▲ 166 points
back
101 comments
The 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.
Amazing. I didn't know that. Prostate in Greek means Protector and took its name from it's role. Ages ago this function was known.
> 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?
There'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.
>Given its vast complexity, and the timeline of its creation/evolution
I will just say, the human body in particular has only been around for a vanishingly short period of time in evolutionary terms. A lot of the quirks and arguable flaws identified in this piece (painful childbirth through the pelvis, back pain) and others (varicoceles in the left internal spermatic vein, hernias, other pelvic floor disorders) can be attributed to our very recent move to full bipedalism.
If we’re talking about features we share with other mammals or even other primates, sure, they’ve probably stood the test of time for a reason. But for features that have only really been in existence for a couple million years, those I don’t think we should treat with the same kind of reverence.
> 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.
Hasn't it been settled for a while that they're part of the immune system? Wiki is clear [0] on the subject; they're there to repel bacteria. They're quite important and removing them, unless there is no other choice, seems like a terrible idea.
> Who would let a junior dev trim bits, or boldly modify a decades old codebase?
"Chesterton's Fence": you shouldn't tear down a fence (or a piece of code) until you understand exactly why it was put there in the first place.
Reminds me of Chesterton's fence [1]:
"In the matter of reforming things, as distinct from deforming them, there is one plain and simple principle; a principle which will probably be called a paradox. There exists in such a case a certain institution or law; let us say, for the sake of simplicity, a fence or gate erected across a road. The more modern type of reformer goes gaily up to it and says, "I don't see the use of this; let us clear it away." To which the more intelligent type of reformer will do well to answer: "If you don't see the use of it, I certainly won't let you clear it away. Go away and think. Then, when you can come back and tell me that you do see the use of it, I may allow you to destroy it.""
My doctor has (with case by case exceptions as needed) a general rule to encourage a conservative approach: if at all possible, attempt to leave with everything you arrived with
Just like clergymen used to omit "we believe x, y, or z" when making some mystical claims, "scientists" of today omit "as far as we know from their communication with the layman...
>Who would let a junior dev trim bits, or boldly modify a decades old codebase?
Ones who does not understand the idea of the "Chesterson's Fence"
I narrowly avoided tonsil removal as a child and I'm glad I did, it sounds like the science rotated around to them having a rather important immune function after all.
I suspect the next round of backpedalling will be around the current wisdom teeth removal fad.
similar story with the appendix.
Initially considered a useless vestige, now thought to be involved with maintaining gut bacteria.
Let me defend ear twitching. It's a subtle way of communication for those of us so blessed with the ability.
Not 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.
Came 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.
Part 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.
I 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.
It also reads like a collection of evidence against intelligent design.
There 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.
Male babies can lactate due to the high concentration of hormones in mother's milk.
seems to be heavily affected by hormones as many trans women end up experiencing some level of lactation while undergoing hormone replacement therapy.
This 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 ...
Ah; 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?
Yes, 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)
> 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/liVQo...
Cesarean childbirth and psychosocial outcomes: A meta-analysis. (1996) https://psycnet.apa.org/record/1996-05270-009
I'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.
The eyes of squids are right side out, unlike ours. I wonder what other animals have the "correct" version of these features.
Full-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_o...
What if they're stupider because of it?
What about testicles outside the body? Every man has a painful story why it’s not a good idea..
I 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...
It 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.
You’ve probed Chesterton’s Fence; now let’s turn the page to Chesterton’s Appendix!
>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.
The 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/
Fun and educating article. Reading that we once had three eyes, lead me to this paper: 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?
Anatomy 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.
How about feeling the hand even after amputation. What do you think, why is it so?
This 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.
I hear that visual cortex being on the rear of the brain when the eyes are on the front is another example.
I assume the intelligent designer was fired for this.
I didn’t think about it this way, makes sense.
>The common crowding of human teeth—especially "wisdom" teeth, which erupt last
>is traceable to the evolutionary shortening of our jaw.
Complete baloney.