The natural world is full of  beautiful, vibrant colors.

From birds of paradise to... the  other kind of birds of paradise. And as well as being stunning, a lot of  these colors evolved to serve a purpose.

Like how the neon colors on  a poison dart frog scream, “If you eat me you’ll be sorry!”. Or how a male bird’s plumage  entices mates to come hither. But this brings up an interesting question: if no animal had eyes capable  of perceiving all those colors, why would colorfulness evolve in the first place?

And if no life was super colorful,  why would we evolve color perception? Is this the next big chicken-or-egg question? Well, one pair of scientists  has already had a go at figuring out which came first:  colorfulness or color vision. [♪ INTRO] There’s no one way to be colorful.

Bright, iridescent, color changing… you  name it, the natural world probably has it! What you, or a bumblebee,  or SciShow’s unofficial dog Perry see as color depends on a couple things. First, there’s the actual production of the color.

Some color comes from  pigments, molecules that absorb certain wavelengths of  light, and reflect the rest. This is, for example, how adult  flamingos get their pinky-coral color: pigments called carotenoids in the shells of yummy yummy shrimp wind up  settling in their feathers. But color can also have a structural origin.

Sometimes, a material has such a  weird shape on a microscopic level that sunlight reflects off in  a way that produces a new hue. This is how a bunch of life  produces vivid shades of blue, from the scales on a Blue Morpho butterfly wing, to the carefully arranged collagen  fibers inside a mandrill’s snout. Meanwhile, some animals combine pigments and structural color to get unbelievably  rich greens, reds, and turquoises.

But all that light bouncing around also has  to be perceived for it to count as color. And how animals see color  comes down to their physiology. Take honeybees, for example.

They can’t see what we define as the color red, but they can see shades of blue,  green, and even ultraviolet, thanks to the type of photoreceptors  they have in their eyes. Color perception also depends on  the type of light-sensitive proteins inside those receptor cells,  which scientists call opsins. And finally, the last piece  of the puzzle is the brain, and how it decodes all those incoming signals.

So combine light, receptors, opsins, and a brain, and you’ve got a magical world of color. But why does color exist? Or rather, the rainbow of colors you  find in living things around the world?

In a word: signalling. The male Wilson’s bird of paradise has  vibrant patches of red, blue, and yellow, as well as iridescent tail feathers, which  can be seen easily on the dim forest floor. Those flashes tell the much  duller by comparison females, “I’m here, I’m healthy, and I’m awesome”.

On the flipside, some species of  octopus can change their color in order to blend in almost  seamlessly to their surroundings. And so on, and so forth. We can only provide so many  examples in a 2100-word script.

I’m sorry I have not brought up  your favorite colorful animal. They all are cool and have good reasons. But color and color vision  must have gotten here somehow.

So what evolutionary forces  got us to where we are today? Well in a paper published in 2024, two  evolutionary biologists tried to find out. More specifically, they wanted to figure  out how and why conspicuous colors exist: vibrant colors that help organisms stand out, as opposed to the greens, browns,  and greys that help them blend in.

They started out with five hypotheses  for what came first and why: One, that it evolved in fruit  first to attract animals to eat them and spread the seeds inside. Two, that it evolved in flowers  first to attract pollinators. Three, that it evolved as a warning.

And four, that it evolved to attract a mate. The fifth hypothesis was that color  vision evolved before any and all of that. To test these hypotheses, they  reviewed and combined the results of previous studies in order to construct their  own evolutionary, or phylogenetic trees, and then tracked the history  of all these functions.

Where possible, the research duo  backed up these reconstructed trees with evidence from the fossil record. Then, they lined up all those reconstructions to compare them all on the same timeline. They were especially looking to reconstruct what the evolutionary order of events looked like.

That would tell them which trait is the oldest. However, this was not a perfect approach. Evolutionary tree reconstructions  have their limits.

The further back in time you’re trying  to go, the more uncertain your model. And evolution doesn't just tick steadily along. Sometimes, traits spring up really quickly,  only to disappear just as quickly again.

Or you might have a similar-looking trait  showing up in multiple species all at once. That makes it hard to definitively say that “the common ancestor of both  organisms X and Y had trait Z”. Plus with color, you have  the added complexity that it doesn’t stick around well in fossils.

So it’s tricky to bolster a  speculative tree with hard evidence. But despite those shortcomings,  evolutionary trees are still one of the best approaches we  have for understanding our past. But before we can get to  the research team’s results, we’ve got to keep the lights on with an ad.

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It’s fun for the whole family! Ok, so remember when I  mentioned the bird of paradise with its dazzling colors to attract a mate? Well it turns out, that whole  shtick is a relatively recent thing.

According to two surveys this 2024 paper reviewed, creatures attracting mates with flashy hues only showed up around 100 million years ago. That’s solidly in dinosaur  territory, timeline-wise. So it might not sound “recent”  until you realize life of any kind may have existed as  far back as 4 billion years ago.

After reconstructing different  potential versions of family trees, the researchers found that color  for mating evolved mostly in two key animal groups: arthropods and chordates. Better known as the group containing  spiders, insects, and centipedes… and the group containing  everything with a spinal cord. To find how far back this kind of coloration went, the research duo looked for  cases where the males and females were sexually dimorphic, meaning  there were obvious visual differences.

And during their hunt through  the evolutionary trees, they identified some fish from  around 97 million years ago where the colors were probably different. But when they dug through the fossil  evidence, they did find one outlier: A feathered dinosaur which lived around  160 million years ago, called Anchiornis. The fossil was preserved with a  tuft of red plumage on its head, and paleontologists think that these red  feathers were used in mating displays.

It’s a case that highlights how  color can pop up at any time, only to disappear with a species’ extinction,  leaving no trace in today’s animals. But let’s move on to our  next kind of colorfulness: If the most recent development of  color was for getting other animals to come hither, then the second most recent  was for, well, kind of the opposite. Coloration as a warning sign,  also known as aposematism, may have evolved around 130 million years ago.

Based on previous phylogenetic studies, the authors of this 2024 report think  it probably evolved in insects first, and maybe in the ancestor of  particular butterflies and moths. But that would only put the start  date at around 105 million years ago. Meanwhile, looking at the fossil evidence, they identified an ancient Lebanese  cockroach preserved in amber that had distinctive warning colouration.

It’s 130 million years old. Now, their paper did point  out one study from 1998 which suggests some Cambrian fossils were  iridescent as a way of warning. For those of us who don’t have  the geologic timeline memorized, the Cambrian was around 500 million years ago!

But even if you count iridescence  as a type of colorfulness… which these researchers really don’t… the link between color and aposematism in  this case is, quote, “highly speculative”. So let’s take another step back in  time and we see that color starts showing up in flowers: somewhere  around 200 million years ago. That’s when the oldest  angiosperms, or flowering plants, start to lure pollinators with vivid hues.

And some of those pollinators got turned  into fossils with little bits of pollen still stuck to them, backing up the  estimates based on evolutionary trees. But insect pollinators like beetles  and flies were already buzzing around before this point in the timeline,  and were instead drawn to an older group of plants called gymnosperms. Instead of seeking out colorful bouquets, these insects were going for  appetizing-looking “fruits”.

Gymnosperms don’t develop real  fruits like angiosperms do, but they can have seeds covered  in bright, fruit-like flesh. Such red, yellow and orange feasts date  back to the late Carboniferous period, between 307 and 299 million years ago. Meanwhile, some of the most  ancient groups of flowering plants, including the group that  now contains water lilies, and the group that contains star  anise, had fleshy fruits too.

There’s some debate about  how old those ancestors are, but most of the studies and fossil  evidence the authors reviewed put them in the range of 200  to 250 million years ago. So of all the stuff this research duo looked at, that makes fruits the oldest conspicuously  colorful thing with a purpose out there. But when did life develop the  ability to see any of this?

It turns out, way earlier. Like hundreds of millions of years earlier. According to the authors’ research, color vision may have been  around 550 million years ago.

But reaching that conclusion wasn’t as  easy as it was for the other hypotheses. After all, you can look at a plant or  animal today and see that it’s colorful, but how do you know which  animals have color vision, let alone what it actually looks like for them? Think back to when we were talking  about photoreceptors and opsins.

It’s probably a good idea to start  by checking if the thing has those. But not all opsins are involved  with vision, so that’s not enough. In currently living species,  scientists can also use behavioural tests like the grey card method.

Basically, animals are trained to associate  a certain color with a food reward. Then, they’re shown a set of grey cards  and one color card, and asked to choose. If the animal still picks the colored card, then that should mean they’re  able to see that color.

To find the origins of color vision,  the research duo started with a fairly comprehensive review  of modern animals from 2003, which concluded that lots of  arthropods have color vision, as do many a chordate…from ray-finned  fishes, to birds, to yes, mammals like you. The researchers then looked at  the evolution of all those groups, and proposed the first case of color vision  likely evolved in an arthropod ancestor, which lived around 550 to 500 million years ago. But why would it need that color vision?

Or the first chordate to evolve their own version? Why did life manage to evolve color vision before the colors they might  want to see with that vision? Well, first of all, it’s not like the Earth  was in greyscale for billions of years.

Water is naturally blue. The sky was a shade of orange for a while. Rocks have minerals that come  in a full rainbow of colors.

Plants are green because of the  chlorophyll they use for photosynthesis. And so forth. So maybe, color vision just made  it easier to recognize objects, and better navigate the world.

In fact, in a paper published back in 2000, one scientist suggested that color vision  might have made it easier, in general, for ancient marine animals  to see in shallow waters. In that particular environment, beams  of sunlight will travel through ripples on the water’s surface and  create continuously flickering, high contrast patterns on everything  they bounce off of in the water. And if everything is always looking a little  bit different to your primitive eyeballs, that kinda makes it hard to avoid the  predator that’s trying to eat you.

So color vision may have helped  to dull down this contrast, and smooth out what an animal could see. In other words, it may not have  evolved for life to see color at all! Ultimately, the science behind all  these hypotheses is a little imperfect.

And until someone invents a proper time machine, we may never know the exact  evolutionary play-by-play. But for now, the question of “which  came first” for color and color vision really does seem to be a chicken and egg problem… because the first egg got laid  way before chickens existed, even if you only count the ones with shells. I guess the real question is,  what color was that eggshell, and was there anyone around who could tell? [♪ OUTRO]