5 ms·
Axial twist theory
- ahartmetz 1y agoThe schematic illustrations are just adorable! Whoever did these, fantastic job.
- qgin 1y agoJust look at this distinguished gentleman https://upload.wikimedia.org/wikipedia/commons/thumb/6/61/FigOppositeAsymmetry.pdf/page1-260px-FigOppositeAsymmetry.pdf.jpg https://upload.wikimedia.org/wikipedia/commons/thumb/6/61/Fi...
- bongodongobob 1y agoIt looks like brainrot material, I love it. This has some meme potential.
- frozenseven 1y agoNot gonna lie, those illustrations are a bit scary. Which makes it even better.
- comex 1y agoI found the illustrations confusing; I had to go over them and the accompanying text over and over before I understood what was being depicted.
- DC-3 1y agoNot saying the theory is bunk but I think that basically everything about this on Wikipedia is written and illustrated by the researcher who devised the theory. So it's that guy.
- ahartmetz 1y agoI doubt it because the guy died in 1934. There is no short, clear statement on the Wikipedia page that it was this guy, only that he "proposed a theory". https://en.wikipedia.org/wiki/Santiago_Ram%C3%B3n_y_Cajal https://en.wikipedia.org/wiki/Santiago_Ram%C3%B3n_y_Cajal
- pitpatagain 1y agoThat's the proposer of visual map-based theory, a different explanation for the same things axial twist theory tries to explain. Axial twist is much more recent.
- esafak 1y agohttps://en.wikipedia.org/wiki/User:Marci68 https://en.wikipedia.org/wiki/User:Marci68
- riffic 1y agosurgeon Francisco Torrent-Guasp determined the human heart to be continuous, helical muscular structure like a conch shell. maybe I've been the holofractal subreddit a bit too long because folks really seem to have a thing for the twisty toroidal vortexes there.
- taneq 1y agoInteresting! My pet theory about the crossover in the optic nerve is that it's the simplest way to get goal-seeking behaviour. Proto-eye activates, activates muscles on opposite side of body, organism turns towards activated proto-eye. Fun speculation: Maybe we started with no crossover (which gives avoidance behaviour, keeping the organism free-swimming). This still works for a while as the axial angle between eyes and muscle groups increases, so there's no real penalty for having a bit of a twist. As the twist increases, it starts acting a bit like a discriminator, where we avoid small things less than large things, which seems good if we want to eat small things. Past 90°, we start spiraling towards things instead of away from them, which admittedly makes us crash into large things more, but we can chase moving things. Hunting has evolved!
- admin_account 1y agoThat’s interesting! My mind always just assumes the reason is some “core” biological reason. I think contralateral wiring helps the brain manage signal sequencing while preserving evolutionary symmetry. The spinal cord handles rapid reflexes (pulling away from a hot stove), leaving the brain for slower non-immediate tasks. By crossing nerves before they reach the brain a standardized delay is introduced, giving the brain a predictable offset to filter against. The optic chiasm follows the same logic. And I think this is necessary to keep same-side brain-body pairs from over-optimizing (direct nerve connection from the right hand to the right brain hemisphere) their paths at the expense of balance, preserving biological symmetry.
- polishdude20 1y agoIve always wondered if it had something to do with up being the direction of the sun and light and down being the direction of gravity, depth, darkness.
- Sharlin 1y agoInvertebrates seem to have had no problems evolving hunting even though they don’t have a twisted body plan. And hunting almost certainly evolved before this change occurred in the vertebrate lineage.
- OhMeadhbh 1y agoWhen I see a seemingly "random" post on HN I always wonder if someone happened across some random bit of info and thought it so interesting they just had to share, or if there's some other bit of related news I haven't heard about. Did we just discover space starfish on Mars? I'm guessing I would have heard about that. Or did someone post a paper challenging axial twist orthodoxy? Guess I can google that. But there's a delightful span between seeing someone post something on HN unrelated to AI, Cryptocurrencies or startups selling VS-Code extensions and the moment when I satisfy myself something outlandish (like space starfish) hasn't happened. During that time, all things are plausible. [Edit. Which is not to say I disparage or discourage posting cool things you've found on the net. That's kind of what many of us are here for.]
- mk_stjames 1y agoOne of the most delightful things involving reading HN is seeing a strange, context-less post in the morning, and then, later in the day or evening, coming across another piece of information- maybe a popular article on another website or a very popular youtube video- that then leads you to some research hole, possibly wikipedia'ing and following the older, linked sources- where you wind up on the exact page linked from the random post that morning and it becomes pretty obvious that you just retraced the exact steps that a like-minded individual had done earlier that day. It's happened to me several times where I doubt it could be simply recency bias coupled with chance of topics, due to the specificity and narrow directed-ness of the graph.
- parpfish 1y agosame. it happens to me all the time on HN. on one hand, i feel like this is a text-book example of the Bader-Meinhoff illusion [0]. but... there's an actual causal mechanism that could drive it. show an interesting article to the HN crowd -> some subset of HN readers are inspired to go down a wikipedia rabbit hole and post some cool thing they found back on HN -> people that saw the original interesting post will not only see the related followup post, but they'll upvote it and cause even MORE to see it [0] https://en.wikipedia.org/wiki/Frequency_illusion https://en.wikipedia.org/wiki/Frequency_illusion
- monkeycantype 1y agocan you be my collective memory for a minute, I remember the existence of a very satisfying engineering explanation for why the representation of various body parts needs to be flipped left/right in the brain that came down to the topology of the wiring, and explained why unflipped isn't feasible / or perhaps it was just less efficient, it was one of those 'mind explodes' moments, but now I can't recall the logic.
- bongodongobob 1y agoI always thought it was so if an organism takes head damage on one side, the limbs facing the danger will have a better chance to still work, giving it a better chance to fend whatever off and survive.
- topaz0 1y agoThat has the smell of an evolutionary just so story
- monkeycantype 1y agono there is a very specific reason, related to mapping the 2d surface of your body to a 2d mapping on your brain that allows the areas of your brain that process sensory input from your skin to be adjacent to the processing of the areas that are adjacent on the skin that only works with a flip, I can remember what that is, I only remember the tingle of understanding it at the time
- jacobsimon 1y agoCurious, let me know if you find anything about it! That does sort of explain why the brain areas would be locally flipped, but maybe doesn’t explain the global flip (right body -> left brain) that the original article is talking about.
- monkeycantype 1y agoI think it's the theory in the article linked just above by renewiltord
- adrian_b 1y agoThere is no doubt that the body of the vertebrates posterior to the head is rotated in comparison with that of most animals, so that what is up in other animals is down in vertebrates and vice-versa. Evidence for this has been known and it has continued to accumulate for about two centuries. Where there is uncertainty is about what has happened to the head. According to the supposition presented in the linked article, most of the head has preserved the same orientation as in most other animals, either because it never took part in the rotation of the rest of the body, or because later it has made an additional half-turn rotation, which has brought it back to the initial orientation. Among these 2 alternatives, I think that the first is more plausible, because in that case the environment would have retained a constant orientation with respect to the principal senses, even if the posterior body rotated. While this theory supposes that most of the head of the vertebrates has the original orientation, also all competing theories must accept that at least a few parts of the head either have never participated to the body rotation, or a subsequent rotation has brought them back in the original position, e.g. the mouth.
- qoez 1y agoI feel like these whimsy diagrams will eventually be taken down or replaced with something more formal and corporate. That's a shame imo. I wish there was a place for a wiki style community edited resource that allowed more whimsy.
- Razengan 1y agoCan someone TL;DR? What does this mean? It just made me think, whether it's related or not, shouldn't the "natural" resting position of human heads be "upwards" like the rest of the animal world? I mean if you consider the worm/fish template, it's o---> where "o" is the "tail end" and ">" is the head. It points in the "direction" of the body. All other mammals and birds are also o---> | | whereas we weirdos are o—--v
- Sharlin 1y agoNo. We’re talking about axial twist that occurred very early in vertebrate evolution. The hypothesis aims to explain why each brain hemisphere is associated with the opposite side of the body, including the eyes, in vertebrates (but not in invertebrates).
- samirillian 1y agoIs it possible that lefties twisted in the opposite direction