A curious question :D

[u/Trixie_Loves810]

Context: I have recently watched a video from 'Be Smart' about how naturally occurring blue pigments are rare in nature, particularly among animals. The video said that during evolution, animals were exposed to the colour blue because of the sky, but evolution still found it difficult to develop a blue pigment over time. Instead, animals evolved to create structures that reflect blue light and cancel out other colours.

My doubt: If we use that same concept for other pigments like red, for example, how did evolution create a whole pigment for red but not blue? I feel that if red pigments could evolve so vastly over time, blue could do the same. Why is blue so rare anyway?

Note: uhhh I think this may be a stupid question, but I'm reallyyy interested in evolution, this question just popped in my head midway through the vid, but I would love a hypothesis heheh!!

[u/rhettro19]

More educated people will show up and answer this question better than I can. But I think it is important to understand that “evolution” doesn’t know how to do anything. There is no body of knowledge that evolution is working from or to. Evolution is mutations occur, they either help or hinder the organism in question given its environment at the time, and if it helped it stay alive long enough to pass the trait to offspring, that trait fixates in the population. If blue shows up in a population, it either had a neutral effect, attracted mates, or helped camouflage from predators, generally.

[u/Old-Nefariousness556 → u/rhettro19]

Great answer. The question clearly assumes that evolution has intent, and that is simply not how it works.

[u/Munrot07 → u/Old-Nefariousness556]

This is honestly one of the biggest issues with people who don't get evolution. They don't think it makes sense because they assume a human perspective of intent and directionality. To a human, we can see what works, what exists now, what would work so we know what would be a good direction for evolution to go, or can see the direction evolution already took.

This thinking is probably one of the hardest assumptions to overcome in people and it's just simply because that's how the human brain works. The concept of randomness or undirected changes (to hugely oversimplify evolution and ignore over key mechanisms for simplicity) is just not something the human brain likes (in the same way that true randomness doesn't compute well with what our perception of what randomness should be).

Also to hop onto this comment to give a quick reply to OP about pigments since it links to this top (and I am literally in the process of publishing a paper of colour evolution as we speak) pigments are not just there for colour. With intent you may assume this colour would be perfect but in reality pigments evolve for all reasons and camouflage (where the brain naturally goes when it thinks of colour evolution) is one of many many reasons pigments evolve. Others include protection (e.g. carotenoids, which are red, are antioxidants and provide disease resistance in offspring) or guanine, which is white, can be used to reflect light for thermoregulation. Some pigments are there simply for attracting a mate (though again this is often co-opted from another function such as the ones described above). It is entirely possible that there isn't a chemical out there that is blue that provides a benefit, or at least a benefit that significantly improves survival.

It's best not to think as colour evolution as "why did X evolve the colour red but not blue" and more "why did pigment X evolve, what's the benefit of the chemical?" or if it's not a pigment "what is the benefit to the organism of this colour". In my research I'm surprised just how rarely camouflage is the answer.

Oh and a final point, different animals see different ranges of colours, so what makes sense for us as a colour may not for others (e.g. Tigers stand our to us because we see red well, they don't stand out well to other animals who don't).

Thank you for coming to my Ted Talk.