the young scholar’s remark, and noting in herself with even greater alarm a similar “counter-prejudice” against youth, she observes:

The reasons by which people back up their prejudices are mostly negligible — not reason at all at bottom, but just instinctive self-justifications; but prejudice, rising as it does in emotion, has its roots in life and reality.

She notes that while there is often great friction between the young and the old, this friction can, “if rightly understood and considerately handled on both sides, take the form of mutual stimulus and attraction” — for it most often springs from a lack of understanding of each other’s state of being and frame of reference. The source of this friction is also the source of the exquisite complementarity of the two life-stages:

Youth and Crabbed Age stand broadly for the two opposite poles of human living, poles equally essential to any real vitality, but always contrasted. Youth stands for rationalism*, for the intellect and its concomitants, egotism and individualism. Crabbed Age stands for tradition, for the instincts and emotions, with their concomitant altruism. (*Note: Due allowance of course being made for the anti-intellectual reaction in the present generation.)

[…]

The whole art of living is a delicate balance between the two tendencies. Virtues and vice are but convenient analytic labels attached to particular forms of the two tendencies. Of the two, egotism, self-assertion, are to the youth as necessary — sometimes, I sadly think, more necessary — to good living than altruism. Moreover, the egotism of youth is compulsory, inevitable, and equally the altruism of age is ineductable.

Illustration by Maurice Sendak for poet Robert Graves’s little-known children’s book.

A century before the selfing pandemic of social media, Harrison considers the chief handicap of the young — their tendency to “masquerade,” which calls to mind Hannah Arendt’s insight into being vs. appearing and our impulse for self-display, and Walt Whitman’s reflection on what trees teach us about being rather than seeming. She writes:

Acting is sinking your own personality in order that you may mimic another’s. Masquerading is borrowing another’s personality, putting on the mask of another’s features, dress, experiences, emotions, and thereby enhancing your own… Youth, and especially shy Youth, is strongly possessed by the instinctive desire to masquerade.

[…]

Masquerading bores Crabbed Age. Why?

Simply because the impulse to imaginative self-enhancement dies down as soon as liberty to live is granted… Crabbed Age is busy living, not rehearsing, and living, if sometimes less amusing, is infinitely more absorbing. It takes so much out of you.

And yet the old have their own way of oppressing the young, equally alienating to both and equally damaging to the collective mosaic of culture:

It is a waste of time putting up signposts for others who necessarily travel by another, and usually a better, road. Old people are apt to make disastrous confusion between information that can be accumulated and conveyed, that is identical for all time, that is knowledge, and experience, that which must be lived and cannot be repeated.

But Old Age does worse than that. In trying to impose its experience as a law to youth it sins not only through ignorance, but from sheer selfishness. Parents try to impose their view of life on their children not merely or mostly to save those children from disaster — that to a certain extent and up to a certain age we must all do — but from possessiveness, from a desire, often unconscious, to fill the whole stage themselves.

[…]

The truth that it has failed to grasp is a hard one for human nature. This truth is that, in all matters that can be analyzed and known, Youth starts life on the shoulders of Age, and therefore… sees farther and is actually more likely to be right.

Across this divide youth and old age frustrate and bore each other — one excited about everything, especially the masquerade of the self, the other increasingly specialized and outward-focused in its excitations, and at times oppressively so. But eventually, Harrison observes, life intercedes and the young are forced — by falling in love, by creative self-actualization, by some great calamity or illness, by the demands of a career, by the demands of a family — to shed their masks and narrow their locus of concerns, growing more entwined with other selves:

Through any bit of actual work or responsibility, Youth takes a part in life, becomes a real part, instead of claiming a theatrical whole, straight-way Youth mellows, becomes interesting and easier to live with.

In a passage of extraordinary insight into the meat of life, she writes:

Real life — and here comes the important point — real life, as contrasted with life imagined and rehearsed, on the whole compels at least a certain measure of altruism. There are many methods of compulsion, some gentle, some violent. We will consider for a moment only two, and these the most normal.

Normally, in the first place, life itself will lure you, catch you, and marry you, make a father or a mother of you, and your children will soon stop your masquerading, and teach you that you are not the centre of their universe — nay, compel you to revolve round the circumference of theirs. Marriage, through the lure of passion for the individual, compels your service to the race. This great education in altruism is necessarily more drastic and complete for woman than for man.

But suppose you elude the natural lure of life. There is society waiting with its artificial lure — waiting to catch you and make an official of you, a functionary, a thing that is only half or a quarter perhaps yourself, and a large three-quarters that tool and mouthpiece of the collective conscience. How often one has seen a year’s officialdom turn a man’s spiritual hair grey! The gist of all officialdom is not its labels, its honours, but the sacrifice of the individual will; and for this society is always ready, and rightly, to pay a big price. Of course, though there is loss, there is great gain in officialdom as in marriage. Each is a godly discipline by which the young man learns not to be the centre of his own universe.

Illustration by Maurice Sendak for a rare edition of the Brothers Grimm fairy tales.

Recognizing that children are often the most distilled and unalloyed version of all of our adult puzzlements and confusions, she adds:

This being the centre of your own — of course, quite fictitious — universe is best seen in the extreme case of the megalomania of young children, as yet untaught by life. Their own experience is always illuminating.

[…]

At seven years old one cannot analyze, so one must agonize. That is why it is so terrible to be a child, or even a young thing at all. One sees things, feels them, whole. There is no such devastating, desolating experience as to have been at the centre, warm and sheltered, and suddenly to be at the outmost circumference, and be asked to revolve as spectator and sympathizer round a newly-formed centre.

We carry much of that primal self-centeredness, and the grief of its loss, well into young adulthood — a term, and concept, that didn’t exist in Harrison’s era. Eric Berne’s revolutionary framework of the Child, Parent, and Adult ego-states that live in each of us was still half a century away. With her own singular lens on how we become ourselves — and our selves — Harrison writes:

As long as you want to be, and feel yourself to be, the whole of life, as long as you do not specialize and become a functionary, you do not co-operate, you cannot apprehend or be interested in the personalities of others. You are only one of a great chorus, all masquerading, all shouting, “Me, Me—look at ME!” Once you specialize, once you become an actor with a part in life, then you need all the other actors; the play cannot go on without them. Even your part in it depends on them. The me becomes us.

[…]

Far from it being true that specialization narrows the individuality, specialization is almost the condition of any true individualism. Through co-operation the sense of personality is born and nourished… The narrow, tedious people are those who are “living their own lives” and consciously “developing their own individualities” — trying to out-shout the other members of the chorus instead of singing in tune, playing their part as actors in a troupe.

With the kind of lucidity that only conscientious hindsight confers, she paints an image that captures the whole paradox of becoming:

It is one of the tragic antinomies of life that you cannot at once live and have vision… Looking back on life I seem to see Youth as standing, a small, intensely-focused spot, outside a great globe or circle. So intense is the focus that the tiny spot believes itself the centre of the great circle. Then slowly that little burning, throbbing spot that is oneself is sucked in with thousands of others into the great globe. Humbled by life it learns that it is no centre of life at all; at most it is one of the myriads of spokes in the great wheel. In Old Age the speck, the individual life, passes out on the other side, no longer burning and yet not quite consumed. In Old Age we look back on the great wheel; we can see it a little because, at least partially, we are outside of it. But this looking back is strangely different from the looking forward of Youth. It is disillusioned, but so much the richer. Occasionally nowadays I get glimpses of what that vision might be. I get my head for a moment out of the blazing, blinding, torturing wheel; the vision of the thing behind me and without me obscurely breaks. It looks strange, almost portentous, yet comforting; but that vision is incommunicable.

Art by Carson Ellis from What Is Love? by Mac Barnett

Crowning the essay is a wonderfully nuanced definition of age, emanating a kind of wisdom difficult for the ego to nod at but beautiful and necessary:

Anyone who cares passionately for abstract discussion, be his hair never so grey, his hand never so palsied, is in spirit young. I do not say this is an advantage. It is possible to stay young too long. There is a “time to grow old.”

[…]

People ask: “Would you or would you not like to be young again?” Of course, it is really one of those foolish questions that never should be asked, because they are impossible. You cannot be — you that are — young again. You cannot unroll that snowball which is you: there is no “you” except your life — lived. But apart from that, when you rise from what somebody calls “the banquet of life,” flushed with the wine of life, can you want to sit down again? When you have climbed the hill, and the view is just breaking, do you want to reclimb it? A thousand times no! Anyone who honestly wants to be young again has never lived, only imagined, only masqueraded. Of course, if you never eat, you keep your appetite for dinner.

The day after Jane Harrison died — an unseasonable spring day of “bitter windy rain” — Virginia Woolf recorded in her diary that she had gone for a walk in the cemetery and run into Hope, Jane’s partner, distraught and “half sleep” with grief. Virginia, who was months from publishing Orlando — her four-century love letter to Vita, the great love of her own life — recounted her encounter with the brokenhearted Hope:

We kissed by Cromwell’s daughter’s grave, where Shelley used to walk, for Jane’s death. She lay dead outside the graveyard in that back room where we saw her lately raised on her pillows, like a very old person, whom life has tossed up, & left; exalted, satisfied, exhausted.

Hope later received a note of condolence from Virginia, containing a single line. “It was more comforting than all my other letters put together,” she told a friend half a lifetime later. It read:

But remember what you have had.

Somewhere along the way, in the century of the self, we forgot each other. We forgot this vast and wonder-filled universe, of which we are each but a tiny and transient wonder.

We forgot that all creative work — be it music or mathematics, poetry or physics, anything we might call art — is a hand outstretched in the dark, reaching not for visibility but for the light that lives between us. Reaching for connection.

We forgot what Whitman knew even as he proclaimed “I celebrate myself!” — that “every atom belonging to me as good belongs to you.” No word appears in Leaves of Grass more times than you.

We are living through a pandemic of selfing — rampant self-celebration that mistakes applause for connection, likes for love. Social media companies are capitalizing on our native need for affirmation, exploiting our compromised immunity to manipulation at every turn: algorithms prioritizing selfies over sunflowers, algorithms amplifying the word I, algorithms doping us on the dopamine of being noticed, seducing us into forgetting the art and joy of noticing — that crowning glory of consciousness. And somewhere, in the quiet core of our being, this frantic hunt for likes is making us like ourselves less.

There must be another way — a way to unself just enough to remember each other, to grow a little more awake to this world that shimmers with wonder, of which any one self is only a fleck.

Whatever that way is, it is not some new technology. Maybe it is a new ethic. Maybe it is the oldest ethic.

Here is what I propose:

As an experiment, for one continuous month, make the focus of one in every three things you share on social media — wherever you normally share, however regularly or irregularly you do, however many people you reach — something other than yourself or your own work: a friend’s art project, a stranger’s poem, a record by a musician you love, the tree shimmering with majesty and mystery in the low morning light, someone in your community you admire, a bygone pioneer of something you value, a book that spun you on your axis, the lost cat sign crayoned by a neighbor’s child, the new community garden a few blocks over, news of the dazzling galaxy discovered by the dazzling new space telescope a few million lightyears over.

Try it for a month — try it on like a shirt, see how it feels. And if you don’t feel that warm glow of generosity, that good glad feeling of making another’s day, or simply the relief of a small sabbatical from the tedium of the self, then you can always go back to the old way.

Wherever you land, it will not have been a wasted month.

Without color, life would be a mistake. I mean this both existentially and evolutionarily: Color is not only our primary sensorium of beauty — that aesthetic rapture without which life would be a desert of the soul — but color is how we came to exist in the first place. Our perception of color, like our entire perceptual experience, is part of our creaturely inheritance and bounded by it — experience that differs wildly from that of other species, and even varies vastly within our own species. In that limitation lies a glorious invitation to fathom the fundaments of our humanity and step beyond ourselves into other sensoria more dazzling than our consciousness is even equipped to imagine.

That is the invitation Ed Yong — one of the most insightful science writers of our time, and one of the most soulful — extends in An Immense World: How Animal Senses Reveal the Hidden Realms Around Us (public library), appropriately titled after a verse by William Blake:

How do you know but ev’ry Bird that cuts the airy way,
Is an immense world of delight, clos’d by your senses five?

A quarter millennium of science after Blake — a quarter millennium of magnifying delight through the lens of knowledge — Yong writes:

Earth teems with sights and textures, sounds and vibrations, smells and tastes, electric and magnetic fields. But every animal can only tap into a small fraction of reality’s fullness. Each is enclosed within its own unique sensory bubble, perceiving but a tiny sliver of an immense world.

Color wheel based on the classification system of the French chemist Michel Eugène Chevreul from Les phénomènes de la physique by Amédée Guillemin, 1882. (Available as a print and as stationery cards.)

With an eye to the Umwelt — that lovely German word for the sensory bubble each creature inhabits, both limiting and defining its perceptual reality — he adds:

Our Umwelt is still limited; it just doesn’t feel that way. To us, it feels all-encompassing. It is all that we know, and so we easily mistake it for all there is to know. This is an illusion, and one that every animal shares.

[…]

Nothing can sense everything, and nothing needs to. That is why Umwelten exist at all. It is also why the act of contemplating the Umwelt of another creature is so deeply human and so utterly profound. Our senses filter in what we need. We must choose to learn about the rest.

We are insentient to myriad realities readily available to our fellow creatures — the temperature currents by which a fly, Blake’s supreme existentialist, navigates the air; the ultrasonic calls with which hummingbirds hover between science and magic; the magnetic fields by which nightingales migrate. With the perspectival felicity that science singularly confers, Yong writes:

The Umwelt concept can feel constrictive because it implies that every creature is trapped within the house of its senses. But to me, the idea is wonderfully expansive. It tells us that all is not as it seems and that everything we experience is but a filtered version of everything that we could experience. It reminds us that there is light in darkness, noise in silence, richness in nothingness. It hints at flickers of the unfamiliar in the familiar, of the extraordinary in the everyday, of magnificence in mundanity… When we pay attention to other animals, our own world expands and deepens.

No corner of the house of the senses is more fascinating — for its aesthetic gifts, its evolutionary convolutions, and its almost spiritual effects — than color.

One of Goethe’s geometric studies of color perception

“Color itself is a degree of darkness,” Goethe wrote in his poetic theory of color and emotion. Although the theory was falsified by science and revised by the very scientists whom it inspired, this particular statement from it stands as an apt description of the evolutionary history of color vision.

To see at all, ancient animals developed a type of protein receptor called opsin, which patrols the surface of the cell that contains it — a type of cell called a cone — and grabs at light-absorbing molecules, forming a partnership that sparks the chemical reaction of electrical signals that carry vital information to neurons — information which resolves in what we call vision. Some 500 million years ago, once our primordial ancestors moved from the depths to the shallows of the sea, they confronted something profound confusing from the vantage point of a creature with primitive monochromatic eyes only capable of distinguishing degrees of darkness: sunlight dancing on the surface of the rippling waves, rapidly refracting into the water. Suddenly, a single patch of visible space could vary in brightness a hundredfold from moment to moment under the flickering rays. Against this strobe assault, it became impossible to detect predator or prey.

To cope with the dangerous disorientation, our monochromat ancestors needed a way to not only detect binary variations of brightness and darkness, but to compare them. Cones and their opsins grew more and more specialized, with different types emerging to absorb different wavelengths of light — long, which we perceive as red, medium for green, and short for blue. A complex neural network emerged to compute these comparisons — neurons excited by some cones but inhibited by others, allowing creatures to detect particular colors, indistinguishable by degrees of darkness in monochromatic vision — certain shades of red and green can (and do, to the red-green colorblind) look identical in grayscale.

This process, known as opponency, is the basis of all color vision. Different animals have different types and numbers of opsins, unmooring the perception of color from its physics and making it an inherently subjective experience.

“Spectra of various light sources, solar, stellar, metallic, gaseous, electric” from Les phénomènes de la physique by Amédée Guillemin, 1882. (Available as a print and as stationery cards.)

Our own animal experience of color, as fundamental to our consciousness as it may be, came by rather haphazardly, by a glorious accident of evolution. (Then again, we could say the same of consciousness itself, and perhaps of all of life — none of it was inevitable, none part of some grand score for the symphony of chance.) Yong writes:

The first primates were almost certainly dichromats. They had two cones, short and long. They saw in blues and yellows, like dogs. But sometime between 29 and 43 million years ago, an accident occurred that permanently changed the Umwelt of one specific lineage of primates: They gained an extra copy of the gene that builds their long opsin. Such duplications often happen when cells divide and DNA is copied. They’re mistakes, but fortuitous ones, for they provide a redundant copy of a gene that evolution can tinker with without disrupting the work of the original. That’s exactly what happened with the long-opsin gene. One of the two copies stayed roughly the same, absorbing light at 560 nanometers. The other gradually shifted to a shorter wavelength of 530 nanometers, becoming what we now call the medium (green) opsin. These two genes are 98 percent identical, but the 2 percent gulf between them is also the difference between seeing only in blues and yellows and adding reds and greens to the mix. With the new medium opsins joining the earlier long and short ones, these primates had evolved trichromacy. And they passed their expanded vision to their descendants — the monkeys and apes of Africa, Asia, and Europe, a group that includes us.

This accidentally duplicated long-opsin gene suddenly expanded our rainbow by an order of magnitude:

A monochromat can make out roughly a hundred grades of gray between black and white. A dichromat adds around a hundred steps from yellow to blue, which multiplies with the grays to create tens of thousands of perceivable colors. A trichromat adds another hundred or so steps from red to green, which multiplies again with a dichromat’s set to boost the color count into the millions. Each extra opsin increases the visual palette exponentially.

It is easy, then, to imagine that if someone were to wave a magic wand over a dichromat, who sees only 1% of the colors a tetrachromat sees, and add an extra cone, the transformation would be nothing less than a revolution of reality. It would be, were our frames of reference not a stronger determinant of reality than our perceptions. (Thoreau captured this haunting aspect of the animal soul when he observed that “we hear and apprehend only what we already half know.”) When researchers took this fortuitous long-opsin gene that chance handed humans and gave it to a pair of squirrel monkeys, dichromatic by nature, the monkeys gained instant access to a world a hundred times more colorful. But instead of moving wonder-stricken through this new wonderland, gasping at every suddenly green leaf and every suddenly red berry, they went about their ordinary lives in the ordinary way, illustrating the relativity of wonder. Yong reflects:

Seeing more colors isn’t advantageous in and of itself. Colors are not inherently magical. They become magical when and if animals derive meaning from them. Some are special to us because, having inherited the ability to see them from our trichromatic ancestors, we imbued them with social significance. Conversely, there are colors that don’t matter to us at all. There are colors we cannot even see.

Art by Vivian Torrence from Chemistry Imagined by Nobel laureate Roald Hoffmann.

One hallmark of our species may be that, unlike our squirrel monkey cousins, we are animated by a restless wonderment about what lies beyond the horizon of the known and the visible. Whether we call it curiosity or imagination, it is the longing that fuels all creativity, in science or in art. And this blind spot of our vision is where the chromatic equation grows infinitely interesting.

It all began in the 1880s, when the polymathic banker turned scientist and philanthropist John Lubbock shone a beam of light through a prism, splitting it into its constituent colors and letting the rainbow fall onto some ants. Predictably, they fled from the light; unexpectedly, they ran not only for the colors he could see but from a patch just past the violet end that appeared completely dark to him. This was the discovery of the ultraviolet range of the electromagnetic spectrum — light with wavelengths between 10 to 400 nanometers, too short for the human eye to detect.

Blues from the Werner’s Nomenclature of Colours: Adapted to Zoology, Botany, Chemistry, Mineralogy, Anatomy, and the Arts, which inspired Darwin. (Available as a print and a face mask.)

This was an era when science still clung to the dangerous Cartesian binary of human exceptionalism, under which other animals experienced the world either exactly as we do or in greatly diminished ways — non-human animals were thought to either see the same rainbow we do or to be entirely colorblind. The notion that they could see color, and see it differently than we do, and see what we cannot see, was a radical demolition of dogma — too radical to fully accept. For a long while, ants were thought to be exceptional in the animal kingdom — fortunate flukes unrepresentative of the sub-human whole. Eventually, bees joined them.

But then, in a mere century of science — a blink of evolutionary time — numerous birds, fish, reptiles, and insects were reluctantly admitted into the UV-sighted ranks. Still, we excluded mammals from the realm of possibility — this is the history of our species — until, in a humbling testament to Richard Feynman’s insistence that the imagination of nature will always exceed that of the human animal, a team of scientists discovered a short cone tuned to UV light in three species of rodents. Within half a human generation, many mammals — including dogs, cats, reindeer, cows, and ferrets — were discovered to detect UV light with their short blue cones.

Now we know that most animals can perceive ultraviolet, and we are the unfortunate flukes.

Even some human animals — those who have had their lenses damaged in some way — can perceive the UV end of the spectrum as a pale blue, none more famous than Claude Monet and his water lilies, the dazzling product of his refusal to have his cataracts — a progressive clouding of the lens that filters color — surgically removed; instead, he went on painting the world as he saw it, increasingly warping the electromagnetic spectrum into otherworldly colors.

Claude Monet: The Water Lilies – Setting Sun, 1915-1926. (Musée de l’Orangerie, Paris.)

With an eye to bees — tetrachromats with opsins most tuned to blue, green, and ultraviolet — Yong winks at our human tendency toward self-reference and celebrates the supreme gift of science, that of achieving perspective:

If bees were scientists, they might marvel at the color we know as red, which they cannot see and which they might call “ultrayellow.” They might assert at first that other creatures can’t see ultrayellow, and then later wonder why so many do. They might ask if it is special. They might photograph roses through ultrayellow cameras and rhapsodize about how different they look. They might wonder whether the large bipedal animals that see this color exchange secret messages through their flushed cheeks. They might eventually realize that it is just another color, special mainly in its absence from their vision. And they might wonder what it would be like to add it to their Umwelt, bolstering their three dimensions of color with a fourth.

But bees are still trichromats, like us, just shifted along the electromagnetic spectrum. The truly mind-bending part — quite literally, for it flexes our cognitive capacity for imagination beyond the hard-wired perceptual limits of our consciousness — is when we raise color vision by another order of magnitude, to tetrachromacy: the addition of a whole other cone with a whole other opsin. Just as in the leap from dichromacy to trichromacy, a trichromat sees only 1% of the colors available to a tetrachromat. Dinosaurs were almost certainly tetrachromats, walking a psychedelic primordial world. Hummingbirds — those feathered miniature heirs of the bygone giant reptiles — are tetrachromats. They see hundreds of millions of colors and can readily distinguish between flowers that appear to us identical in hue.

One of artist Rosalind Hobley’s stunning cyanotype portraits of flowers, which rely on a chemical process sensitive to light on the edge of blue and ultraviolet

But for a trichromat to imagine tetrachromacy is as challenging as for a two-dimensional creature to imagine a three-dimensional world — we inhabit a chromatic Flatland, in which the vision of a hummingbird remains to us as enticing and elusive an abstraction as a Klein bottle.

Yong writes:

[Hummingbirds] don’t just have human vision plus ultraviolet, or bee vision plus red. Tetrachromacy doesn’t just widen the visible spectrum at its margins. It unlocks an entirely new dimension of colors.

[…]

Picture trichromatic human vision as a triangle, with the three corners representing our red, green, and blue cones. Every color we can see is a mix of those three, and can be plotted as a point within that triangular space. By comparison, a bird’s color vision is a pyramid, with four corners representing each of its four cones. Our entire color space is just one face of that pyramid, whose spacious interior represents colors inaccessible to most of us.

Rucker’s Hermit Hummingbird by John Gould, 1861. (Available as a print and as stationery cards, benefitting the Nature Conservancy.)

In a wonderfully Dr. Seussian passage, Yong sums up the revolutionary discoveries of violinist turned sensory ecologist and evolutionary biologist Mary Caswell “Cassie” Stoddard, who spearheaded the hummingbird research:

If our red and blue cones are stimulated together, we see purple — a color that doesn’t exist in the rainbow and that can’t be represented by a single wavelength of light. These kinds of cocktail colors are called non-spectral. Hummingbirds, with their four cones, can see a lot more of them, including UV-red, UV-green, UV-yellow (which is red + green + UV), and probably UV-purple (which is red + blue + UV). At my wife’s suggestion, and to Stoddard’s delight, I’m going to call these rurple, grurple, yurple, and ultrapurple. Stoddard found that these non-spectral colors and their various shades account for roughly a third of those found on plants and feathers. To a bird, meadows and forests pulse with grurples and yurples. To a broad-tailed hummingbird, the bright magenta feathers of the male’s bib are actually ultrapurple.

[…]

As a violinist, [Stoddard] knows that two simultaneously played notes can either sound separate or merge into completely new tones. By analogy, do hummingbirds perceive rurple as a blend of red and UV, or as a sublime new color in its own right? When they make choices about which flowers to visit, “do they group rurple with reds, or do they see it as an entirely different hue?” she asks. They can tell that it’s different from pure red, “but I can’t articulate what it looks like to them.”

Goethe’s color wheel, 1809. (Available as a print.)

Many more ineffable wonders of perception come abloom on the pages of Yong’s An Immense World. Complement this fragment of it with the great nature writer Ellen Meloy on the conscience of color from chemistry to culture and physicist Arthur Zajonc on the entwined history of vision and consciousness, then revisit cognitive scientist Alexandra Horowitz on how to see reality beyond the habitual limits of our perception.

The Universe in Verse: A Poetic Animated Celebration of Science and the Wonder of Reality

Uncommon Presents from the Past: Gifts for the Science-Lover and Nature-Ecstatic in Your Life, Benefitting the Nature Conservancy