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I've got a humanoid race living in a extremely bright and hot desert. Would there be a plausible or realistic reason for them to develop without eyesight, due to the harsh rays of their sun? Or, instead of eyes, developing some other form of vision (echolocation, some sort of extra sense, etc)?

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  • $\begingroup$ anything is possible.... $\endgroup$ – άλεξ μιζέρια Jul 4 '16 at 19:24
  • $\begingroup$ Most blind species occur were no light is present at all, like at the bottom of oceans. Not in a desert where the sun bakes the land. $\endgroup$ – cybernard Jul 5 '16 at 4:23
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    $\begingroup$ You are going to have to provide a reason why they don't become nocturnal. The quickest way to avoid the sun is to only come out at night. Plenty desert creatures do this. $\endgroup$ – DrBob Jul 5 '16 at 11:03
  • $\begingroup$ I would say it is more likely they evolved with eyes capable of handling the harsher sun, but it is your world. $\endgroup$ – Marshall Tigerus Jul 5 '16 at 14:38
  • $\begingroup$ dont we have animals that live in bright and hot deserts on earth that have eyes. Maybe instead we get a second eyelid, kind of like some aquatic animals (crocodiles come to mind), one that is clear but works like sunglassess, so we can see well and safely in bright light and windy sandy areas, but can lift them up for the dark nights. $\endgroup$ – Ryan Jul 6 '16 at 16:48
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Vision has a lot of advantages as a sense. It's very long-ranged, and provides a lot of information. Eyes evolved several times in Earth's history, and take lots of different forms. Human eyes are much like those of other primates, which are similar to those of other mammals.

It seems likely that if life evolved naturally in your setting, some kind of vision would exist, although it might be very different from ours.

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    $\begingroup$ The ability to image surroundings occurred very early in Earth's evolution, and as you said, it occurred often. The only place that blind creatures evolve seems to be in caves. Even deep ocean life evolves some kind of vision because organisms also evolve luminescence. $\endgroup$ – Howard Miller Jul 5 '16 at 4:03
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No. Vision is by far the most important sense for a humanoid species. It would, perhaps, be plausible for a non-humanoid race to evolve a stronger reliance on other senses to survive in the desert.

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  • $\begingroup$ for humans* not humanoids , an humanoid could be anything that looks like a person. $\endgroup$ – άλεξ μιζέρια Jul 4 '16 at 19:23
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    $\begingroup$ A humanoid race, by neccessity, has a lot of the features humans do. Unless their existence is nonsensical no humanoid race would evolve in the described desert. Even if it started as a semi-humanoid race it would evolve into something different, not a humanoid. $\endgroup$ – Annonymus Jul 4 '16 at 19:34
  • $\begingroup$ Just to clear things up; humanoid, by my definition at least, would include anything that is superficially human-like in structure, not necessarily function. Grey aliens, for example, are humanoid, yet in most media have a completely different internal structure and completely different functionality. $\endgroup$ – autumnstorm451 Jul 4 '16 at 19:45
  • $\begingroup$ Grey aliens are also impossible. It makes no sense from an evolutionary perspective for something to evolve in a humanoid shape under these conditions. $\endgroup$ – Annonymus Jul 5 '16 at 6:03
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Check out other desert animals - they also have eyesight!

In general, eyesight itself is quite vital, so you may not expect for it completely missing, especially taking into account that albedo is not so extreme in the brown-yellow sand. (unlike the poles, where everything's white, so "snowblind" state is a general phenomena)

Reduced eyesight is perfectly possible, though I'd separate it more - our eyes are able to detect colors and light with two different types of cells(?), and having less of the latter sounds realistic for me.

I'm not an expert, so I'm not sure, how would that change the ability to see, so it may or may not be a better eyesight with less light receptors, but it's a topic for another (likely rather biology-related) question.

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I would be of the opinion that for land animals to have not have evolved eyes, the habitable land area on your planet must consist solely of this desert. If they live in an extremely bright and hot desert, would it make more sense for these creatures to be nocturnal? Or perhaps if it is too cold at night (as with Earth deserts), they are active during twilight hours. If so, eyes would most likely have evolved.

With that in mind, what is the evolutionary advantage pushing these creatures to be active during the day, and thus having no use for eyes? Are they protected from nocturnal predators when sleeping? Just something to consider.

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  • $\begingroup$ That's a good reason to not go nocturnal, predators! Or... A lack of prey! $\endgroup$ – Aarthew III Jul 5 '16 at 22:35
  • $\begingroup$ But then you would need to reason why no prey/predators to this species evolved to be nocturnal. Evolution will typically fill every niche. $\endgroup$ – Andrew Recard Jul 6 '16 at 2:31
  • $\begingroup$ @Matthew Stone ? Either way humans would not go nocturnal. Whether or not there are dangerous predators or no prey at night the end result would remain the same. Humans become diurnal. $\endgroup$ – Aarthew III Jul 6 '16 at 3:05
  • $\begingroup$ Our evolutionary ancestors were once nocturnal. When dinosaurs roamed around during the day, they were able to sleep in their burrows where they were safe. If a group of humans were placed on a hostile planet that was safe during the night, we would quickly adjust to a nocturnal lifestyle (with a method of hiding), then assuming millions of years of natural selection our eyes would likely see better in the dark, along with any other changes that may occur. $\endgroup$ – Andrew Recard Jul 6 '16 at 3:13
  • $\begingroup$ @Matthew Stone My point was that if there were predators (say dinosaurs) that roamed at night or a lack of active food humans would stay diurnal. This in turn would lead to their need to replace eyes with something more suitable in the bright sun. $\endgroup$ – Aarthew III Jul 6 '16 at 4:00
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If your humanoids are nocturnal and live on a moonless planet orbiting a star on the galactic rim then they’ll be living in a nearly pitch black environment, in which case lacking eyesight makes perfect sense.

Maybe daylight is too hot to survive or the planet's magnetosphere is too weak to adequately protect them from ionizing particles?

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Maybe you could go with them evolving underground(Due to extreme temperatures or something similar). Then as time went on they developed an ability(Technology? depends on setting and their tech level) to go to the surface. As primarily underground creatures, they probably would not evolve eyesight (Or even loose it if they had it at some point). If days are to hot to be outside, and nights extremely dark, there would be no need for eyesight to evolve.

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i think it still depend on your race and its evolution. if your entire world is desert like this, then it possible for your species to skip the evolution of eye completely (thus avoid mirage), to develop echolocation or sense of smell, hearing, or heat (like the rattlesnake).

however, if your race came from somewhere else, or had evolved eyes already, then it s more plausible for them to add some features like an outer layer which act like sunglass, or switch their activity to nocturnal or crepuscular (at twilight) instead of devolve your eyes then evolve something else.

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