I formally propose that articulated eye stalks are the best structural for visual sensory organs. At least for land animals, and walking sea animals.
It’s a really good idea and I really wish humans had gone that route. I’m imaging a skinny trunk appendage with the housing for an eyeball. Take a chameleon’s eye, extrude it another 2”, give it several more degrees of freedom more like a short trunk, that’s the general idea. It’s a bit counterintuitive at first because there are cringe inducing severing hazards to having eye stalks. It’s hard to get past imagining going blind from the same mistakes that might otherwise only result in a pinched finger. It’s a bit like having a tail, there’s a heavy cost to maintaining the feature just due to it being so imminently breakable, so it better be worth it.
Increased fragility is the big drawback. That is a pretty big risk, but I think the advantages far outweigh it.
First off the most obvious. This is effectively a 360 degree binocular pan, tilt, zoom system, at a relatively low cost compared to having extremely large eyes or more than two. The motor coordination is more complex than eye movements necessary for just rotating skull locked eyes, but not overwhelmingly so. 6-10 extra degrees of freedom per eye seem manageable, though I have literally no basis for that other than it feels right enough. Though it would definitely demand much more of our visual cortex to process feeds from two independently moving eyes and variable fields of view. But a mammalian vision system modified to create stable, consistent images from two sensors with a wide range of independent motion would just be plain awesome.
The advantages are immense for anything that has to move in one direction while still monitoring other directions they’re not moving in for threats or resources. You have to sense the direction you’re moving in or you walk into or fall off stuff. Looking everywhere else is more optional, but the option of not looking is always risky.
The wide field of view might seem more advantageous for prey than predators, but moving stalks can change that 360 field to a narrow one with extremely accurate depth perception in an instant. And most predators are still prey themselves, often while they are predating, so being able to switch modes is pretty good for everyone.
I’d think there could be very unexpected benefits from correlating independently articulated moving eyes that we just wouldn’t even know about because no creature with anything near our brain structure has them. Maybe there is some useful environmental data that can be correlated by oscillating the interocular distance as the eyes pan. Or arranging the eyes vertically but upright in a top\bottom binocular configuration. I’m sure multi-camera vision processing algorithms would offer some interesting insight into the potentials of separate moving eyes, but I don’t know much about them.
For every advantage articulated eyestakes create, they introduce a dozen more potential failure modes. Besides the massively increased potential for blindness, there are probably some spectacularly weird ways for all that visual processing to go wrong.
So at this point it seems like eyestalks are objectively awesome, but still probably more trouble than they’re really worth. But that’s because we haven’t considered what you don’t need when you have eyestalks.
An appropriate eyestalk could effectively replace the necessity of necks. That’s huge. Necks are terrible, terrible structures. They are points of articulation that pass literally all the critical pathways of a body’s system. The fact that you have to move your head to move your field of view more than a few degrees just seems like one of evolution’s dumbest fails with horrific and far reaching consequences. Remove the necessity of an articulated neck to move your entire head, and those critical pathways can be stationary, much better protected, and far less failure prone. I’ll take the risks of blindness and crazy ocular disorders if I just don’t have to deal with this stupid, vulnerable, seemingly overarticulated but surprisingly limited, neck thing.
Stalks could provide a perfectly functional alternative to the entire face except the mouth. You can pop your audio organs on there and get all the advantages of binaural hearing, plus probably some really interesting signal processing potential from the independent positioning. I’m 50/50 on olfactory organs. Could put some on the stalks or not, might be better to keep those nearer the mouth though. Plus you put a nose on a stalk and it’s a trunk or an antenna. Eyestalks should be eyestalks.
And the identification and communication functions of a face could be done with sufficiently expressive articulation of the stalks. So now you don’t really even really need a head at all. You can pack your brain somewhere less precarious than the top or front. The best way to avoid head injury is to forego having a head.
You’ll need to find a place for a mouth, but there’s plenty of viable real estate. Could work those into a short, lip\trunk assembly or just an upper torso mounted sphincter with teeth that feeds straight to the stomach. Just having a head doesn’t necessitate breathing and eating through the same tube, that’s another nature fail. And you don’t really need to use the same air that interfaces directly with your blood to smell your environment, you could use some simpler independent bellow organ to move air over them. So it’s your choice if you do the one tube or two for breathing and eating. There’s probably some advantage in having fewer orifices to maintain though. In any case you just have a lot more options when none of the pathways have to pass through a stupidly articulated neck.
This all seems like a giant win for all land and sea bottom dwelling life. For fish and birds I’m not 100% sure all of this applies. Vision in general isn’t as effective in the water, so maximizing that sense may not be as effective as spending the energy elsewhere. And fish don’t really have vulnerable and complicated articulated necks, so there’s no gain there. Even aquatic mammals probably wouldn’t benefit much from the advantages of eyestalks. Unless if we considered the potential for articulated binocular sonar receivers, or even independent, directional ping generators and receivers, but today I’m talking about eyestalks. Also I keep mentioning walking sea creatures but I’m not sure why. Seems like walking shares the same features in either place, but the vision thing underwater works against it. I think I just included it because of stomatopods. They’re awesome and they have a lot of the features of the eyes I’m talking about, plus hyperspectral vision and other cool stuff, and somehow they’re so awesome I just think all sea creatures with legs should get an invite to the eyestalk party. Doesn’t have to make sense.
Birds, I just don’t think eyestalks would do much for them. They have the neck issue, but their neck articulation is pretty much 360 already, so they only gain real-time 360 vision and I’m not sure they even need that. They don’t really have as urgent a need to look in the direction they’re moving. If a bird in flight looks straight ahead and doesn’t see a barrier in the forward direction, it can look elsewhere for a reasonable amount of time without updating. Feet don’t really support a comparable autopilot feature. You can maybe close your eyes and walk across a salt flat or something similar, but most places on Earth you need to update your forward visual information pretty much constantly or something will remind you. Also seems like there’s a drag issue with eyestalks, there are workarounds but long protruding things just don’t seem conducive to graceful flight. Bats fall in the same category as birds, but they already look insane and their flight isn’t graceful at all so I’m thinking give bats eyestalks for the hell of it and see what happens.
So I think I’ve made a fair case for the awesomeness of eyestalks in general. But I’ve got a bomb to drop on nature if I could ever figure out how to drop it. That bomb is called retractable eye stalks. I think that would just break evolution entirely. You’d be unstoppable. Might be a little hygiene issue keeping your stalk cavities clean, but it’s a fair price to pay to keep your eyeballs attached.
Of course the real question is how much biological energy the eyestalks cost vs how much they save or help acquire. I have zero credibility to make that calculation, but I’m not making a calculation, I’m sort of rationalizing a hunch, which is more fun and pretty much all I’m capable of. So that’s my spiel about eyestalks.