This is not a riddle etc. but a serious question. It's a fact that when the sun is out humans are the only species who need to shade their eyes. A fact i've known for a long time but never heard a satisfactory explanation. Can anyone help?
133249
well, only primates have hands. But I doubt this is the case. How do you know it is a fact that humans and not gorillas, orangatans and chimpanzeess shade their eyes?Mark Twain once said " Man is the only animal that blushes, and needs to."
378311
Well the sun is forever burning,I don't think it would cool down at any point in time.\nI think thats how it is I'm not really sure,ether way they'll burn to a crisp.\nFried monkey!Thats a new one.lol
658942
Melanin comes in many shades of yellow, green, light brown, hazel, medium brown, dark brown and very dark brown, almost black. It is all melanin, so it is not IN ERROR. All of The Design is perfect and fine.  As far as a FUNCTION of the pigment MELANIN, nature intended it to be both PROTECTIVE against harsh UV rays and the associated carcinogenicity and decorative color variation!  The higher latitudes GENERALLY have the fairest people, the lower latitudes generally have the darkest, at least on the northern hemisphere where most of the planetary land masses and people are.  With our global transportation abilities, we humans mix around easily now, so the gene pools get mixed up more now.\n\nSkin and hair and eyes are protected more (the layers below especially in skin and eyes) when there is more dark shades of melanin, so in that way, darkest melanin is the most protective and superior, and is associated with those humans who are on the parts of the earth where the intensity of the sun and its harmful UV rays would be the harshest, where the humans are apt to have the least INDOOR protection or access to sun screen etc. But now the hole in the ozone is huge and even humans with darker pigments can still get cancer of the eyeball or skin from the harmful rays.  SPF factor clothing is becoming essential down under as most people know someone who died of malignant melanoma, so as there is bigger hole in the ozone from human disruption of earth's protective ozone, there will be more humans dying of melanoma and that too will shift the gene pools so that the "survival of the fittest" as far as skin color is concerned will occur.\n\nThat is, unless we humans kill each other by some other way. We could wipe ourselves faster than the process of classic examples of natural selection known on the earth. Germ warfare and nukes could change the gene pools real fast. And global warming is helping to contribute to weather changes that can cause huge-catastophic death rates all over the earth.\n\nWho knows who the next "top dog" would-could be if we wiped out half the population or more from our insanities, inc terrorism, or if Mother Nature dished out numerous powerfully deadly and HUGE "acts of nature."
619108
Eye composition is different from species to species\n\nSome animals do not have cones in their eyes, which allow other animals to see in varying degrees of color.  Humans have three cone types:  red, blue, and green.  However, other cone types have been found in various animals.  Some aquatic species have been examined to have many more, some as many as 16 different types.\n\nEye shape is another factor.  Birds have eyes that can focus more sharply on a point than other animals.  The back of their eye is flatter and larger, allowing for a bigger picture to be taken in through the lens and pupil.  \n\nSome animals barely have a developed eye due to their natural habitat, such as cave dwellers and some burrowers.  Instead, other senses make up for the loss of sight.\n\nThere are even cases where eyesight is only for observation of movement in the area.  In other words, stand still and you will not get picked up.  Rhinoceros eyes are like that.\n\nThe Pupil, which is where light comes into the eye, gets larger in darker environments to let animals get around in low-light surroundings.  The muscles which control the pupil size (dilator and sphincter pairs) are stronger or larger in certain animals, giving them the ability to open the pupil to the point where the Iris is barely visible around it.  Cats are a good example.\n\nSome animals can even see in the infrared and ultraviolet, but this again goes tothe types of rods and cones present in the composition of the animal eye.
230914
Eye color is believed to help protect your retina from the sunlight, but that's not really true -- it doesn't matter.\n\nYour iris is made up of fibers, and the colors vary, depending on your genetics. There's no real explanation to why eye color is the way it is.
283235
I think their light-loving behavior has to do with mating. \nYou see, in the dark, it´s very difficult to get together with individuals of the same species, so evolution came up with a great idea: a universal rendez-vous for insects. \nBy moving towards light, the chances of meeting a nice partner climb up. And that is directly related to an enhanced ability to reproduce, the ideal mix of features for any trait to get evolutionarily fixed in a population.
321520
Some people just naturally have darkness around their eyes. (I don't understand why people call them dark circles when they're not really circles) In this case, getting more sleep or eating better isn't going to help things, and neither will so-called "skin brighteners". The only thing that will really help is under-eye concealer. Use a shade slightly lighter than your skin tone, and set it with powder so it will last through the day.\n\nAs a last resort, if yours are really bad, they also have laser treatments available to lighten the skin in that area.
73188
+\nReal\n\nNo one really believes that the human eye developed from some other biological structure in one single generation, \nNo one believes the iris could have developed without a cornea, or a retina without a lens, or a pupil without an eyelid to protect it.\n\nEvolution of complex organs can’t occur in a single generation,  parts of organs cannot  evolve without the other parts. That is demanded by the concept of the survival of the fittest. Part of an eye gives no competitive advantage to one over another.\n\nEvolution of a specie is impossible!\n\nThe nest possibility is chance….   One day a man happened   without cause…..\nNot very likely\n\nThe last alternative possibility is that the spiecie migrated here from some other point in space or some other dimension.\nThat would still leave us with the question were they created…  and the same choices..\n\nYes creationism is real and the only logical possibility\nthere are many good resources
408764
They bite more when it is overcast for a couple of reasons, First is security. When it is bright and sunny they know they are exposed so they seek shelter. They don't seek shade! There physiological make up allows them to see clearly in all types of lighting situations, so it has nothing to do with their eyes. Also when it is bright and sunny, shadows are cast easily and this in return contributes to their skittishness. When you talking about flyfishing, the reason is the hatches, for one reason or another, always come off in greater numbers during overcast conditions. So when the bugs are on the water, the fish will be on the bugs!
245511
Nudists work up a tan just like anyone else. Sunscreen, exposure and shade when their skin has had enough sun. But because they don't wear clothes unless nature or society outside their group requires it, nudists also get wind burned which helps keep their skin tanned so they can withstand more sun.\n\nThink about driving your car with your window down on a cloudy day. You are wearing a t-shirt and your arm is resting in the window. Even though the sun is hidden behind clouds you can still end up with your arm looking sun burned from exposure to the wind.\n\nThe combination of sun and wind can keep their skin tanned longer so they don't need as much protection as a non-nudist does.
131394
I point out that "God made them" fails entirely to explain the situation.  Adam and Eve cannot contribute enough different versions of genes (four total, assuming no duplicates) to account for the modern diversity of hair color, much less the really complicated traits (over 100 different versions in some cases).\n\nAncestral humans were dark haired.  Mutant genes for different hair colors have occured at various times in history.  Caucasians seem to have several.  It's not clear why.  It's suspected that it may have to do with general color reduction to allow us to produce more vitamin D (I think that's the one we produce with sunlight).  Dark hair on the body would absorb light and keep it off the skin, just like melanin in the skin would absorb it and keep it from being used.\n\nThe people who lived in Japan before it's current ethnic group moved in had a red hair gene that was fairly common and still crops up on occasion in Japan to this day, though not at all often.
430316
Honey, I understand! Here is what I do, and I hate before I do it, but it works. When it is cold, dark, rainy, etc. I do not want to do a thing. I'd rather lay in bed or in the house watching TV and eating all day. But, we can lead a very productive life that way can we. So what I do is drag my lazy butt to the shower, get dressed, make-up and all, and go outside and just become part of what is going on. Really it helps. Something else that helps but I hate to recommend b/c it isn't good for your overall health, is artificial sunlight. However, if you put sunblock all over you and go lay in a tanning bed for 7-10 minutes, it'll perk you up a little, but not as much as learning to enjoy the day by doing something outdorsy no matter what the weather is like.
356247
Albinos don't like the sun. and people alergic to sunlight. plus vampires.
18423
You look at the sun directly, your eyesight goes DOWN. If you're blind, it won't matter which way is up on the Sun.  ;-)\n\nImran
144991
Brown eyes\n \nBrown eyesThe vast majority of the world's people have dark eyes, ranging from brown to nearly black. Light brown eyes are also present in many people, but to a lesser extent. Most of the original inhabitants of Africa, Asia, and the Americas have brown eyes. Brown eyes are also found in Europe, Oceania and North America, though within European populations they are not predominant to the same extent
258232
Short Answer: no need to develop pigments.  \n\nThe explanation: sunlight is harmful (ergo you use sunscreen) because of UV light, and pigments are produced by our skin cells to absorb the force brought on by UV rays, keeping your DNA from absorbing them.  If you're not exposed to sunlight, your skin doesn't need to produce and therefore doesn't produce much pigmentation, if any.  Same happens in animals.  If their permanent condition is as such, they eventually lose all ability to produce pigments simply because they can invest the energy on something that will give them the advantage to survive in their environment.  \n\nAs for blindness, you need light in order to see, and just like we can't see in total darkness, fish can't see in darkness either.  So, animals that live in absolutely dark environments don't need sight, and thus don't have it.  They'd rather spend the energy needed to develop sight (which is useless) in developing other sensory organs that will give them an advantage as hunter, to avoid being something else's lunch or both.\n\nMulti colouration in animals exists for many reasons, the two main ones are \n\n1- as disguise to fool prey (to eat) or to fool predators (to not be eaten)\n\n2- as an attractive feature for sexual selection, so that potential mates identify them clearly and select them for mating.  \n\nIn any case, competition to be the best hunter, the best hiding or the one that attracts more females or males drives selection and thus evolution.  \n\nRemember: if you get eaten, die of starvation or don't reproduce, you don't get to pass on your genes.  As such, any special traits you might have do not get passed on in the gene pool and those traits dissapear with your dead rotting self.  If more humans knew this, we'd be a little more appreciative of our uniqueness (read: selfish) and suicide rate would go way down.  \n\nThat's what evolution is all about, survive until you get laid and knock someone up or to get someone to knock you up.
284347
Dark skinned people have melanin in it. \nMelanin works like a sunscreen.\nThat's way dark skinned people have less skin cancer\nwile spending a lot more time outside.