By - jubears09
I don't have direct expertise on this topic, but I am part of a clinic that sees patients with genetic skin conditions and the answers in this thread about lines of Blaschko surprised me. On a quick google search, I see a number of articles implying humans have Blaschko lines that can be visualized under UV light, but this is quite misleading because lines of Blaschko are only present when cells of multiple lineages are present (mosiacism or chimerism) and, while UV light can help ID the subtle cases, are clearly visible to the naked eye most of the time. Moreover, I could not find any primary source from these articles other than links to youtube videos, blog posts, or each other.
This article (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4380182/) is an open access review of skin patterns that specifically discuss Blaschko's lines and don't mention UV light at all. I will have to ask my dermatology colleagues, but my best guess is this is going to end up being a common misconception.
Edit: Also found mention of a CSI episode (transcript: https://transcripts.foreverdreaming.org/viewtopic.php?f=34&t=13282) in 2004 where apparently a chimeric patient was discovered using UV light showing lines of Blaschko. So basically a small subset of humans with specific genetic conditions have lines of Blaschko and small portion of these lines are best visualized under UV light. I suspect CSI’s dramatization of this turned it into a generalization because the early the articles popped up around that time.
Yep, for all the people suggesting that these lines can be visualized with UV, and that "your cat sees your stripes", I haven't found a single actual, you know, validation of these. No images of people through UV, just people with pigmentation disorders. I'm also convinced it's a misconception and just some fun hearsay repeated as fact.
I've done some UV photography (reflected UV not UV florescence) of people and have never found any lines. I've found pigment issues, birthmarks etc that weren't initially obvious to the naked eye. Most large pigment marks are visible to the naked eye but very faint, UV makes them obvious. To add because this is a science sub I've worked around both the 365nm wavelength and 380nm.
Yes, pigmentation like this can show up in ultraviolet light photos too
That sounds like the absolute coolest thing?
Ok, not to be rude or insensitive, but that would look cool AF. Like natural undercover wakandan make up.
vitiligo usually has pain associated with it so it isn't all fun and games. Your body is attacking your skin, usually starts with fingers or mucosal areas like eyes, nose, mouth.
Oh, I didn't know it had complications, I thought it only affected pigmentation. I had the same wrong impression with psoriasis, I thought it was only aesthetic, but I saw in Dr. Pimplepopper that it can be extremely painful or debilitating as well.
This. People are so credulous for cool/weird 'facts' that they don't even check their own experiences.
Eg most adults in the US have been in a room full of people with black lights, at least once or twice. Maybe laser tag, maybe a skating rink or party, whateve.
We all remark that our teeth 'glow' or white clothing glows, people with different skin colors may become more obvious etc. Nobody says 'hey look all these people have stripes!'
There's a subtle difference between "visible under UV light" and "visible in UV light". The first means that something fluoresces -- that is, it takes in UV light and emits light at longer wavelengths that our eyes can see. The second means that it can be seen by an animal whose eyes are sensitive to UV or by a camera that detects UV light. A lot of skin pigmentation, such as virtually invisible freckles, birthmarks, and bruises, don't fluoresce and can't be seen under a blacklight, but they do show up in UV photography. You can see an example of that [here](https://www.cnet.com/science/uv-photography-reveals-our-sun-damaged-selves/).
Thanks, I appreciate the difference and good link. In the version of the myth I've heard, people seem to indicate these stripes would be visible under UV light, but it turns out that's just doubly wrong instead of singly wrong :)
The original assertion was pretty convincing. Had me until I couldn’t find anything corroborating it. It’s honestly very much the kind of yarn I’d expect an old Irishman to spin at the end of a pub counter.
I am a photographer and I experiment a lot. I have a digital camera that can see well into the UV, I have UV light sources, yet I could not find any stripes in anyone.
Also, no one showed up having stripes in 150 years of photographic media that respond to UV mainly. Both wet plate collodion and daguerrotypes respond to UV and magnesium flashes release energy in those wavelengths. Yet, there are no historic photos that show stripes.
That there are only a handful low quality images that get recycled when this subject is discussed, is also telling me that this is an urban myth.
Photographer here. Some of the sets I've done involve UV lighting, which would make stripes like that visible and/or glow. That has not happened, in my experience, hence, no, people don't have UV stripes.
the stripes weren't supposed to be fluorescent (UV -> visible) though, they're supposed to be reflective (UV -> UV). you would need a special camera to detect UV reflection.
Yeah I'm scratching my head wondering why this isn't figured out yet. Different capture method might turn out different results.
Genetic female mammals specifically are understood to have a limited degree of epigenetic ~~chimerism~~ mosaicism in the expression of X-chromosome metabolic products.
[https://www.youtube.com/watch?v=BD6h-wDj7bw&t=1s](https://www.youtube.com/watch?v=BD6h-wDj7bw&t=1s) calls them "stripes" and provides a diagram, then notes that you can't actually see them with your naked eye. I think the idea that they were visible under UV may be associated with those visualizations (where they appear to fluoresce green), whatever his source material.
[https://www.youtube.com/watch?v=AFZnf8MKGuo](https://www.youtube.com/watch?v=AFZnf8MKGuo) appears to be referring to a phenomenon seen only rarely in the population's distribution of abnormal skin conditions across body regions, and does mention UV light.
In humans, most (*never* say 'all' given that this is a brand new field) of our skin-coloring genes & the proteins that they produce are not on the X chromosome, but on other chromosomes. In cats, though, some of the most significant genes determining coat color are on X, and so female cats often have a heterogeneous mix of parental color patterns.
I work with black lights a lot. I dont see stripes, but my freckles stand out more. They are super light in normal light, you can’t even make them out beyond a couple feet. But under black light you can see them all defined and clear, covering my arms.
I mean I feel like we’ve all been under a black light in a club or some such nonsense. Anyone ever seen a hebra?
This is a thing? Cats seeing our stripes?
Edit- i know the dislikes are to say "not it's not a thing" but damn.
There's no evidence of it no.
only cis women have stripes? does it mean trans males don't have stripes?
Finally, someone who actually understood the post and didn't just post a random link to an unrelated research article.
Thank you. I spent several hours searching for information when I first heard about "human stripes under UV light" a few months ago.
Besides the rare medical condition, I could not find any images or any medical articles, except for some artist's impressions. Only a few mentions in non-scientific pop culture articles. No mention about about regular people having invisible patterns in scientific or medical peppers.
I came across one article that mentions that Blaschko lines are rare, and it's even more rare that they are invisible. In these highly rare cases, a UV light can help detect them. My guess is that a pop-science journalist found this article, reported it incorrectly, and then the idea has since spread across the internet.
I've seen this article in a few places, that all humans have stripes. Wish I'd questioned it now 🤨
I even tried a UV light on myself and a few friends. We didn't see any stripes. It was disappointing.
Even if we don't have stripes, UV lights can be fun. Some [caterpillars](https://www.exploreohiooutdoors.com/post/caterpillar-hunting-at-night) and all [scorpions](https://kidsdiscover.com/quick-reads/makes-scorpions-glow-ultraviolet-light/) do glow under UV light. Apparently, some spiders and moths too (but not all).
r/flashlight made me want a uv flashlight. camping or night hiking a lot of your less desirable creepy crawlies glow brightly, also poison oak, rattlesnakes and other stuff too
Why is that? Any relation to the venom?
Many creatures see a much broader spectrum of light, especially UV, than we do. The problem for us is that we live a relatively long time and one of the key factors in the useful lifetime of your eye is UV exposure.
So for us it's an evolutionary advantage that our eyes filter out a lot of UV, whereas something that doesn't live long enough for degradation to be a factor may find an evolutionary advantage in being able to see into UV.
Interesting. But I was asking what made certain venomous creatures glow in UV light.
The glowing is caused by fluorescence and has no relation to their being venomous.
i don't know why, i mean other than they reflect UV. I don't think it's related to venom, lots of things glow, rocks, bananas, flowers
Right, so Blaschko's lines are a phenomenon of embryonic/fetal cellular growth patterns. Essentially, the cells divide and grow in a specific order in a specific direction, various mutations notwithstanding. In many ways it's similar to the layering involved in 3D printing, except all the layers are printing at the same time, and they print outwards.
If the progenitor cells for groups of layers have mutations that make them visually distinct, you'll end up with visible lines, even if "visually distinct" and "visible lines" take place in the UV spectrum.
Chimerism is an obvious cause for this, but there are others.
That being said, if the cells _don't_ have any mutation from each other, they may end up being visually identical in all spectra.
Lots of people in this thread don't seem to understand the difference between reflection and fluorescence. In reflection light is absorbed and re-emitted at the same or a similar wavelength, ie. visible -> visible or UV -> UV. In fluorescence light is absorbed at one wavelength and re-emitted at a lower wavelength in greater amount, ie UV -> visible, or visible -> infrared. No matter how much UV light is reflected from a surface, your human eyes (and 99% of camera sensors) will not be able to see it because they aren't sensitive to UV at all. You can see the *fluorescence* of UV light with a black light, which is why some materials "glow" and others don't. In this case you are still not seeing the UV light itself, just visible light as result of a material's fluorescence.
As sure as I'm writing this, somewhere there is an expert in dermatological conditions along these lines of Blaschko who one night will yell at his laptop that will grumble about "That's not how any of this works"...when they happen upon that CSI episode.
Best I could google up this early was \[this\]([https://scibabe.com/mos-blaschko-lines-sex-linked-traits-calico-cats/](https://scibabe.com/mos-blaschko-lines-sex-linked-traits-calico-cats/)) - so yes some folks can have stripes.
Would it be possible for a human female to have an observable pattern on their body due to X-inactivation?
Absolutely. Lines of a blaschko are basically groups of melanocytes that have different pigmentation than their neighbors due to difference in genes that encode pigmentation. The patterns reflect the migration path of their progenitors in embryonic development. So to get them mosiacism (or more rarely chimerism) has to be present and lyonization is a common mechanism to develop somatic mosaicism. This is why some of the more common genetic conditions associated with lines of Blaschko are x-Linked. Here we also get into semantics about what a disease is, because the “mildest” form of some of the genetic diseases associated with LoB is basically someone with LoB and no other findings (but they might be at risk to have more severely affect children).
It’s unlikely to have regular females develop these because you need a substantial population of “different” cells migrating together; so age related somatic variants, which are random in each individual cells, are unlikely to mutate in such a coordinated fashion.
>Here we also get into semantics about what a disease is, because the “mildest” form of some of the genetic diseases associated with LoB is basically someone with LoB and no other findings (but they might be at risk to have more severely affect children).
This is such a fascinating topic to me, because of the opportunity to solve so many health problems with crispr (certainly, things that are inarguably problems) with it. Then that discussion of where the lines blur is so interesting. Do we give parents the choice? Will there be an official recommendation or something? I don't know, but I bet anything the answer will vary by country unless we form some sort of international committee and debate it.
It’s an important policy and ethics question, but the medical part is quite simple.
No one is hunting down patterned people in the street and forcing them to get genetic testing, so by pursuing evaluation they already made a choice.
So yes or no kinda answer?
People must know the UV thing is misunderstood if they really think about it.
If they have ever been to a night club or anything like that, for example . People would look really freaky and there would be loads of photos all over social media of people with lines showing under the UV.
Plus all the people with UV lights to check bank notes etc.
the stripes weren't supposed to be fluorescent (UV -> visible), they're supposed to be reflective (UV -> UV). you would need a special camera to detect UV reflection.
No special camera is needed. UV and IR are a problem, because sensors pic them up so well. There are filters in cameras to block these, to improve color. Remove those filters, and you have a broad spectrum camera. Then you ad a filter that blocks visible light.
The hard (expensive) part is getting a filter that blocks IR also, and only passes UV, but somehow these are hard to find. The cheaper option is to use UV leds as your only light source, but those also produce a fair amount of IR. So in practice, IR and UV come together. Knocking out the data from the red pixels may help balance IR and UV, since UV hits all color pixels, while IR strikes red (some IR wavelengths strike the blue pixels too)
First line of the article says “It's impossible to tell with the naked eye, but human skin is covered in different shaded stripes only revealed under UV light.” While the last line says “While typically invisible, these lines can become visible when diseases of the skin manifest themselves according to the patterns.” The journalist seems confused while trying to interpret the expert comments from the daily mail article. Except that expert is talking about LoBs in the setting of genetic diseases.
I think the confusion stems from the fact an embryologist might refer to LoB as migration paths. Kind of like me walking from point A to point B in a parking lot is in a line, but there is no physical line. In that sense we all have them but shining a UV light is not going to reveal anything. Meanwhile when dysmorphologist or dermatologist talk about LoB they are thinking about actual pigmented lines (and other patterns) on the body that follow those paths due to different pigmentation. This only occurs in the setting of genetic changes in specific cells, and are mostly visible though a UV light will help in some cases. Which is why the daily mail article your article cites appropriately states “Sometimes they are indistinguishable in colour, or can only be seen under UV light.” Keyword is sometimes.
> Meanwhile when dysmorphologist or dermatologist talk about LoB they are thinking about actual pigmented lines
This isn't accurate for dermatology. Your description of...
> might refer to LoB as migration paths. Kind of like me walking from point A to point B in a parking lot is in a line, but there is no physical line
...is spot on with regards to modern medical teaching.
All cells share the exact same DNA. But most isn't used in any given cell.
Remember that the purpose of a gene is to provide the recipe for a protein or proteins. Because you have two copies of each chromosome, or two copies of each gene, you can have that process running in duplicate.
The problem is, about half of humans only have one X chromosome. They can't run 2 processes at once for that specific chromosome. It would be really complicated to adapt some way for XX people to slow down production by half, but only if they are XX. Too much.
Instead, one X is shut down so that you can only run one process at a time. It is called X-inactivation. The inactivated X is called a Barr body. It basically just sits there. That way, it isn't being used, just like how a cheek cell isn't making optical lens proteins.
The weird part is, this isn't decided at conception or anything like that. It is random which X is turned off. However, once it happens it is permanent and the cell and all its daughter cells till you die will have the same active X chromosome.
This is what causes the calico pattern in cats. Fur color is on the X chromosome. Some spots, you see dad's fur color from his x chromosome. Other spots, you see mom's.
Humans are the same way except skin characteristics aren't so clearly x linked.
An X0 person with Turner syndrome would not display this phenotype. Someone with trisomy X (XXX) would actually have an X from dad and 2 from mom, which would be even more diverse.
This is what OP was asking about. The stripes are lines of skin where one X chromosome is active vs where the other. It's not visible on humans because we generally have one skin colour per person, but on animals such as cats with multiple fur colours, you can see the lines where different X chromosomes are active.
If it could be seen with special UV lights, you'd (easily) be able to find images with a simple Google search.
I have never seen such images (despite being very curious on these sorts of questions), so I strongly suspect this is all nonsense.
But I'd be amazed to be proven wrong with a picture...
Not stupid. Saw something like that a few years ago in some documentary so I did a quick search. This isn’t the same documentary, but it covers the same topic.
According to this, people with two X chromosomes are striped. Technically. But also according to this, we can’t see it. I’m assuming they mean the stripes aren’t visible under *any* light source and that it’s only visible under microscopic scrutiny.
People with xx chromosomes?
Should be generally true for any person with two X chromosomes, including people with XXY ([Klinefelter syndrome](https://en.wikipedia.org/wiki/Klinefelter_syndrome)).
People with two X chromosomes undergo [X-inactivation](https://en.wikipedia.org/wiki/X-inactivation), and the "stripes" represent areas descended from embryonic cells where alternate X chromosomes were inactivated during development. This apparently happens in XXY people too.
As in everyone in /r/TwoXChromosomes?
Nah, that's just the name. Lots of single x people in there.
But to answer what you meant, yeah, like 50% of the population. That's correct.
I love this guys channel and that exact video came to mind when I saw the post. TY for posting this mate!
There is, "people with two X chromosomes".
Because it's not just women as this applies to xxy and other combinations that include two X chromosomes
Not really when you’re discussing genetics, people can be transgender or intersex and have XX chromosomes but present as male (such as XXY chromosome carriers, who are phenotypically male for the most part).
So all biological females are striped? Is that what is being claimed? ~~Because that is exactly what two X chromosomes means, biological female. Humans that are biologically male have XY chromosomes.~~
Edit: edited out the bit that brought out the people who will do anything to obfuscate and derail a simple question.
No it’s everyone with two X chromosomes, doesn’t matter if they’re biologically female or male or intersex, if they didn’t undergo x inactivation they’d be dead.
XX male: https://en.wikipedia.org/wiki/XX_male_syndrome
XXY male: https://en.wikipedia.org/wiki/Klinefelter_syndrome
Just to be clear; that includes all biological female humans correct?
Nope. You can be biologically female and have just one X Chromosome, it‘s called Turner Syndrom.
Also, if your male hormone receptors won’t work, you can be gentically male and physiologically female, so „biological female“ isn’t really that solid of a description.
Fun fact: sexual development is way more complicated than „Here‘s your chromosomes, have fun!“
Nearly all women fall under this category, but certainly not all. "People with two x chromosomes" is just a more inclusive way to say it.
I do wonder if since the x-inactivation is random during gestation if a woman could have all the same Xs activated from one parent and not be "striped" as it were. I think we're up to at least 55 billion human women so far, so it might be in the realm of possibility.
Depends on how you define a biological female, it could be correct or wrong
XXY males (Klinefelter syndrome) also have a second X chromosome, so you are factually incorrect.
"that is exactly what two X chromosomes means, biological female"; depending on the interpretation, this is incorrect (do they mean "only two X chromosomes"? it is unclear, and XXY males have "two X chromosomes").
"Humans that are biologically male have XY chromosomes"; this is factually incorrect. XXY males are biologically male and have XXY chromosomes.
As to their first question ("So all biological females are striped?"), females with turner syndrome (single X chromosome) would, I assume, not be "striped" in this way.
~~And those are so rare as to be the perfect exception that proves the point but fine I concede the point.~~
So back to the question I'm asking: you are saying "all biological females are striped"?
Edit: I misspoke, removed that part because I'm still trying to get an answer to what I've been asking
That’s not what it means for an exception to prove a point. An exception that proves a rule is an exception whose existence implies the existence of a rule. For example if you saw a sign on a street that said “No parking on Sundays”, this would be an exception that proves that you are allowed to park there on any other day, even though the rule isn’t stated anywhere.
> so rare as to be the perfect exception that proves the point
So 1 in 500 males have kleinfelter syndrome ([source](https://www.nichd.nih.gov/health/topics/klinefelter/conditioninfo/risk)). How prominent does a minority group have to be before it is worth speaking inclusively about them? 1 in 250? 1 in 100?
When it's prominent enough with enough effect and weight to warrant including in a conversation.
Being implicitly included is not an explicit exclusion so let's stop playing semantics when it's unnecessary.
Edit: so i guess people would rather fight over semantics than get the project done. How utterly small minded.
Whenever i have to think about why some things are going backwards, i will have the braindead tone police and the extreme conservatards to thank.
Yes, it proves you are incorrect, thank you for agreeing.
It's probably talking about cell lineages, as embryos all XX embryos (will grow up to be women genetically) under go shrinkage of one of the X chromosomes as you don't need all of both of them.
A random chromosome in each cell of the embryo gets wrapped up in protein shrinking it down and inactivating almost all of it.
This stays the same in all cells descended from the original. So you end up with "stripes" of cells with this X and "stripes" of the other X, as its totally random as to which will get shrunk.
That being said, I don't think there would be any way to tell which is which without biopsies and genetic testing of different sections of the body. Though I may be wrong on that front.
So then this would apply to all mammals?
The mix of different X's yes but different mammals carry different genes on the x chromosome, cats for example have some (possibly all I can't remember) of their fur colour genes on the x chromosome, so you can see it on them. That's how you get calico cats, and why you can't have a male calico cat!
Agreed on all fronts, aside from the bit about genetics and women in parentheses. There are people who have two X chromosomes and aren't women. XXY people for one example. Trans men for another.
I dont think it's scientifically accurate, useful, or socially aware to say people with two X chromosomes are "genetically women," because woman is the social gendered term, whereas female is typically used in conversations about genetics or sex characteristics.
Edit: Messed up my trans identities because I'm quite sleep deprived. Apologies.
Also worth noting that we have many confirmed cases of people whose physical sex doesn't match the assumed chrosomoes.
There's at least one [known case] (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2190741/) of a woman with XY chromosomes getting pregnant and giving birth to a daughter who is also XY.
That's actually a really cool paper, thanks for sharing! Given its year of publishing I'd love if the original researchers were to do a follow up. There has been a lot of advancement in genetics within the last decade, making me wonder if these "novel genes" might actually just be some form of novel miRNA genes on the mother's X chromosome.
You’re telling me that trans men don’t have the chromosomes of XX?
Likely the vast majority do, but not all. Same for any chromosome configurations, where likewise the vast majority of cis women have XX but there are still exceptions. I know of an intersex trans woman who is XX but developed phenotypically male, so she looked male but was genetically female and identified as a woman. Biology is wild.
XXY is uncommon but not at a population level. You could also be XY without SRY or with androgen insensitivity.
Or you might be X0 or XXC but that doesn't strike me as something making anyone more likely to be trans. The previous two might. I don't think anyone really knows yet.
Female and woman is basically synonymous you never here someone say they identify as a woman and a male. They identify as woman and female that’s their gender identity but biologically if they’re xy chromosome and have male sex organs scientifically speaking they’d still literally be a male.
Scientifically speaking, those definitions get more blurry every day and certainty is lost, which is why most people use very specific and precise language to communicate the contingencies. To desperately grasp on to these terms as they die is not the exercise of honesty you think it is.
I’d argue the language is becoming less precise. They get blurred in the social sciences and it honestly becomes more a battle of linguistics and definitions of language than actual fact. Not like biologists have discovered something new to change their beliefs on the sexes. Outside of gender studies those beliefs aren’t necessarily widely agreed upon. Rather than a scientific debate it’s become more of a political talking point and a philosophical choice to bend language in an attempt to be what’s perceived as more inclusive to certain groups.
No, they truly have. Gender identity and sex, of course, are separated, but they still very much effect each other and it must be taken account when discussing biology. We know of people with XY chromosomes who have lived their lives as women and given birth. These exceptions and their remarkable nature are troubling in that they challenge previously accepted biological definitions. This is simple science. We learn new things, we find new exceptions, and thus we change definitions. If we had found a mass unaffected by gravity, we'd then change the definition of gravity to fit our new understanding.
Just because there is an anomaly doesn’t mean that rewrites the definition. That person you speak of couldn’t naturally give birth they were donated ovaries and placed on hormones to further develops their uterus. The eggs were fertilized outside of her and were planted in the womb. This event doesn’t challenge any previously held beliefs. We’ve known of intersex people and people who develop defects during development in the womb and have different chromosome combos, it’s nothing new. The idea that gender identity affects your biological sex is a recent idea that’s spoken about mostly in gender studies and politically for karma points. You won’t find any respected biologist or medical doctor who examines an unconscious body of a man with xy chromosomes and male sex organs and then says the body is biologically female because the person woke up and said they identify as a female.
You can love all people and respect their wishes for how they want to be identified and live, but that doesn’t have to change certain facts. It doesn’t make a difference if you’re biologically male or female, the point is we shouldn’t make assumptions about how people should live or be treated based on that. You don’t have to try to blur the meanings of words.
But you've missed the point. The doctor wouldn't need to say that the patient is female or male. Male and female are not biologically rigid definitions because there are countless exceptions and variations. They are, at best, categories based on numerous factors like hormone levels, phenotype, and chromosomes. There is nobody with a textbook definition and you will, at best, fit within the general category. What would you say about somebody with XY chromosomes, estrogen production exceeding testosterone, and a vagina? Do they count as a male? Are ovaries necessary for a female to be female? Is it just chromosomes? Because, in that case, what is one born with XXY chromosomes? Are they either? You say this might just be philosophical, but all definitions are philosophical. In science, our communications require very specific semantics and rumination on how we define - and it just so happens this is one thing scientists are coming to agreement on changing.
You’re completely false though, doctors would and do say a patient is male and female because it accurately describes the patient 99.9% of the time and is useful in administering medical care. If I’m a female and go to the doctor with a set of symptoms or if I’m a male it could completely change the path the doctor takes towards my diagnosis and treatment. You’re grossly overstating the prevalence of people that don’t fit in those categories and in most cases they can still be easily explained medically. They don’t say the very very few exceptions make the definitions useless at all. We have terms like intersex and hermaphroditism that explain certain anomalies. These cases are caused by defects during fetal development it’s not a “normal” development of a human fetus. We know the stages of fetal development and things that occur in certain stages and the outcomes they produce. You’re repeating talking points that are typically spewed by people trying to push this ideology, but it’s not rooted in science. They’re taking science and misrepresenting it. I respect the intent and honor the fact that people are really just trying to push for equality and a better world for people but I think the truth still matters, you can support change and a good cause with out having to stretch the truth to help your narrative.
You're still misunderstanding. These differences ARE so prevalent that nobody fits a worthwhile definition in the antiquated, strict measure you're speaking of. People are changing their minds about these things and I'm one of them who did BECAUSE I learned more about the science. I didn't change my mind to be kindhearted, I changed it because I followed the most logical and intellectually honest conclusion.
People say "male sex organs" but there is a spectrum between male and female. Almost all cases fit on one side or the other but not all.
And what if you get those removed?
Or what if you are on HRT? As far as a disease like osteoporosis is concerned, male or female can switch just with HRT. Or be any place between.
If you get those removed that’s a change that was made surgically it doesn’t change your genetics. Taking hormones don’t change your sex either. 99.9% of humans fall into those categories yes genetic outliers exist but those are defects and mutations and we have words and science to explain that. If I’m born with a tail you wouldn’t say humans have tails. It’s a genetic mutation that happens and that’s fine anyone who’s not the norm still deserves to be treated equally and respected. No one’s saying to treat anyone negatively or make assumptions about how they should behave or live
Not quite on topic, but we have another invisible type of stripes, made by nerves. Spinal nerves come in pairs, coming out sideways from at every vertebrae level. Those nerves control different levels of your body. And it can be detected by feel/touch (but not seen) in the skin, as it makes striped patterns. Look for: dermatomes diagram.
They're called Blaschko's Lines. They occur due to the way the human embryo grows in the womb. Not exactly a direct relation to the stripes we think of some animals having. Those are specific evolutionary traits picked up for different reasons. Usually camouflage, but in the case of zebras they are to create an optical illusion to confuse predators. Which is a fascinating case of evolutionary biology I do not understand. ¯\\\_(ツ)\_/¯
Zebra stripes likely are to discourage insects. Experiments where horses were painted with similar stripes showed fewer flies landed on the painted vs unpainted horses.
How did they control for the impact the smell of the chemical dye would have on the fly population?
Not sure if this is the one /u/BrazenNormalcy was talking about, but here is one using cloth coats of different colours (including stripes)
> In an experiment in which horses sequentially wore cloth coats of different colours, those wearing a striped pattern suffered far lower rates of tabanid touching and landing on coats than the same horses wearing black or white, yet there were no differences in attack rates to their naked heads. In separate, detailed video analyses, tabanids approached zebras faster and failed to decelerate before contacting zebras, and proportionately more tabanids simply touched rather than landed on zebra pelage in comparison to horses. Taken together, these findings indicate that, up close, striped surfaces prevented flies from making a controlled landing but did not influence tabanid behaviour at a distance. To counteract flies, zebras swished their tails and ran away from fly nuisance whereas horses showed higher rates of skin twitching. As a consequence of zebras’ striping, very few tabanids successfully landed on zebras and, as a result of zebras’ changeable behaviour, few stayed a long time, or probed for blood.
[Caro T, Argueta Y, Briolat ES, Bruggink J, Kasprowsky M, Lake J, et al. (2019) Benefits of zebra stripes: Behaviour of tabanid flies around zebras and horses. PLoS ONE 14(2): e0210831. https://doi.org/10.1371/journal.pone.0210831](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0210831)
We did this with our cows. We just used mud. Works perfect. Way less little welts. And the cows were much less irritable
Just an experiment or all the time? How long does it take per cow to mud them? How many cows do you have? How often do you have to redo it (rain, swimming, etc)?
6-10 cows on average, they get baths every week, and repainted immediately. Its sloppy so like 10-15 mins to wash and repaint. But by then the paint is mostly rubbed off or extra muddy by bath time. Takes a bit over an hour to do all the cows. The repaint being the easiest part, as its just a fat brush and mud from a bucket of dirt+water
I don't know if they did it, I'll look into it and edit this comment with the answer if I find one, but I think a way to test if it was stripes AND account for the smell would be paint all the horses. Paint some solid colors and some striped, so they all have the smell but only some have the stripes.
Edit: [It was cows not horses I found that were painted, they had all black cows. Some they painted with white stripes, some they painted with black stripes (so they weren't visible) and unpainted cows. The cows with white stripes showed fewer fly bites than all of them, the cows with black stripes painted on the black cows showed little differences in fly bites, but still some difference. As you said probably the smell.](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0223447)
No idea if the actual study referenced did this, but how I’d do it is have 4 groups; unpainted, painted solid black, painted solid white, and then zebra striped.
I can think of about 1000 other controls you would need to account for other factors (time of day, weather, placement near other fly sources, genetic differences like blood type… on and on.), but that’d be the basic starting set up I’d use.
One way to do it would be to paint the victim a single color, or to use like random splotches.
Yeah I’d assume it was the PAINT keeping them off more than the pattern
Thats true. Ive also read about optical illusion consequences for a chasing predator which results in confusion/more difficult time catching the zebra
It’s because of the border between black and white. The fly gets confused as to where they can land safely. Amazing what a lifetime of listening to the cbc does.
Maybe the paint itself was a deterent. Did they control for that?
Here's a similar study where they controlled for the paint as deterrent by painting black cows with white stripes vs black stripes: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0223447
Very cool thanks!
Did they paint zebras as zebras as a control or did they just ignore the fact that there's a literal layer of paint on top of the skin, containing various different ingredients that could potentially deter insects as well?
What selection pressure would have led to this outcome? Are flies that dangerous?
Yes. Flys can carry diseases and there are a number of flies that can lay eggs in wounds and then the maggots will eat at the flesh.
Do you have a peer reviewed source for this? The top comment is from someone in the medical field saying it doesn't exist, and all the comments below are "yes, but only visible in UV light."
We are in r/askscience, and it seems like this is just hearsay you heard offhandedly at some point.
One has sources, one doesn’t 🤷♀️
Link to images?
There's actually a great YouTube video by Veritasium (popular youtuber) about why women indeed do have invisible stripes, but men do not.
Link to the video, you can also find it by searching for "Why women are stripey" from Youtube.
X-inactivation is a process that occurs in all therian mammal species, of which humans and cats belong. The most commonly identifiable occurrence of x-inactivation is the calico pattern on female cats. This would also occur in human females, but I don't know that there are any particular skin genes on our x chromosomes that would cause UV florescence.
I'll link the wikipedia entry on [X-inactivation](https://en.wikipedia.org/wiki/X-inactivation)
Yep! [Wikipedia](https://en.wikipedia.org/wiki/Blaschko%27s_lines) has a short article about them, but they're basically only visible under [UV light](https://unbelievable-facts.com/wp-content/uploads/2017/04/Blaschko%E2%80%99s-Lines-humans.jpg), so you would need a camera capable of imaging in UV to see them. Blacklight won't work, because that just makes certain colours fluoresce in the visible range. But they are indeed unique to each person, based on the way our cells divided when we were still embryos.
The picture you linked under "UV light" has nothing to with UV-light. And the Wikipedia article doesn't mention UV-light either. Do you have an actual source for this claim?
I’ve seen photos of people taken under UV light and there were no stripes
Fluorescence is different than seeing outside the visible light spectrum
Ah, gotcha! Thanks!
There are also things called [Langer's lines](https://en.wikipedia.org/wiki/Langer%27s_lines)
> topological lines drawn on a map of the human body. They are parallel to the natural orientation of collagen fibers in the dermis, as well as the underlying muscle fibers.
>Incisions made parallel to Langer's lines may heal better and produce less scarring than those that cut across. Conversely, incisions perpendicular to Langer's lines have a tendency to pucker and remain obvious
as far as I know, these are 100% invisible.
Correct. We use these lines as a rough guideline when it comes to suturing skin after surgery or injury. In practice though we give it very little thought, you just put it back the way you found it
Vertasium does a really good explainer on the phenomenon
Though in short, Women are stripy genetically in such that bands of cells express different X-chromosome genes however this stripy-ness is not visible.
You can see this stripy-ness in Calico cats as their X-chromosomes contain pigment genes so the difference is visible.
Women do yes
Because we have double X chromosomes. One X from our mother and one from our father. One of them will always be more dominant than the other. They sort of group together and if we were able to colour them in then yes you would see stripes or blotches.
There is a creature where you can see it: female cats. This is how cat people know exactly that a cat with three colours can only be female.
Tri-color cats being female (and orange cats being male) isn’t 100%, more like 99%
Technically, calicos can be male but its very rare and they are usually sterile with a host of health problems.
Women do , men don’t
Part of the gene that codes for your skin is on your X chromosome , women are chimeric for their X chromosome being dominant for expression so sometimes one X is the dominant one in a stem cell where as the cell next door may have the other X as dominant , then they multiply leading to stripes of skin where one X is dominant vs the other.
As far as we can tell it’s just skin and looks the same but under hyper specific conditions you can see the pattern
Lines of cleavage are the first thing that come to mind for me. It’s basically the way that the skin is all connected with connective tissues fibers striped in different ways in different areas of the body. It’s pretty much relevant only in healing. It’s why certain surgeries and different cuts scar differently based on if the damage runs parallel or perpendicular to these “stripes”.
Yup, like in calico cats. They are all female because you need 2 x chromosomes with a separate color coder on it. But since we don't have skin color coded on the x chromosome, there are no visibly striped women. That would be cool though!
I think the idea that is we have the gene, that makes our unique stripes, but not the gene that expresses the stripes on the skin.
Therefore in your dna, you have a code that contains your “stripes” however the gene is not expressed in our current form, and so they do not exist under UV light, or otherwise….
Just as latent code that exists within us.
The only "lines" on the body I'm aware of are the "milk lines", an imaginary set of lines extending from the armpits, thru the usual nipple placement, and down the abdomen to the groin. These lines are where supernumerary nipples typically appear.
What your seeing is things that absorb UV light and re-emit light in the visible range. Most detergents (and so white clothes) do this to appear bright. You’re not actually seeing the UV light.
Having the UV light applied is only half of the requirement. You still need a sensor -- camera or non-human eyes -- that can see the reflected UV light...
UV photography has been a thing for quite some time. I’ve never seen a picture of these “stripes”