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Taking some inspiration from the finding that a small proportion is able to perceive significantly more colors than the rest of the population, I would like to explore to what degree similar traits can be attained via natural selection. A short segment on 'tetrachromatic' eyes.

It may be the case that human's learned behavior, like digital tool-making/hardware will complicate the arithmetic. So perhaps we can begin the evolutionary experiment millions of years earlier when hominids had relatively basic tools.

Purely for benchmarking purposes, the mantis shrimp has among the most 'vivid' color perception, which has hexakaidecachromatic vision, if you will humor my neologism.

enter image description here

In hindsight, it's plain to see that the hominid-to-human arc culminated favorably; we became a prominent fixture of the earth's biome without the need for ultra-sensitive, bells-and-whistles vision. This will mean that the onus will be to introduce environmental factors that will require very advanced color sensitive adaptations from humans.

Question

What environmental factors need to be present on a world such that our early ancestors would evolve extremely color-sensitive vision adaptations?

Further clarification:

  • If necessary, explain physiological assumptions. Let's keep this as open-architecture as possible though: i don't want to undermine answerers creativity.
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  • $\begingroup$ The shrimp's vision might be called "deca(h)exichromatic" instead, please check at your side. And what were the evolutionary threats to them that helped them evolve this kind of vision? $\endgroup$
    – Vesper
    Jun 1, 2023 at 8:52
  • $\begingroup$ Also I have read that those shrimps have separated from the rest of class as far as "not long after the Cambrian" which is some serious 600MYA, probably your plan of adapting humanity's eyes should start with early mammals or even earlier? $\endgroup$
    – Vesper
    Jun 1, 2023 at 8:58
  • $\begingroup$ Reading the wiki article on mantis shrimp it seems they can't actually see much more than humans but it is rather a tradeoff where mantis shrimp have complex eyes and simple brains whereas humans have simple eyes and complex brains. As you want your humans to be intelligent, getting evolution to pick complex eyes seems difficult. $\endgroup$
    – quarague
    Jun 1, 2023 at 9:02
  • $\begingroup$ @Vesper My reading has that question unanswered. It's a big mystery why that shrimp needs to see a trillion colors. But many insects are tetrachromatic, a bit more than humans, which helps them see mates while still hiding from predators, or differentiate flowers. $\endgroup$
    – user458
    Jun 5, 2023 at 15:14
  • $\begingroup$ For the OP, the chromancy of all organisms is in reference to its color definition, not the broadness of the spectrum it sees. In the way, a colorblind man sees the same spectrum but fewer colors. So those are two questions, seeing more spectrum or seeing the same spectrum with more colors. $\endgroup$
    – user458
    Jun 5, 2023 at 15:18

2 Answers 2

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You need only look at Plants and the evolution of insects in our very own garden.

Plants evolved flowers almost 130 million years ago, long after sexual reproduction through spores and pollen. Insects, however, had been on the earth for well over 300 million years.

So Plants needed a way for certain (not all) insects to exclusively come to its flowers, and spread its pollen. How to do this? Flowers developed markings attuned to only certain insects in certain UV ranges - this way bees, butterflies and other insects know exactly which flowers have the nectar they need. If you collect flowers in your garden and place these under a UV light, you will see these markings that normal animals (and some insects) cannot see.

Insects 'co-evolved' along with the flowering plants as also they have an advantage to perceive discreet UV light ranges to give them an evolutionary advantage (an additional food source) and reproduce more. Plants 'co-evolve' further, and this relationship continues until the distinction is so great new species arise with new light-frequency detection and production.

enter image description here

Original article : https://en.wikipedia.org/wiki/UV_coloration_in_flowers

Transferring this mechanism to humans using an established precedent then is easy - perhaps plants produce fruit that are advantageous only if humans eat them to give an advantage over other species of plant. Those humans that have extra UV perception can take advantage of this new food source, and reproduce themselves more often, co-evolving with the fruiting plant, eventually expanding the range of their perception in this direction.

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  • $\begingroup$ Well, that fruit should be a mono diet for human ancestors to evolve extra color perception. Humans are omnivores, we can eat a multitude of fruit types, as well as some prey and actually some predators if we best em, so selection by a single type of fruit looks impossible, unless that fruit does more than just satiate. Say its consumption coincides with greater/possible fertility, extra capabilities (mmm, m-magic) etc, but it's not only elusive, camouflaged etc, but also ever-changing including its UV marks, and needs to be collected at exact time for example to work properly. $\endgroup$
    – Vesper
    Jun 5, 2023 at 16:45
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Camouflage

Had Mother Nature evolved both predators (critters that eat humans) and prey (critters that humans eat) with better camouflage, our eyes would have developed better methods for detecting both.

Keep in mind that the nature of speculating about evolution is that if X happened then Y might have happened. There's no way to definitively prove the causal relationship between speculated X and Y. That might not be possible even with known evolutionary changes (Y happened and X existed so we can assume a causal relationship between X and Y). So when you say , you really mean , right?

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  • $\begingroup$ Interesting angle! I personally think it fits the science-based tool-tip, but I'm not too picky about that. Evolutionary narratives for special traits have been slotted to that tag by me a good bit in my older posts. $\endgroup$ Jun 1, 2023 at 7:43
  • $\begingroup$ I think spotting camouflage is probably the answer. There is not a lot you can see with 16 channels the you can't see with three, as most reflection colours are fairly broad band. But it gets a lot harder to match colours. $\endgroup$ Jun 1, 2023 at 8:12
  • $\begingroup$ AFAIR human ancestors developed red because of tigers, which otherwise have a decent camo vs green/blue eyesight of their prey. Then they required more red because of emerging social relations, detecting "greener red" helped somehow (maybe seeing who's sick?). Probably better night vision could be required in pre-fire era to detect some extra threats that would otherwise eliminate tribes, and that could evolve into better blue or green, but getting specialized purple would probably require more evolutionary pressure than just camouflage. $\endgroup$
    – Vesper
    Jun 1, 2023 at 8:49

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