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Life’s preference for symmetry is like ‘a new law of nature’
- stardenburden 5y agohttps://archive.is/CVYlp https://archive.is/CVYlp
- jw1224 5y agoThe universe appears to be fractal-like in nature, so I would speculate these biological symmetries are a reflection of the symmetries we find in the laws of physics, too. ScienceClic is an extremely underrated YouTube channel producing incredible visualisations for scientific theories. They manage to cover some very advanced concepts, in an easily accessible way. Their video on "The Symmetries of the Universe" was eye-opening, and somewhat mindblowing in the context of the bigger picture: https://www.youtube.com/watch?v=hF_uHfSoOGA& https://www.youtube.com/watch?v=hF_uHfSoOGA&
- wrnr 5y agoNature uses symmetrie when it is useful, but if it isn't it doesn't. Many such examples, L-sucrose vs R-sucrose, male-female differences. The same in physics and mathematics, Higgs mechanism is dependent on symmetry breaking of the weak force, and in mathematics the very nature of symmetry (group theory) has all sort of random exceptions of the pariah group of the sporadic simple groups.
- jazzyjackson 5y agoPersonally I consider any "random" abberations to be symptoms of the hairy dog theorom: you cant comb all the hair to lie flat, somewhere on the spherical dog, you're going to get a cowlick, it is unavoidable in the meantime, chirality is simply mirror symmetry : curious part to me, is how mirror symmetry works out as one half being the "inside out" version of the other, turn a left handed glove inside out and it will fit the right hand. Maybe points to 4th dimensional stuffs, I never could grok how to turn a sphere inside out without pinching
- kragen 5y agothe technical name is 'the hairy ball theorem'
- ykonstant 5y agoHere are two classic youtube videos on the topic of sphere eversion; they mostly overlap, but I am posting both for double the hilarity in the comment sections :) (the full 21 minute one) https://www.youtube.com/watch?v=wO61D9x6lNY https://www.youtube.com/watch?v=wO61D9x6lNY (the first 10 minutes) https://www.youtube.com/watch?v=sKqt6e7EcCs https://www.youtube.com/watch?v=sKqt6e7EcCs If I remember correctly, I think the 10 minute one has the more hilarious comment section.
- DennisP 5y agoThe article kinda says the opposite: that even when symmetry gives the organism no particular advantage, it still tends to get used because it's easier to code in the DNA. That doesn't mean there will be no counterexamples ever. Sometimes asymmetry gives an advantage so it's worth the extra coding.
- kragen 5y agoThis is tautological; it's a slight rewording of "Nature favors symmetry when nature favors symmetry." This can be seen to be true without knowing anything about nature or symmetry, so it's a singularly unilluminating proposition about either. From my point of view, the interesting question is this: when are those times, and what are the particular properties of nature, or of symmetry, that causes nature to favor symmetry at those times but not others?
- dr_hooo 5y agoGreat channel, thanks for the heads up!
- Barrin92 5y agoI'm surprised that this is characterized as such a novel idea in the article because I'm almost certain I've had this discussion ages ago on HN here. I think it was someone asking "why the hell are there spirals everywhere" and multiple people pretty quickly pointed out that self-repeating, symmetric, and fractal patterns are simply a very easy, 'low-information' ways to build larger structures.
- zitterbewegung 5y agoA preprint of the information that was derived to make the above article has been available for a year. https://www.biorxiv.org/content/10.1101/2021.07.28.454038v2 https://www.biorxiv.org/content/10.1101/2021.07.28.454038v2
- jazzyjackson 5y agoa mind-rewiring video by numberphile concerning the golden ratio [0] made sense of all the spiral overlay art: yes, plants use it because it is an optimal solution for minimizing overlap when sprouting leaves during growth, maximizing spatial coverage but also, as a number that is least able to be approximated by rational, erm, ratios - it is a pattern that most closely approximates random patterns. So more than any other spiral, a fibonacci spiral has the highest likelihood of overlapping random points in 2D space... (and fibonacci series converges on the golden ratio because they are equivelent expressions of the continued fraction 1+(1/(1+(1/(1+(1/(1+(1/... [0] https://youtu.be/sj8Sg8qnjOg https://youtu.be/sj8Sg8qnjOg
- thaumasiotes 5y ago> and fibonacci series converges on the golden ratio because they are equivelent expressions of the continued fraction 1+(1/(1+(1/(1+(1/(1+(1/... Just for fun, note that those numerators and denominators reflect the coefficients (1 and 1) in the Fibonacci recurrence equation F_n = 1*F_{n-1} + 1*F_{n-2}.[1] Any sequence obeying this equation will converge to the same ratio between adjacent terms. But the Fibonacci series is "perfect" in that it bottoms out at 1 and 1, never interrupting the pattern even after an infinite number of terms have gone by. In contrast, if you defined a similar series starting at 3 and 4, that series would converge to the continued fraction 1/(1+1/(1+1/1+(1/ ... 1+(3/4) ))), which is exactly equal as long as you can't get across the infinite number of 1s in the expansion of "...". [1] As an example of how this works, if you have the recurrence relation f(k) = 3f(k-1) + 2f(k-2), then the limit of f(n)/f(n-1) as n goes to infinity is the continued fraction 3 + 2/(3 + 2/(3 + 2/(3 + ...
- beefman 5y agoPaper: https://www.pnas.org/doi/full/10.1073/pnas.2113883119 https://www.pnas.org/doi/full/10.1073/pnas.2113883119 Preprint: https://www.biorxiv.org/content/10.1101/2021.07.28.454038v2 https://www.biorxiv.org/content/10.1101/2021.07.28.454038v2
- antattack 5y ago"Why does symmetry reign supreme? Biologists aren’t sure — there’s no reason based in natural selection for symmetry’s prevalence in such varied forms of life and their building blocks." Of course there is a natural selection reason - symmetrical structures are stronger.
- jlawson 5y agoThey're also info-compressed. You can re-use the same DNA for both sides. This means you have less meaningful information to maintain against random mutation pressure over time. Symmetry is also challenging to maintain and very visible; any malformation is obvious. This is useful in showing health and genetic fitness to mates. Many tasks are also inherently symmetrical, like locomotion. Evolving the two legs totally separately would be very error-prone and you'd never quite get it right. Having them both just be copies of the same structure is much cleaner and always efficiently completes the task. Same for things like binocular vision, having ears that hear equally and so can easily echolocate, etc.
- limpingduck 5y ago"Some owls have ears located directly across from each other, in symmetrical placement. Others have asymmetrical placement, where an ear on one side of the head is located above the one on the other side of the head, which increases their ability to locate sound on a vertical axis. These owls use their uneven ears to judge exactly where sound is coming from." https://www.owlresearchinstitute.org/adaptations https://www.owlresearchinstitute.org/adaptations
- jlawson 5y agoInteresting to see the confirmation - Horizontal alignment (symmetry) is best for most animals because they really need to echolocate on the horizontal plane. For the few that don't, some have adapted!
- jameshart 5y ago"symmetrical structures are stronger" - citation needed. Stronger under what condition? For the same amount of material? For the same amount of information needed to describe how to build the structure? Do we see evidence of structures which don't require strength being more likely to evolve to be asymmetric? Or do you just mean 'stronger' in a survival-of-the-fittest sense - symmetrical structures are fitter? It's not at all obvious to me that this should be the case. Indeed, some very strong natural structures like shells are not symmetric at all.
- hcrisp 5y agoThe article mentions the human heart is asymmetrical, which was an exception I thought of immediately. And actually there are many more internal organs that are too (maybe more than are not?), such as: - lungs (the right has 3 lobes, the left only 2) - stomach - pancreas - instestines - gall bladder - liver I once heard of someone that went to the ER for appendicitis and when they imaged him, some of his internal organs were left-right reversed!
- echelon 5y agoI got paywalled, but the title is bogus if you consider biology at the molecular level, where everything is chiral and shape matters. I really appreciate this [1] post though. [1] https://news.ycombinator.com/item?id=30892299 https://news.ycombinator.com/item?id=30892299
- forgotmypw17 5y agoIn sexual selection, a type of evolutionary selection driven by mate choice rather than raw survival fitness, yes, that piece of Darwin's writing which was suppressed by Victorian ideology for about 100 years until being rediscovered in the 1960s, symmetry is an easy show of control over the physical enviroment. By making more than one of identical somethings, you're showing that it was not through chance or accident that you developed this piece, but through deliberate growth and control, and you can prove it, because you've made two or more of them, and the viewer can easily check them against each other.
- systemvoltage 5y agoA deeper way to think about this is that any phenomenon that pumps out entropy from the system by injecting work + heat tends to stand up like a sore thumb in the rather dull sponteneaty of nature. I don't mean entropy in the naive sense (order vs disorder), but as dispersal of energy (third law). Not sure what the cause of such locality is - perhaps we can call that intelligence?
- nemo 5y agoSymmetry appears in creatures that spawn out sperm into the sea and let it land where it may, and many other very simple life forms with non-sexual reproduction, or reproduction where attraction isn't a factor, as in most plants. I'm sure symmetry may also add attractiveness as a kind of fitness display, but it's a much more fundamental thing since it's also present in life forms like plants which do evolve through sexual selection but without animalian fitness displays, and in non-sexually reproducing life forms.
- seba_dos1 5y agoHave you ever seen how symmetrical human faces look like? Do you consider them more attractive than regular, asymmetrical ones?
- forgotmypw17 5y agoAren't most human faces largely symmetrical, save for minor differences?
- 2OEH8eoCRo0 5y agoI always just assumed that it can be expressed with very little information so it's simpler. Simpler things are more likely to happen via random processes.
- pshc 5y agoMy just-so guess is that it’s way easier to keep one’s balance when symmetrical, especially while locomoting.
- pgt 5y agoFirst thought: sensor and emitter are also symmetrical.
- COGlory 5y agoThis has been well known for years and years in the structural biology and molecular evolution fields. Strange to see this get attention suddenly.
- spoonjim 5y agoAlmost every vehicle or functional structure that humans have engineered has an axis of symmetry. Animals have symmetry for the same reason.
- Tagbert 5y agoThere are multiple kinds of symmetry. In general they are characterized by a simple unit that is repeated and transformed in some way. Mirror symmetry - this is what people typically think of when they talk of symmetry. In this case the base unit is mirrored along an axis producing a copy with its geometry swapped across the axis. Rotation symmetry - here the unit is repeated by rotating it around an axis. Many plants and some animals like starfish exhibit rotational symmetry. Translation symmetry - the unit is shifted along an axis one or more times. A chain shows translation symmetry. Scaled symmetry - in this case the unit is scaled while repeated. A matryoshka doll would be an example. Symmetries can be combined in various combinations like rotation+scaled (Nautilus) One theory of why you see so much symmetry in biology is that it takes less information to build something using symmetry than specifying the whole directly. the genes of a centipede do something like specify "here is a body unit with legs" build more until a different gene says "stop". Even then, the gene specifing the body unit is more likely to specify "here is half a segment" and "stick a segment here and repeat that 4 times making each one smaller" to add the leg. This repetition of units takes less information and results in lots of symmetry as the units are transformed across different axes of symmetry. Fractals are another example of the repeating action producing repeating units with symmetry.
- thaumasiotes 5y ago> Translation symmetry - the unit is shifted along an axis one or more times. A chain shows translation symmetry. Worth noting that in the biological context this has its own dedicated term, "segmentation". > One theory of why you see so much symmetry in biology is that it takes less information to build something using symmetry than specifying the whole directly People have also observed that the environment is fundamentally indifferent to which direction you're facing (especially if you're capable of turning yourself). This goes a long way toward explaining why mirror and rotational symmetry might be a good idea even if they were more difficult to specify.
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- mistermann 5y ago
- mrfox321 5y agoCould this just be a bias of our ability to comprehend complexity? Humans are finitely intelligent. We cannot comprehend less symmetric systems. This may lead to publication bias. Less symmetric systems that defy human reasoning are associated to chaos and randomness.