Matterwave said:
Physics actually can contribute here. They are too small.
To resolve things through a lens of size ##D##, the angular resolution limit estimate is ##\theta\approx \lambda/D##.
If we plug in values for our eyes (pupils) we get roughly 1 arcminute. So at a meter we can resolve things about 0.2mm apart. A typical bacterium is 1-2 microns (0.001-0.002 mm). To see a bacterium at 1 meter we'd need eyes 100x bigger. A virus is even smaller, in the sub-micron scale so that's even worse. This is not factoring in anything related to focal length. And minimum resolution just means "I can see two dots instead of one".
But of course, if a lot of bacteria pile up, we can see the colonies. Have you seen a bacterium culture in a petri dish before?
This is a little advanced for me. Would you mind breaking it down? Let me know if you need to know where you lost me.
Never seen bacteria in a petri dish... would be so fascinated by it, I'm sure. I'd probably also stop drinking water after I see living things in it.
pinball1970 said:
We evolved to see prey, mates, competitors, things we understand as danger.
There are physical limitations on small things as matter waves explanation of the human eye.
We can still smell, bad odour can mean rotting and spoiling. We all recognise certain aspects of smell including death and we would have been much better at it 1000s of years ago before we had morgues and funeral homes.
So how things/food and water look and smell would have given us some warnings.
That's true! But the thought really crossed my mind as I was thinking about how we didn't know about bacteria's existence for so many years, and I'd imagine how many deaths we've prevented since learning about them. I just kinda feel like the 'disgust' response isn't quite enough. For example, I'm typing this on my keyboard which I'm sure is extremely dirty under all the keycaps, but I don't feel disgusted. That goes for so many things. Think about how often medical doctors wash their hands just because they
are aware, or at least their profession really forces them to be. Wouldn't it be some sort of advantage if we could detect them on things we don't normally find disgusting and then make a judgment about whether or not to do something about it?
Were we really better at smelling death and recognizing scents years ago? Never heard of funeral homes and morgues making that obsolete.
pinball1970 said:
Most microbes are harmless, many that are not we can deal with and some are opportunistic. There are microbes covering our skin, mucus membranes, hair and teeth. That's just on the outside.
Imagine seeing all of the staphylococcus sp all over your skin? All over a mates face and hair? Before kissing her? Probably run a mile!
Evolutionary limits on the physiology of the eye spared us some unpleasant biology.
I'm sure it does, but let's imagine we can just see the dangerous ones, and let's imagine we have the ability to consider whether or not to act and still kiss. We all take risks in daily life, despite knowing there's potentially danger. I guess I'm more so arguing in the sense of needing something to remind us of the dangerous ever-being there, as a real threat, as opposed to just this abstract knowledge that kissing and such involves X amount of bacteria, because that's different from having, say, an instinctive system in your brain that detects it. If that makes sense? Something that doesn't require us to learn biology first or actively be disgusted the whole time.
DaveC426913 said:
We can do that a lot better than seeing them. We sense their by-products with our noses.
Noses were the first sensory organ to evolve because that's the one that finds food and avoids toxins.
The question is more informative if we turn it on its head: why, if our primitive ancestor can already smell what to eat and what to avoid, did they need to evolve eyes?
I feel as though it doesn't work all the time. As I've described in this post; there's tons of things we do in daily life that has dangerous bacteria without my brain telling me about it. Oh, and from personal experience I've eaten stuff past the due date because I didn't smell it, haha. How would you explain situations such as those?
BillTre said:
To get more information about one's environment (in a tradeoff with the costs to the organism for getting that capability).
In a SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis, its an opportunity.
Vision gives rapid warnings of distant threats and alerts to distant opportunities.
This is very helpful. Thank you, I didn't think about it in the tradeoff way. I talked to another friend about it and he said that if our eyes have to become a microscope, we'd stop seeing anything else.
256bits said:
And yet. incidents of pedestrians trusting their judgement and getting hit by a moving vehicle does happen.
Deer and moose seem to dart out in front of moving vehicles. They know the vehicle is something, maybe it is moving towards them due to sound, but visually there are few clues to what the vehicle is doing and how fast it is travelling - no car head movements or running legs.
People do the same - they see the car, process something in their brain for some seconds and then dart out in front and get hit. Judgement was not working.
Sorry, I don't think I explained it very well. I thought people might respond saying: ''but then we'd never want to touch or eat anything because our instincts would prevent us!'' so I pre-emptively made the argument that inside this hypothetical, we could always have a choice, much like how we have a choice to cross the road or not, even despite knowing the danger of cars rushing by exists visually in front of us.
256bits said:
There is no dedicated jay-walking processing centre within the brain. If there was one, you would have to eat more to supply energy to keep the centre functional. In which case foraging for longer periods for food brings extra risk of becomming prey yourself.
And would make us get hit by cars more often when we forget to eat, I guess.
256bits said:
If the eye has evolved to see smallish things such as bacteria, the brain would have to keep up with extra visual processing trying to discern the different types of bacteria. That would take extra energy needing extra foraging, with accompanying extra risk of becoming prey, inter species conflict, injury, or starvation during scarce food supply.
To keep brain energy levels down, perhaps instead something else would have to give such as taste and smell. Perhaps the creativity and adaptable tool use of the brain could go. Rather than a human looking and acting the way you do now, you would be a saucer eyed creature wolfing down food like a dog does without the favourable sensations that smell and taste provide, or just a simple creature looking around at bacteria, which are everywhere and unavoidable, for whatever reason.
That's true. I didn't think about the energy costs. I'm fascinated by how little food we actually already need for how much our brain and bodies do. I suppose I didn't consider evolution as something that comes at a cost when the thought came up to me - but the fact that we've been fighting bacteria and viruses for ages made me wonder about why we just haven't yet.
256bits said:
Odd about pets and how they evolved a bit differently.
Cat - sniffs at new food, walks away = i don't like it.
Dog - stinkiest morcel of rancid food = this is great! ( They will even enjoy rolling on a decaying animal carcass )
Dogs do what? Don't they die from eating spoiled food?
Bandersnatch said:
Whenever this question comes up, it's important to weigh the cost of developing a trait against its advantage - and not just for the final trait, such as the huge bacteria-discerning eyeballs we're considering here, but for every incremental evolutionary step along the way.
For example, a woodpecker's tongue is freakishly long, helping it reach grubs in their holes. But it didn't need to get to the present length to become advantageous - every past woodpecker with a tongue longer than its ancestor would have been able to access a little more food, at the low cost of having to grow a slightly longer muscle. Thus any lengthening of the tongue was justifiable from the evolutionary perspective.
Hey, thank you for this helpful and long reply.
Also - love your username. If that's a Black Mirror reference.
Bandersnatch said:
So we need to ask whether having increasingly large eyes would keep increasing the fitness of members of a population. Since it wouldn't help any in seeing those bacteria until we get to the upwards-of-1m-across eyeballs that matterwave estimated, eyes smaller than that would still need to somehow help us procreate more,
Does everything in evolution 'check' against whether or not it helps the species procreate? Because technically, us not dying from bacteria would help, but I don't know if 'evolution' can look at it this way. I honestly don't understand how it knows what to evolve and what not to in the first place. I heard it's somewhat random and the 'good' traits survive.
Bandersnatch said:
at every step of enlargement, while at the same time incurring costs in the form of protein investment [need to eat more to develop and maintain an enlarged body part], developmental risk [passing through the birth canal is hard for humans already], and mechanical disadvantage [lugging bigger eyes around takes extra effort].
It's hard to, uh, see where the required advantage could be in this case.
I see! (Pun not intended).
BillTre said:
Bacteria can be seen in a light microscope, but viruses can not because they are too small to resolve optically. Smaller things are scientifically visualized using different technologies like electron microscopy or atomic force microscopy. Eyes don't do these things and can't see the really small things. Microscopes and their associated procedures are made to emphasize the factors (many already mentioned) to optimize your viewing pleasure.
It seems to me that a big aperture eye able to see something as small as a bacteria would have a very small depth of field (like a microscope). This would reduce its usefulness to animals.
Various animals have a variety of light receptors for UV, polarized light, a variety of different wavelengths. Don't know of any contrast optics.
Some invertebrates (with their weird compound eyes and multiple eyes) have up to 12 different colors. Some of those colors may be for specific purposes like finding a mate in an unusual visual environment. With different eyes, some may be specific for particular purposes (like perhaps mate detection).
I see, thank you for the reply!
BillTre said:
Time constraints (time to sum photons to assemble an image of a moving object) can also limit what can be seen.
Oh, never considered this, that's fascinating. I sort of learned about this when I asked why I should have my monitor to be 120 FPS if my eyes 'can't see that fast.' He said it's because other parts of my brain still process what's happening and that's the difference I feel when I'm gaming. Unsure how true this is, it was ages ago.
OmCheeto said:
I'm not sure I understand why we would need large eyes. Going over the history of microscopes I rediscovered
Antonie van Leeuwenhoek, the guy who kind of invented them. It looks as though his design is being used in those inexpensive handheld USB microscopes. I think a biological version would fit comfortably in modern human skulls. But the more I research the idea, the less feasible it seems.
One expert in microscopy stated that bacteria are basically colorless. I'm guessing if we could get a decent image of one it would look similar to a tardigrade, mostly transparent, and visible via refraction, reflection, and lensing. There is also the problem of how small they are, and the details necessary to identify them might be available only when they are illuminated by UV light. Another problem is that both your microscope eye and the bacteria would have to be locked in place relative to each other. If you've ever used one of those handheld microscopes you will discover that it is nearly impossible to hold them by hand steady enough to see anything.
Anyways, I was trying to imagineer a machine that can see bacteria in the air, and then convert it into a biological system that would fit into our skull. It is definitely beyond my ability to even start to comprehend how to contruct the non-biological device.
This is a really helpful response, thank you.
