Around 540 million years ago, the ancestors of most modern animal groups suddenly appeared on the scene, in an outburst of speciation known as the Cambrian explosion. Many of these pioneering creatures left fossils behind. Some are so well preserved that scientists have been able to use scanning electron microscope images to piece together their inner anatomy, eyes included, and reconstruct their owners’ view of the world. ... But these eyes were already complex, and there are no traces of their simpler precursors. The fossil record tells us nothing about how sightless animals first came to see the world. This mystery flustered Charles Darwin. “To suppose that the eye, with all its inimitable contrivances ... could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree,” he wrote in Origin of Species. ... in the very next sentence, Darwin solves his own dilemma: “Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist … then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real.” ... The gradations he spoke of can be shown to exist. Living animals illustrate every possible intermediate between the primitive light-sensitive patches on an earthworm and the supersharp camera eyes of eagles. ... Even under the most pessimistic conditions, with the eye improving by just 0.005 percent each generation, it takes just 364,000 years for the simple sheet to become a fully functioning camera-like organ. As far as evolution goes, that’s a blink of an eye. ... But simple eyes should not be seen as just stepping-stones along a path toward greater complexity. Those that exist today are tailored to the needs of their users. ... Nothing that sees does so without proteins called opsins—the molecular basis of all eyes. Opsins work by embracing a chromophore, a molecule that can absorb the energy of an incoming photon. The energy rapidly snaps the chromophore into a different shape, forcing its opsin partner to likewise contort. This transformation sets off a series of chemical reactions that ends with an electrical signal.
Avian vision works spectacularly well (enabling eagles, for instance, to spot mice from a mile high), and his lab studies the evolutionary adaptations that make this so. Many of these attributes are believed to have been passed down to birds from a lizardlike creature that, 300 million years ago, gave rise to both dinosaurs and proto-mammals. While birds’ ancestors, the dinos, ruled the planetary roost, our mammalian kin scurried around in the dark, fearfully nocturnal and gradually losing color discrimination. Mammals’ cone types dropped to two — a nadir from which we are still clambering back. About 30 million years ago, one of our primate ancestors’ cones split into two — red- and green-detecting — which, together with the existing blue-detecting cone, give us trichromatic vision. But our cones, particularly the newer red and green ones, have a clumpy, scattershot distribution and sample light unevenly. ... Bird eyes have had eons longer to optimize. Along with their higher cone count, they achieve a far more regular spacing of the cells. But why, Corbo and colleagues wondered, had evolution not opted for the perfect regularity of a grid or “lattice” distribution of cones? The strange, uncategorizable pattern they observed in the retinas was, in all likelihood, optimizing some unknown set of constraints. What these were, what the pattern was, and how the avian visual system achieved it remained unclear. ... Determining whether a system is hyperuniform requires algorithms that work rather like a game of ring toss. ... Hyperuniformity is clearly a state to which diverse systems converge, but the explanation for its universality is a work in progress.
Blue is a rarity among plants and animals. When it does occur in nature, it often isn’t truly blue, but rather a trick of diffraction, or the scattering of light, which is the case for bird feathers, sky, ice, water and iridescent butterfly wings. ... In response to growing pressure from consumers across the globe, Mars announced in February that over the next five years it would remove artificial colors from all the processed foods it makes for human consumption, and that pigments found in natural substances would take their place. ... In 2013, the Food and Drug Administration approved Mars’s petition to use the microscopic algae spirulina to make the first natural blue dye approved for use in the United States. As a result, any food manufacturer in the country can legally use spirulina as a colorant. Mars spent years researching spirulina’s safety; in order to overhaul 1,700 or so recipes and update its global manufacturing capabilities, the company desperately needs a substitute for synthetic Blue No. 1, as does the rest of the industry. But right now, there isn’t nearly enough spirulina dye to go around — and in any case, sometimes it doesn’t yield just the right blue, or the color degrades and comes out blotchy, or it tastes odd. ... Humans are color-seeking animals, and food companies learned to manipulate that trait early. ... One Mars executive told me that to convert only its blue M&Ms to spirulina blue, the company would, in his estimation, need twice the current global supply. ... last year the global market in natural colors was worth an estimated $970 million, up 60 percent since 2011. Natural colors now represent more than half the food-colors market in dollar terms.
The capital of the Kunene region, Opuwo lies in the heartland of the Himba people, a semi-nomadic people who spend their days herding cattle. Long after many of the world’s other indigenous populations had begun to migrate to cities, the Himba had mostly avoided contact with modern culture, quietly continuing their traditional life. But that is slowly changing, with younger generations feeling the draw of Opuwo, where they will encounter cars, brick buildings, and writing for the first time. ... How does the human mind cope with all those novelties and new sensations? By studying people like the Himba, at the start of their journey into modernity, scientists are now hoping to understand the ways that modern life may have altered all of our minds. ... Like an irregular lens, our modern, urban brains distort the images hitting our retina, magnifying some parts of the scene and shrinking others.