So are trichromatic people colorblind to tetrachromats?
BTW. Wikipedia says that trichromatism was normal for mammals in the past, and then they lost one or two cones, which would suggest a different development path. The article does not touch on this.
Or did distinct cones were reduced, and then one of them split into two again? It's also interesting whether chemical structure of cones is similar. I guess I gotta do some research on my own.
Incredibly stupid experiment. As someone who is red-green color weak, just as 10% of the male population is, I feel insulted by the implication of this article and the obvious glossing over the fact that not all humans see green/red very strongly. This is lazy science, seriously asking people to differentiate between images of apes that want to mate? It made no sense, you basically proved that some people are colorblind... ok. Did you plan and write this over a weekend? Why did you even bother?
> Instead of having good vision, dogs, horses, mice, antelope – in fact, most mammals generally – have long damp snouts that they use to sniff things with. It is we humans, and apes and monkeys, who are different.
What a load of bull. Dogs and wolves eyes are facing forward, as do cats', owls', jumping spiders' main eyes, and generally those of most hunting predators. Eyes facing forward is good for depth perception and judging speeds and thus hunting, a bigger field of view is good for detecting threats from any and all directions and thus for prey animals. The location of the eyes depends mainly on where the animals sits on the predator<->prey scale. Apes tend to be apex predators, thus the predator eye location.
But our primate ancestors who originally evolved forward-facing eyes were not predators. Makes much more sense to think it was to help in swinging from limb to limb in trees.
Evolution is not straightforward. If a carnivore changes to a plant-based diet, chances are some carnivore traits are going to remain, if they are not too hardly selected against. See panda bears, fruit bats, ...
A testament to how important signal processing is: Despite its 22 different photoreceptors rather than the humans three (four if you count cones), mantis shrimp can only distinguish a limited number of colors as their brains do not mix the inputs from the different receptors, but rather just go with the strongest one to determine the color of an object.
As a colour-blind person, this article both makes sense to me, and at the same time it doesn't.
I have often wondered why human colour vision is not evenly distributed across the spectrum of visible light. This seems like a decent enough model for why that might be the case.
However, that makes it very peculiar that there are so many people with colour-blindness like me, especially if it would be such a strong evolutionary advantage. One would expect selection pressure to have removed those genes from the gene pool by now.
My own pet hypothesis is that it has to do with humans being a social species. For us, individual specialisation has much bigger evolutionary benefit, since it is shared, and a lower evolutionary cost, because other members of the group can compensate for shortcomings.
To give an overly simplified "economic" model of it: when we collaborate properly, the net performance of a group is not the average performance of all members, but the sum of the maximum performance of individuals.
So back to colour-blindness. It is fairly well-established that dichromatic colour-blindness helps see through certain types of camouflage. In a hunter/gatherer society, having one member of the group who is good at spotting prey animals (or dangerous predators, for that matter) is a huge advantage for the group, and your friends can assist you with getting ripe berries.
There is an alternative hypothesis. That it's just an evolutionary accident. Possibly it's a side effect of some other factor that is significant.
I mean, we get a lot of evolutionary traits because of bias through natural selection. But there's probably not much reason to lose a trait if there's no selection pressure to. It still may happen,of course. It's possible we'll all have brown eyes some time down the road. But it's not obviously because of natural selection.
Of course, there may be no strong selection pressure against it. But the odd bias for red-green distinction has been there from the earliest primates, suggesting there is a strong selection pressure in favour of specialising in red-green hue distinction. This then goes directly against having no ability to distinguish so many green and red hues.
Well, unless the only genetic way to maintain this bias includes a risk of colour-blindness, but I kinda doubt that.
Tangent: actually, eye colour is very strongly influenced by natural selection. Specifically, IIRC it's one of the prime examples of social and/or sexual selection pressure being stronger than other pressures, precisely because it has no other survival advantage/disadvantage associated with it otherwise. Since social success is essential for individual survival in our species, being discriminated against for ethnicity in general is a selection pressure (and before I am misunderstood: evolution is an amoral context-optimiser and Social Darwinism is one of the worst perversions of a scientific theory ever).
Do you realise that you are implying that sexual selection is in favour of light eyes in general? This was not what I stated.
I merely talked about differentiating in- and out-groups, which is localised, meaning the homogeneity of an eye colour within an ethnicity can be explained through sexual selection.
Regarding the prevalence of brown eyes, light eyes and hair are a recent and recessive mutation. That is all that is required to explain why it is localised and less common: it is limited to people who descended from the point of origin of the mutation. In this case that would be Northern Europe.
The other advantage is the ability to function in low-light conditions where everyone loses their color vision. Color blind people do not lose the visual cues in twilight. Colorblindness is much more prevalent in norther Europe, which has very long twilight, than it is than Africa and India.
>I have often wondered why human colour vision is not evenly distributed across the spectrum of visible light.
Instances of color-blindness is different between men and women. One reason hypothesized why women have lower incidence, is spotting infection and discoloration in infants.
Ehm, that is simply a consequence of the Y chromosome missing the genes for color vision, no? Or are you saying that this might be why those genes "fell off the cart" in the evolution of the Y chromosome?
i think the social species and specialization both plays a role, but we also have gender specialization. colorblindness effects 8% of men, but only .5% of women. maybe the men have less pressure to select ripe fruit / see social cues. i understand this is because of the x/y chromosome effect, but maybe since it barely effects women its not a strong enough evolutionary pressure to wipe colorblindness out completely.
> i understand this is because of the x/y chromosome effect, but maybe since it barely effects women its not a strong enough evolutionary pressure to wipe colorblindness out completely.
That is a fair point. A slightly less friendly interpretation of this would be that men are the expendable gender, genetically speaking.
> maybe the men have less pressure to select ripe fruit / see social cues
I don't think any gender escapes the necessity to read social cues. There might be differences in which one though, but we're veering into a political minefield of nature/nurture questions here.
For example: there is a famous experiment where people were asked to guess if greyscale pictures of faces (cropped to not show hair) were male or female. The twist was that each face appeared twice, with the only difference in being how high the contrast was (especially the lips, IIRC).
High-contrast faces were more likely to be judged feminine than low-contrast faces. Again, this says nothing about whether this gender perception was nature or nurture.
I have often wondered why human colour vision is not evenly distributed across the spectrum of visible light.
Daniell Dennett (I think?) had a good explanation of this:
Q: Why is the sky blue?
A: Because leaves are green and berries are red
That is: our colour perception evolved in a particular environment and is optimised towards doing well in that environment by contrasting things that we care about (in that environment).
The article would have been more interesting if they addressed the peculiar fact that half of all women and all of spiders are tetrachromats. It would be interesting to add the cones for additional frequencies into a genetically engineered monkey. I can imagine that having vision in the infrared and UV would make animals better predators (like Predator)
And then there is the mantis shrimp with 12 different photoreceptors[0]
As for genetically engineering an extra cone, they did that with mice, mainly to address the chicken-and-egg question: if you get an extra cone, does the brain learn to see extra colours? It seems like it would[1].
What you propose would be almost impossible to test though. Sure, you can test for distinction quite easily, but measuring the cost/benefit of it in evolutionary terms is a lot harder. There is a trade-off to make here in what perception the eyes and brain are optimised for, perhaps other forms of perception will suffer to the point of it not being worth it.
Also, bad news regarding UV: our cones can perceive it, but our lens filters it out, suggesting it has too many disadvantages. The main reason is likely because UV light creates too much chromatic abberration in a single-lens system, making it hard for us to focus properly[2]. This is not a problem for the kind of vision required by a honey bee, but it would be for humans.
The article made me doubt, so I called my dogs. All my dogs have the eyes clearly in the front, so I spent some time trying to find dog races with eyes on the sides on google Images. I found none.
It is not a good idea for your credibility that the first thing you say in an article is blatantly false.
It would be interesting to design a UI colour scheme specifically with this in mind, with strategic use of red vs green for focusing attention in a way that parallels the eye's natural biological tuning, as a similar approach to accessibility UI design for colour-blindness.
If anyone knows anything like that that's been tried I'd be really interested.
We already use colour schemes tuned to our perception. They naturally converge on them.
Have you never noticed how colour blind people always complain that so many interfaces use red and green as two opposing colours? Or how those colours are overused in carthography? Because we do.
I don't know if it is ironic or if there is something I didn't understand...
That's because you just described traffic lights.
Now, I don't think a lot of biological research have been done when deciding the colors of traffic lights, there is research about why they feel so obvious.
The idea is: Red is the most noticeable color, good for signaling danger or requiring attention. Green is distinct from red, it is also the brightest color, so it is good as a complement for red. Yellow is simply the intermediate between red and green.
Agreed that we probably end up on that naturally for things like traffic lights or danger signs, but I was thinking more interns of a full UI with that approach as an integral, conscious design consideration... based on more in depth and sophisticated study of replicating colour schemes in a natural environment in a broader sense.
37 comments
[ 5.0 ms ] story [ 28.5 ms ] threadBTW. Wikipedia says that trichromatism was normal for mammals in the past, and then they lost one or two cones, which would suggest a different development path. The article does not touch on this.
Or did distinct cones were reduced, and then one of them split into two again? It's also interesting whether chemical structure of cones is similar. I guess I gotta do some research on my own.
Boy that's some next level webpage design!
[1] https://aeon.co/ideas/the-red-and-green-specialists-why-huma...
What a load of bull. Dogs and wolves eyes are facing forward, as do cats', owls', jumping spiders' main eyes, and generally those of most hunting predators. Eyes facing forward is good for depth perception and judging speeds and thus hunting, a bigger field of view is good for detecting threats from any and all directions and thus for prey animals. The location of the eyes depends mainly on where the animals sits on the predator<->prey scale. Apes tend to be apex predators, thus the predator eye location.
A few snippets:
a compound eye, made of thousands of small units that each detects light independently
12 to 16 different photoreceptors in its midband
has six photoreceptors dedicated to...UV
incredibly sophisticated UV detectors
http://www.businessinsider.com/the-mantis-shrimp-color-visio...
I have often wondered why human colour vision is not evenly distributed across the spectrum of visible light. This seems like a decent enough model for why that might be the case.
However, that makes it very peculiar that there are so many people with colour-blindness like me, especially if it would be such a strong evolutionary advantage. One would expect selection pressure to have removed those genes from the gene pool by now.
My own pet hypothesis is that it has to do with humans being a social species. For us, individual specialisation has much bigger evolutionary benefit, since it is shared, and a lower evolutionary cost, because other members of the group can compensate for shortcomings.
To give an overly simplified "economic" model of it: when we collaborate properly, the net performance of a group is not the average performance of all members, but the sum of the maximum performance of individuals.
So back to colour-blindness. It is fairly well-established that dichromatic colour-blindness helps see through certain types of camouflage. In a hunter/gatherer society, having one member of the group who is good at spotting prey animals (or dangerous predators, for that matter) is a huge advantage for the group, and your friends can assist you with getting ripe berries.
I mean, we get a lot of evolutionary traits because of bias through natural selection. But there's probably not much reason to lose a trait if there's no selection pressure to. It still may happen,of course. It's possible we'll all have brown eyes some time down the road. But it's not obviously because of natural selection.
Well, unless the only genetic way to maintain this bias includes a risk of colour-blindness, but I kinda doubt that.
Tangent: actually, eye colour is very strongly influenced by natural selection. Specifically, IIRC it's one of the prime examples of social and/or sexual selection pressure being stronger than other pressures, precisely because it has no other survival advantage/disadvantage associated with it otherwise. Since social success is essential for individual survival in our species, being discriminated against for ethnicity in general is a selection pressure (and before I am misunderstood: evolution is an amoral context-optimiser and Social Darwinism is one of the worst perversions of a scientific theory ever).
Maybe, but then what’s your explanation for the prevalence of brown eyes due to natural selection?
I merely talked about differentiating in- and out-groups, which is localised, meaning the homogeneity of an eye colour within an ethnicity can be explained through sexual selection.
Regarding the prevalence of brown eyes, light eyes and hair are a recent and recessive mutation. That is all that is required to explain why it is localised and less common: it is limited to people who descended from the point of origin of the mutation. In this case that would be Northern Europe.
http://learn.genetics.utah.edu/content/basics/patterns/
Instances of color-blindness is different between men and women. One reason hypothesized why women have lower incidence, is spotting infection and discoloration in infants.
That is a fair point. A slightly less friendly interpretation of this would be that men are the expendable gender, genetically speaking.
> maybe the men have less pressure to select ripe fruit / see social cues
I don't think any gender escapes the necessity to read social cues. There might be differences in which one though, but we're veering into a political minefield of nature/nurture questions here.
For example: there is a famous experiment where people were asked to guess if greyscale pictures of faces (cropped to not show hair) were male or female. The twist was that each face appeared twice, with the only difference in being how high the contrast was (especially the lips, IIRC).
High-contrast faces were more likely to be judged feminine than low-contrast faces. Again, this says nothing about whether this gender perception was nature or nurture.
Daniell Dennett (I think?) had a good explanation of this:
Q: Why is the sky blue? A: Because leaves are green and berries are red
That is: our colour perception evolved in a particular environment and is optimised towards doing well in that environment by contrasting things that we care about (in that environment).
https://www.snopes.com/politics/medical/tetrachromacy.asp
As for genetically engineering an extra cone, they did that with mice, mainly to address the chicken-and-egg question: if you get an extra cone, does the brain learn to see extra colours? It seems like it would[1].
What you propose would be almost impossible to test though. Sure, you can test for distinction quite easily, but measuring the cost/benefit of it in evolutionary terms is a lot harder. There is a trade-off to make here in what perception the eyes and brain are optimised for, perhaps other forms of perception will suffer to the point of it not being worth it.
Also, bad news regarding UV: our cones can perceive it, but our lens filters it out, suggesting it has too many disadvantages. The main reason is likely because UV light creates too much chromatic abberration in a single-lens system, making it hard for us to focus properly[2]. This is not a problem for the kind of vision required by a honey bee, but it would be for humans.
[0] http://science.sciencemag.org/content/343/6169/411
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC208822/
[2] https://en.wikipedia.org/wiki/Chromatic_aberration
It is not a good idea for your credibility that the first thing you say in an article is blatantly false.
If anyone knows anything like that that's been tried I'd be really interested.
Have you never noticed how colour blind people always complain that so many interfaces use red and green as two opposing colours? Or how those colours are overused in carthography? Because we do.
That's because you just described traffic lights.
Now, I don't think a lot of biological research have been done when deciding the colors of traffic lights, there is research about why they feel so obvious.
The idea is: Red is the most noticeable color, good for signaling danger or requiring attention. Green is distinct from red, it is also the brightest color, so it is good as a complement for red. Yellow is simply the intermediate between red and green.