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Quirks of Human Anatomy
- ginko 6mo agoNot humans specifically but one of my favorite quirks of vertebrate evolution is the recurrent laryngeal nerve that loops around the aorta and goes back up to the larynx[1]. In giraffes that nerve is several meters long. [1] https://en.wikipedia.org/wiki/Recurrent_laryngeal_nerve https://en.wikipedia.org/wiki/Recurrent_laryngeal_nerve
- rasse 6mo agoCame here to say just this. Another interesting one is the auricular tubercle[1], where the genetic trait of a "pointy" ear found in other mammals reappears in some humans. [1] https://en.wikipedia.org/wiki/Darwin%27s_tubercle https://en.wikipedia.org/wiki/Darwin%27s_tubercle
- krzat 6mo agoCool, maybe we could make CRISPR elves?
- tempaccountabcd 6mo ago[dead]
- snthpy 6mo agoThis is how future codebases will be analysed. Don't let perfect be the enemy of good. Evolution been doing Agile for aeons. Responding to change over following a plan ...
- 9dev 6mo agoAh; but how annoying it is to discover something like the inverted retina bug, only to figure out it is effectively unsolvable now due to all the follow-up architecture decisions built on it?
- ziml77 6mo agoYes, don't give a crap about doing it right so all your costs instead move into support and maintenance (which in this analogy is healthcare)
- ButlerianJihad 6mo agoYou’ve probed Chesterton’s Fence; now let’s turn the page to Chesterton’s Appendix!
- ivanb 6mo agoIt would be nice to refactor some of these. Vas deferens and laryngeal nerve look like easy pickings. Leave me my ear-wiggling. Any last bit of expression matters. I'm dreading the horror of genetic manipulation it would open. The gene editing craze feels like it is right around the corner.
- volemo 6mo agoI cannot wait for the second pair of arms. :D
- hermitcrab 6mo agoit has been suggested that a human genetically-engineered for a life in zero G would be better of with no legs and extra arms.
- raincole 6mo agoThe eyes of squids are right side out, unlike ours. I wonder what other animals have the "correct" version of these features.
- Cockbrand 6mo agoFull-featured eyes have developed a few times independently [0], so it could be that mammals and squids have evolved on different branches that split before the common ancestors had eyes as a feature. [0] https://en.wikipedia.org/wiki/Evolution_of_the_eye#Origins_of_the_eye https://en.wikipedia.org/wiki/Evolution_of_the_eye#Origins_o...
- backscratches 6mo agoIsn't that exclusively what that indicates?
- ButlerianJihad 6mo agohttps://en.wikipedia.org/wiki/Tuatara#Parietal_eye_(third_eye) https://en.wikipedia.org/wiki/Tuatara#Parietal_eye_(third_ey...
- fgfarben 6mo agoWhat if they're stupider because of it?
- josefrichter 6mo agoWhat about testicles outside the body? Every man has a painful story why it’s not a good idea..
- xg15 6mo agoI read this does have a functional reason: Sperm cells have to be kept at slightly lower temperature than the body temperature, so if the testicles were inside the body, the sperm wouldn't survive. Of course you could ask why sperm is so temperature sensitive in the first place...
- volemo 6mo agoIf elephants did it, I’m sure we can too.
- beAbU 6mo agoWe did do it! It's called testicles!
- volemo 6mo agoBut ours are outside. :(
- melagonster 6mo agoThey have a complex system to mantain the specific temperature. Huaman and other smaller animal do not have enough space to it inside.
- polotics 6mo agoIf we were as large as elephants, then yes.
- fastjack42 6mo agoNow that sounds like a design flaw in sperm cells
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- xg15 6mo ago>The hole in the retina is sizeable (~9 full moons in the sky), but we don’t notice it because [...] (2) our brain automatically fills in gaps in our visual field by interpolation I still remember this bit from school and various pop-sci book, but is it actually true? Is there really some group of neurons in the brain somewhere that actively tries to restore the "raw" visual information that was blocked by the blind spot? Thinking of ANNs, I felt it was more realistic that higher layers in the visual cortex are mostly only using the visual information to find patterns anyway, and that they're robust enough they can still find those patterns without the data from the blind spot locations. (As long as a pattern isn't fully contained within the blind spot regions of course) An analogy would be a QR code reader that can still parse the encoded information if a part of the QR code is missing - but it won't actually "reconstruct" the missing sections to do this. But I don't know if it really works like this.
- glenstein 6mo ago>(As long as a pattern isn't fully contained within the blind spot regions of course) There are dedicated optical illusion/explainers that give you the experience of the brain patching over the space with neutral background, even if there's something there, like a symbol or a star. So if it's something featureless or continuous, like a wall of your room that's a solid color, or a sheet of college ruled paper, the pattern can just be continued. That said I would stress there's limits to how much of that you can do just by pattern extrapolation as opposed to deriving images from distinct and specific information in a given region of the visual field. You have to know enough about a stretch of visual space to know that it's appropriate to spread a pattern over it, and that's the thing the blind spot doesn't know.
- ahalay-mahalay 6mo agoWhat’s interesting about that is that brain doesn’t actually give you much access to the sensor information directly, but gives an interpretation instead. There is a thing called Saccadic Suppression that blocks visual data processing for 50ms when eyes are moving, and the brain just backfills that missing data from the “next frame”. https://en.wikipedia.org/wiki/Saccadic_masking https://en.wikipedia.org/wiki/Saccadic_masking
- mbivert 6mo ago> f. Nipples are useless in human males (cf. Ch. 5). When I was a kid, I got my tonsils removed "because they were useless and a source of illness". I've recently heard that tonsil removal is now more disputed: it may collect filth, sure, but it may also prevent it from going deeper into the body, which may cause more serious illnesses. Given its vast complexity, and the timeline of its creation/evolution, I remain skeptical over bold claims about the human body. It's really missing an "as far as we know." The ability to go beyond what is known is paramount to the progress of science, and historically attested with some intensity (e.g. Earth's shape, relativity with time/space & axiomatic geometry). Humility thus feels like a better posture. Who would let a junior dev trim bits, or boldly modify a decades old codebase?
- joefourier 6mo agoThere's also a difference between having no immediate use, and having no reason to exist. From what I understand, sexual differentiation works by having the Y chromosome act as a switch, and both sexes have to share the same blueprint with hormones guided the development of their organs. For males not to have nipples, they'd need to be actively destroyed, which poses a risk for females to also not have nipples, which is much worse than males having harmless, inactive nipples.
- Polizeiposaune 6mo agoThe actual switch (in humans and I believe most mammals) is a gene called SRY. The Y chromosome is just the (usual) container for the switch.
- canjobear 6mo agoIt doesn't seem like eliminating nipples should be any harder than eliminating the uterus...
- numpad0 6mo agomale and female sexual organs are the same thing inside out of each others, to some extent.
- ajitesh13 6mo agoHow about feeling the hand even after amputation. What do you think, why is it so?
- pestatije 6mo agoits part of the learning process...the model still keeps the hand present
- ajb 6mo agoThere are occasional cases of male lactation reported in humans. Very rare though. In the guinea pig, the large head at birth is provided for by the carteliginous symphysis joint in the hips detaching. However unless the animal gives birth early enough (which always happens in the wild), they lose this capability and die if impregnated later. Some doctors thought it a good idea to try to emulate this in humans by cutting the cartilage there instead of doing a cesarian section, but this causes permanent problems, as in humans the joint does not reattach. Notoriously, for religious reasons some doctors decided to do so anyway, since cesarian section reduces the number of pregnancies a woman can have, which they regarded as more important than being able to walk easily and being continent.
- goodmythical 6mo agoseems to be heavily affected by hormones as many trans women end up experiencing some level of lactation while undergoing hormone replacement therapy.
- SomeHacker44 6mo agoMale babies can lactate due to the high concentration of hormones in mother's milk.
- odyssey7 6mo agoPart of this reads like a shortlist of things that doctors and scientists don’t know enough about yet. If you’re looking for a PhD topic, here are some ideas.
- amelius 6mo agoIt also reads like a collection of evidence against intelligent design.
- drfloyd51 6mo agoAkshully… These flaws were left in so there would be no proof of a creator. Because with proof, there is no faith. And faith is a requirement of winning. Imagine how hard it must have been to design “flaws” like these but still allow humans to survive. I can’t. Therefore, you can’t. Only an omnipotent god could do it. Checkmate atheists!
- deleted 6mo ago[deleted]
- hn_throwaway_99 6mo agoI strongly disagree. Literally every item in there makes perfect sense if you have an understanding of how evolution works. E.g. many of these items are simply vestigial in some sense, where their presence doesn't actively harm the species and it doesn't impose any substantial energy budget. E.g. the current top comment here is about male nipples. Male nipples may be "useless", but they're not actively harmful (and they can certainly be pleasurable during sex), so there is no evolutionary pressure to get rid of them. The perineal raphe (i.e. the "male taint stitch") also has no purpose but is simply a byproduct of how the male forms in utero. As the article points out, most of the other "quirks" are simply what evolution had to deal with. You may say the eye is "weird" because the photoreceptors lie behind the ganglion cells, but it certainly works quite well, generally. And it doesn't "have to" be this way. Octopus eyes are completely the opposite and a great example of convergent evolution. Other examples are simply tradeoffs. There is pretty obvious survival advantage for humans having a large brain, but this then adds complexity for how the head gets out of the relatively small pelvic canal. I honestly didn't see any examples in this list that aren't well understood and well explained by scientists. If anything most of these provide excellent examples of how evolution works.
- dennis_jeeves2 6mo ago>The common crowding of human teeth—especially "wisdom" teeth, which erupt last >is traceable to the evolutionary shortening of our jaw. Complete baloney.
- theandrewbailey 6mo agoTeeth are easily lost, so wisdom teeth are nature's backup plan, or so I heard.
- dennis_jeeves2 6mo agoCould be the case. But the explanation of crowded tooth being ascribed to evolution is completely false. If one dug around literature even a teeny bit one realizes that many hunter gather groups even today have a a full set of tooth perfectly aligned in the jaw. Dentists, Weston A. Price about a century back and more recently John and Mike Mew (father/son so the same last name) come to mind who tell a different story from the mainstream evolutionary explanation for crowded tooth.
- davycro 6mo ago[dead]
- danilor 6mo agoThe page claims that babies can suckle and breathe at the same time, but upon first-page-of-google research, it seems not to be true https://pubmed.ncbi.nlm.nih.gov/34636089/ https://pubmed.ncbi.nlm.nih.gov/34636089/
- alok-g 6mo agoI hear that visual cortex being on the rear of the brain when the eyes are on the front is another example.
- cbarnes99 6mo agoThe urethra is routed through the prostate specifically because it needs to occlude it during sex. The prostate swells during an erection to obstruct the urethra and significantly reduce the likelihood of a bacterial infection in the bladder. It's a very important function.
- tsoukase 6mo agoAmazing. I didn't know that. Prostate in Greek means Protector and took its name from it's role. Ages ago this function was known.
- jgalt212 6mo agoYour statement implies the ancient Greeks discovered the functionality and named this organ.
- tsoukase 6mo agoNo, I was wrong. Medical history says that it was discovered in the 16th c and initially was named Parastate, meaning a "helper" gland. Later the name changed by chance to Prostate and stays revevant as it was later found that it's role is also protective.
- tsoukase 6mo agoAnatomy is the latest image snapshot of Evolution. Evolutionary quirks are more general, interesting and important. One is the debated and funny Haeckel’s law: ontogeny recapitulates phylogeny.
- SummSolutions 6mo agoFun and educating article. Reading that we once had three eyes, lead me to this paper: https://www.sciencedirect.com/science/article/pii/S0960982218302938 https://www.sciencedirect.com/science/article/pii/S096098221.... Fascinating that many vertebrates had a third light-sensing organ (called the pineal gland) on top of their heads millions of years ago. If our eyes are now the main mode of light transmission to the pineal gland, should we be wearing sunglasses all of the time?
- doctorzook 6mo agoI assume the intelligent designer was fired for this.
- nwhnwh 6mo agoI assume the writer is a one-dimensional man.
- arcknighttech 6mo ago[dead]
- nwhnwh 6mo agoThis is kind of funny. This is what produces one-dimensional humans. The desire to put it this way... the underlying assumptions like "pain is not good", and so on... is ideological, not scientific.
- erelong 6mo ago[dead]
- 47282847 6mo ago> The process would be safer (and less painful) if the path mimicked a caesarean section, with the baby exiting through the navel. Prenatal development research posits that natural birth is a required “early training experience” and that a lack or disruption of that collaboration between mother, environment and (already conscious) baby during pregnancy and during birth (like cesarean) may result in various psychological deficiencies/difficulties later in life. See eg. The Emotional Ramifications of Being Born in a Cesarean Delivery (2017) https://birthpsychology.com/wp-content/uploads/2024/09/liVQo7B5-2.pdf https://birthpsychology.com/wp-content/uploads/2024/09/liVQo... Cesarean childbirth and psychosocial outcomes: A meta-analysis. (1996) https://psycnet.apa.org/record/1996-05270-009 https://psycnet.apa.org/record/1996-05270-009
- cogman10 6mo agoI'm sorry, first link is from an organization dedicated to this fringe theory. Second link is pretty dated and I wonder if more recent studies back this finding.
- 47282847 6mo agoChen, H., & Tan, D. (2019). Cesarean section or natural childbirth? Cesarean birth may damage your health. Frontiers in Psychology, 10, Article 351. https://doi.org/10.3389/fpsyg.2019.00351 https://doi.org/10.3389/fpsyg.2019.00351 Orovou, E., Antoniou, E., Zervas, I., & Sarantaki, A. (2025). Prevalence and correlates of postpartum PTSD following emergency cesarean sections: Implications for perinatal mental health care: A systematic review and meta-analysis. BMC Psychology, 13, Article 26. https://doi.org/10.1186/s40359-025-02344-5 https://doi.org/10.1186/s40359-025-02344-5 Shen, X.-Y., Wang, J., Zhang, W.-N., Zhao, M., Ju, J., Li, X.-Y., Lu, Q., Wang, B., & Zou, L.-P. (2021). Cesarean section due to social factors affects children’s psychology and behavior: A retrospective cohort study. Frontiers in Pediatrics, 8, Article 586957. https://doi.org/10.3389/fped.2020.586957 https://doi.org/10.3389/fped.2020.586957 Hemminki, E. (1991). Long term maternal health effects of caesarean section. Journal of Epidemiology & Community Health, 45(1), 24–28. https://doi.org/10.1136/jech.45.1.24 https://doi.org/10.1136/jech.45.1.24 Handbook of Prenatal and Perinatal Psychology: Integrating Research and Practice Editors: Klaus Evertz, Ludwig Janus, Rupert Linder https://doi.org/10.1007/978-3-030-41716-1 https://doi.org/10.1007/978-3-030-41716-1 Publisher Springer Cham 2020
- Pixelora 6mo agoI didn’t think about it this way, makes sense.
- jocelyner 6mo ago[flagged]