RENEE MONTAGNE, HOST:
Let's talk now about color in nature, as part of our series on color - think the orange stripes of tigers, iridescent-blue butterflies, green snakes. As NPR's Rae Ellen Bichell reports, it's taken hundreds of millions of years of evolution to produce this technicolor paint box.
RAE ELLEN BICHELL, BYLINE: Let's zoom back to about 600 million years ago. The sun is shining. The Earth is made of stuff that absorbs and reflects light.
(SOUNDBITE OF OCEAN WAVES)
BICHELL: But for the slimy blobs of life that have started to take shape, the color of the sky or the sea or even their fellow sponges and worms doesn't matter a single bit because they don't have eyes.
ANDREW PARKER: Before the eye evolved, you just wouldn't have seen what was there.
BICHELL: Andrew Parker is a biologist at the Natural History Museum in London. He studies the evolution of color. He says creatures back then just floated around. They were aware of sunlight, but they didn't have any of the biological bits and pieces you need to perceive color.
PARKER: It's like it doesn't exist.
BICHELL: They lived in a world of light and dark - movement and stillness. Then, as Parker tells it, about 550 million years ago, something really big happened.
PARKER: A predator that could swim quickly evolved vision.
BICHELL: That predator looked something like a big shrimp, and now it had eyeballs. Those first eyes were game changers.
PARKER: Once eyes evolved, then that's when color really kicked off.
BICHELL: Think about it, Parker says. If you're a juicy slime blob that just happens to be yellow or red, before eyes it didn't matter what color you were, but now...
PARKER: It'll just act as a beacon to attract predators to it.
BICHELL: And the slime blob is lunch. So the species would've had to adapt. Color becomes the way to keep yourself fit, well-fed and sexy enough to get the cool guy or girl - or shrimp-thing. Now, millions of species and a few mass extinctions later, fins, fur and feathers have come up with ways to make every color in the Pantone chart. Take pink flamingos, for example. Baby flamingos are knobby-kneed, fluffy and awkward. They are also light gray. To make themselves pink, they have to steal pigments from other animals or plants by eating them. Sarah Hallager is the curator of birds at the National Zoo.
SARAH HALLAGER: Flamingos around the world - everything they eat, everything that makes them pink is carotenoids.
BICHELL: Carotenoids are natural pigments that make carrots orange and beets red. They're really abundant in nature. Lots of animals get their color from eating them. Flamingos get carotenoids mostly from shrimp and crabs. Robins and cardinals get them from berries. Koi fish turn orange from munching on algae. It even works for humans sort of.
HALLAGER: If you eat way too many carrots and the whites of your eyes turn a little pink hue, that's the same process.
BICHELL: Eat pink, become pink. Eat red, become red - seems simple. The thing is...
HALLAGER: You can't feed flamingos blueberries and turn them blue. They're only programmed to respond to carotenoids, which produce the pink plumage.
BICHELL: Turns out animals have a lot of color limitations like that. Pink and red are easy. But other colors aren't. Rick Prum, who studies birds at Yale, says blue is an especially difficult color to make.
RICK PRUM: Blue is fascinating because the vast majority of animals are incapable of making it with pigments.
BICHELL: The most brilliantly blue things, like a peacock feather or even a human blue eye, don't have a single bit of blue pigment in them. So how come they're so blue?
PRUM: They have evolved a new kind of optical technology, if you will, to create this color.
BICHELL: Blue morpho butterflies are a great example.
DAN BABBITT: Oh, this is - a huge group of morphos just flew by.
BICHELL: Dan Babbitt keeps some at the Smithsonian Museum of Natural History.
BABBITT: This is a giant butterfly. It's about six-inch wingspan, and they are bright, iridescent blue.
BICHELL: Blue morphos have tiny, transparent structures on the surface of their wings that bounce light in just the right way to make them appear a vibrant blue - so bright it hurts your eyes. Antonia Monteiro studies butterfly wings in Singapore. She says, a lot of animals use different materials to get the same effect.
ANTONIA MONTEIRO: Everywhere you look, organisms have been inventing different solutions to the same color.
BICHELL: She says butterflies do it with chitin, which is the same stuff that makes crab shells tough. And birds use keratin, which is what our fingernails are made of, with little bubbles in it to reflect light in just the right way. And it turns out that having optical structures to make blue also solves a different color challenge - going green.
PARKER: Green is a pigment that animals really have had a problem making.
BICHELL: And that's unfortunate, says Andrew Parker, if you want to lurk on a green, leafy planet. So some land animals dabble in a little color mixing.
PARKER: All the green snakes and green frogs, they're actually not green at all. They've evolved a yellow pigment and a blue structural color, and the two combined produce a green effect.
BICHELL: And all this was long before the first painter ever picked up a brush. Rae Ellen Bichell, NPR News.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.