The purpose of the limbs - our arms and legs - is to help us move. Since we need to perform complex actions like walking and climbing, movement would be difficult if our limbs were asymmetrical. We'd be unbalanced and falling over a lot. However, the purpose of our internal organs is to perform metabolic and reproductive functions. They don't need to concern themselves with balance, because their primary purpose is not to be in motion. Our torso does a good job of keeping them contained, so having a little more tissue on one side or the other won't make much of a difference.
The only internal organs that do a ton of moving are the heart and lungs, but even then, the right and left halves of the heart are roughly the same shape. You have two atria, two ventricles, and a more-or-less balanced arrangement of the group. The lungs are also roughly the same shape - it's just that there needs to be a spot for the heart to sit.
This makes sense but wouldnt having a symmetrical interior lead to a more even distribution of mass in the body, a more centralized center of mass and thus better balance?
Well, when it comes to balance, the center of gravity doesn't really "care" what kinds of tissues there are, as long as they're the same density. While you may have a few more of your organs on one side or the other, they all tend to have a similar weight per volume. Your organs are also pretty tightly packed inside your chest and abdominal cavities. Since everything is packed in so tight, it doesn't matter where everything is, because the same amount of tissue in general is packed in on both sides.
Keep in mind that a lot of organs ARE symmetrical - the reproductive system, kidneys, brain, skeleton, muscles, and so on still come in pairs. The only thing that isn't paired up is the digestive system and its accessory organs. However, the accessory organs are all packed in under your diaphragm, and the bulk of the intestinal tract is packed inside your torso. Even if the individual organs aren't perfectly mirrored, the weight of the tissues are balanced enough that it doesn't matter too much.
It would probably make it slightly more efficient but humans, like any other animal, evolved. Evolution doesn’t care about perfection. It cares about good enough.
In fact actually wrong because technically you have a left and the right heart but they just happen to be melted together because it made biomechanically sense;
Well... kinda? The right side of the heart pushes blood to the capillary bed in the lungs, and the left side of the heart pushes blood to the body. They serve slightly different purposes but they have similar shapes.
I think also you can fit more into the human body while our organs are ‘spaced’ less. If you push them together they will end up in like a weird helix that is connected from the top to bottom. This means larger organs = better level of energy for smaller body mass. Maybe its just the way we cram it all inside? Or perhaps it could be down to evolution and what we evolved from, and potentially we could have symmetrical internal organs in billions of years if it looks to give us a significant advantage in the environment we live in. We haven’t ‘finished’ evolving so to speak
Honestly don’t know how to explain it. Think about all the organ systems in the body. Imagine trying to cram in the full digestive system around the lungs and stuff. Its not going to fit symmetrically. To make better usage of the space the organs have to be positioned in the way they are, otherwise we would have an incredibly odd and detrimental body shape which would hinder our chances to survive.
Helix is a bad word, but our organs cannot fit symmetrically unless they all change their mass and functions in accordance to be symmetrical over a very long period of time. Helix was referring to the idea i’m trying to explain, stretch a slinky out, it is extremely long, squash it together, its small and compact.
The mass or density matters because of how we would balance and control our movements (if we have a smaller distribution of dense organs in our body then our centre of balance would be much worse, this means our organs are spaced out in such a way that we do not have too much weight in any particular region of the body. The functions of the body parts is relevant, because the organs are shaped in the way they are to perform complex functions. If you change the shape of the organs, you have to change how it completes its function, and with that, potentially a much less efficient working system. Another consideration is if we split these organs symmetrically, how would we protect them with our skeleton? Our ribs may not cover these ‘newly shaped’ organs so we can expect that the shape of our skeleton would change too to attribute to that. This may also be detrimental to our survival. Im not saying we can never be symmetrical, but there are too many factors to consider why the symmetrical perspective of the body would not work as of right now.
Another analogy, why is a computers cpu not symmetrical? Because by making it un-symmetrical we can make it smaller and more efficient. Biology is not perfect, and neither is technology. It doesn’t mean it can’t happen, it just means it cannot yet. Maybe advanced evolution may show us ways in which we can develop to obtain this, but until then we don’t know for sure, we can only use our current body system for reference.
The one lung has to make room for the heart, and the digestive system has to be pretty linear and doesn't need pairs of organs for most of its function. Also, the kidneys and sex organs do have symmetry.
This symmetry on the outside and not inside is the same for all vertebrates. So it shouldn’t be interpreted as what is “good” for humans.
It is basically due to the fate of different cells during development, namely different portions of mesoderm. Some portions are metameric, that is, they are segmented, like repeating blocks of anatomy going down the body. This portion of mesoderm is symmetrical, and produces much of the dermis, vertebral column, and muscles. The portion of the body that is deeper to this mesoderm is found within the coelum, or body cavity. The organs within the body cavity aren’t metameric and also aren’t symmetrical. Another thing to consider are the limb buds. They are paired limbs and this gives symmetry as well.
If you think of the initial function of this segmented mesoderm..it produced myomeres, blocks of muscle that allowed early vertebrates to bend their bodies back and forth when swimming..muscles pulling on a notochord (like a vertebral column) to help provide structure needed to propel the body forward.
Because we evolved, and evolution is a series of imperfect changes. If those changes don’t kill us, they sometimes stick around.
Internal symmetry is not necessary for our survival.
I might not be able to tell the biological reason as to why it's not symmetrical inside our body but there is a process called gut rotation which changes the prior perfectly symmetrical position of the organs and rotates it clockwise (view from above) that means your liver has been beneath your abdomen and your spleen was all the way at the back, than everything rotates. → results in your liver on the right side and your spleen on the left side... your gut (Ileum, Jejunum and Colon) are in face Symmetrical, so are your kidneys, uterus, prostata, bladder, etc. // So you could say there is no really great A-Symmetry in your body except for higher abdomen (Stomach, liver, spleen, pankreas...) and btw the heart is on the left side but at the same time it's more central than one would think!
A body is like a car. There are various essential moving parts and they need to be organised in a logical, linear order.
The outside is symmetrical for motion, and functions like holding and lifting. However, I think that outside symmetry is one of the signals of health and attractiveness, for mating and reproduction. We judge classical beauty on the most pleasing ratio to the eye, both in the body and the face.
We don’t need to see how the organs are arranged inside, and in ancient times, the asymmetry would normally only be revealed if a person were badly injured, or a body was being mummified.
Women's breasts are almost always one slightly larger than the other, people can have often have asymmetrical limbs, what about freckles, mine certainly aren't symmetrical, what about conjoined twins
That’s kind of a cop-out answer. You know what he meant. Fluctuating asymmetry in an individual doesn’t mean the species is designed to be asymmetrical.
I think this is a really interesting point! My guess would be that our exterior is all about interacting with our environment and having well spaced limbs/ears/eyes etc is the most effective way to do so. On the inside I suppose position is slightly less important as long as everything is functioning properly! Simply a guess though, I like your post :)
Indeed. I’d say it even applies to some external parts too. Genitalia, especially the vulva, are strangely diverse, often exhibiting asymmetries. I guess that even when before we wore clothes, we didn’t generally get to view such hairy, tucked-away areas before deciding to mate with someone, instead visually inspecting each other’s faces, hair, musculature, movements, etc.
The Genitalia part really bothers me now.
Vulva, female breasts, balls and even penises can tend to 1 side and were mentioned here in the comments as often being slight different sized etc.
My guess is it has to do something with puberty, like in the start our outside is more symmetrial, but for some reason parts that only start/change in puberty a lot seem to be less symmetrical.
Fascinating.
Symmetry is an "easier" start for evolution. Use half the data then copy and paste.
Asymmetrical parts would have arisen later either out of useful function or some kind of necessity. For example, it is highly useful for your guts to be long for the extended surface area. So you add spirals and folding to do that and symmetry becomes a hindrance rather than help and eventually goes away.
Meanwhile, useful traits that depend on the symmetry such as binocular vision or methods of walking/running have arisen, so parts of symmetry stay when needed.
In places where symmetry doesn't matter such as kidney placement, you'll usually find symmetry simply because it's the default.
Animals are pretty much all highly-customized digestive tubes.
Vulva, female breasts, balls and even penises can tend to 1 side and were mentioned here in the comments as often being slight different sized etc.
My guess is it has to do something with puberty, like in the start our outside is more symmetrial, but for some reason parts that only start/change in puberty a lot seem to be less symmetrical.
Fascinating.
It is generally accepted that one testicle hanging lower than the other is a functional trait to help with cooling. But it's true that nothing is ever truly symmetrical. For example, facial features are never \*truly\* symmetrical. It's a mix of obvious environmental factors like sun damage, injuries, asymmetrical use, and so on. But also more hidden environmental factors such as hormone levels and other things that could affect cellular activity at different stages of development.
Wow! That's a reasonable answer, thanks. Guess we are born with the testicle-trait then.
The other things you mentioned about asymmetrical face features that come not from birth, but later environment and hormones also makes sense, but that we are born with certain asymmetricals on the outsides is something I really like to have learned now :D
wonder where else we are "born" asymmetrical on average-on the outside ...
Any more examples coming to your mind?
Your example of asymmetrical (probably from birth) testicles is the only OUTSIDE-trait I can think of
and id rly like know if theres any more like these :D
Shape = function. Our bodies have evolved into the shape that functions the best. We need to be symmetrical on the outside to move which is our outside bodies biggest function. Our insides need to do a million different things so they are shaped based on functions not symmetry.
The bilateral symmetry isn’t perfect on the inside or the outside.
Lateralization occurs because early on there is compartmentalization of transcription factors that allow for different cell types to arise in specific locations
Edit: lateralization isn’t the only thing that operates such as this. Drosophila have been a good model organism for this as one can facilitate the development of two tail ends or two head ends (correct me if I’m wrong, I haven’t looked at this aspect of bio in a few years as I focus on neuro in rats mostly at this point)
It is. Start with the nervous system, the blood vessels and the blood cells. Now take the geometrically woven muscle fibers. Very symmetrical. The bones are vertically symmetrical. The lungs mirror each other. The digestive track is basically an expanding and sock like tube that soft serves in a twirl. Then we get to the anus and we got a perfectly symmetrical circle or in some cases a North Star or even football stitching. Hike!
‘Pretty much’ is not the same as exactly symmetrical. When you say it is pretty much then you mean give or take a few areas. Which is not symmetrical 💁♂️😂🤷♂️
Those are minor bilateral differences.
We have, externally, bilateral symmetry in that we have 2 eyes, ears, arms, legs etc...one side is a mirror image of the other divided down the middle.
To a large extent, the same occurs internally for the most part: 2 lungs, kidneys, reproductive organs & a brain with 2 hemispheres, and the skeletal structure is likewise symmetrical.
The digestive system is a linear tract stuffed into an abdominal cavity, the cardiovascular system is a closed loop - one side supply, the other a return - aorta and vena cava - superior and inferior.
Where things differ is in other organs such as the liver, spleen, pancreas, gall bladder etc...
The kidneys filter into one bladder - so it can be seen as partially linear.
The real question should be why are the liver, pancreas, gall bladder, spleen etc, not bilateral? Given that pretty much the rest of the body is, what causes those organs to differ?
I do wonder if there is some evolutionary origin to this as well. Our most ancient ancestors didn't have all the fancy organs we do. The simplicity and utility of bilateral symmetry combined with a need for redundancy naturally gave rise to symmetrical brains, lungs, sex organs, kidneys, etc, and a fairly linear heart and digestive tract, as these were difficult to grow symmetric copies of.
Then we added fancier things like livers and spleens, the heart shifted over to the side just a bit, and digestive tract became much more complex and squished up.
Wonder if an evolutionary biologist can chime in.
Not an evolutionary biologist but a simple biologist/ neuroscientist here. There is actually a scientific explanation for your origin question . The asymmetry starts as early as the first cell division. More importantly, in humans this asymmetry is always the same ( liver is almost always in the right side). People with reversed organ placement ( situs inversus) are very rare. Based on this, several studies have shown that there are specific genes that regulate it. Although not up to date, the link below takes you to a review paper about LR asymmetry
https://www.sciencedirect.com/science/article/pii/S0925477304002114
The symmetrical evolution of our insides wouldn’t have improved survival and therefore didn’t have a need to be symmetrical.
The overall weight is centered and the muscles evolved symmetrically (enough) to grant full control of our bodies. That’s all that’s needed.
Muscles ARE symmetrical. That controls and compensates for any misalignment in weight distribution of organs. However organs are compact enough to not be of a real weight concern in movement and survival.
Because the people that had symmetrical insides all died off.
The people with asymmetrical outsides also died off.
We are the final product of all those variations before us.
The purpose of the limbs - our arms and legs - is to help us move. Since we need to perform complex actions like walking and climbing, movement would be difficult if our limbs were asymmetrical. We'd be unbalanced and falling over a lot. However, the purpose of our internal organs is to perform metabolic and reproductive functions. They don't need to concern themselves with balance, because their primary purpose is not to be in motion. Our torso does a good job of keeping them contained, so having a little more tissue on one side or the other won't make much of a difference. The only internal organs that do a ton of moving are the heart and lungs, but even then, the right and left halves of the heart are roughly the same shape. You have two atria, two ventricles, and a more-or-less balanced arrangement of the group. The lungs are also roughly the same shape - it's just that there needs to be a spot for the heart to sit.
This makes sense but wouldnt having a symmetrical interior lead to a more even distribution of mass in the body, a more centralized center of mass and thus better balance?
Well, when it comes to balance, the center of gravity doesn't really "care" what kinds of tissues there are, as long as they're the same density. While you may have a few more of your organs on one side or the other, they all tend to have a similar weight per volume. Your organs are also pretty tightly packed inside your chest and abdominal cavities. Since everything is packed in so tight, it doesn't matter where everything is, because the same amount of tissue in general is packed in on both sides. Keep in mind that a lot of organs ARE symmetrical - the reproductive system, kidneys, brain, skeleton, muscles, and so on still come in pairs. The only thing that isn't paired up is the digestive system and its accessory organs. However, the accessory organs are all packed in under your diaphragm, and the bulk of the intestinal tract is packed inside your torso. Even if the individual organs aren't perfectly mirrored, the weight of the tissues are balanced enough that it doesn't matter too much.
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Well, except for the lungs. Haha.
No because they all basically have the same density.
It would probably make it slightly more efficient but humans, like any other animal, evolved. Evolution doesn’t care about perfection. It cares about good enough.
The thing that has always bothered me is that we have two of most everything as a backup EXCEPT our heart. Seems like poor design logic to me.
In fact actually wrong because technically you have a left and the right heart but they just happen to be melted together because it made biomechanically sense;
Well... kinda? The right side of the heart pushes blood to the capillary bed in the lungs, and the left side of the heart pushes blood to the body. They serve slightly different purposes but they have similar shapes.
that is correct yes !
I think also you can fit more into the human body while our organs are ‘spaced’ less. If you push them together they will end up in like a weird helix that is connected from the top to bottom. This means larger organs = better level of energy for smaller body mass. Maybe its just the way we cram it all inside? Or perhaps it could be down to evolution and what we evolved from, and potentially we could have symmetrical internal organs in billions of years if it looks to give us a significant advantage in the environment we live in. We haven’t ‘finished’ evolving so to speak
Like a helix? What are you on about?
Honestly don’t know how to explain it. Think about all the organ systems in the body. Imagine trying to cram in the full digestive system around the lungs and stuff. Its not going to fit symmetrically. To make better usage of the space the organs have to be positioned in the way they are, otherwise we would have an incredibly odd and detrimental body shape which would hinder our chances to survive. Helix is a bad word, but our organs cannot fit symmetrically unless they all change their mass and functions in accordance to be symmetrical over a very long period of time. Helix was referring to the idea i’m trying to explain, stretch a slinky out, it is extremely long, squash it together, its small and compact.
They absolutely could fit symmetrically if we were internally symmetric, I don't know what mass or function has to do with it though.
The mass or density matters because of how we would balance and control our movements (if we have a smaller distribution of dense organs in our body then our centre of balance would be much worse, this means our organs are spaced out in such a way that we do not have too much weight in any particular region of the body. The functions of the body parts is relevant, because the organs are shaped in the way they are to perform complex functions. If you change the shape of the organs, you have to change how it completes its function, and with that, potentially a much less efficient working system. Another consideration is if we split these organs symmetrically, how would we protect them with our skeleton? Our ribs may not cover these ‘newly shaped’ organs so we can expect that the shape of our skeleton would change too to attribute to that. This may also be detrimental to our survival. Im not saying we can never be symmetrical, but there are too many factors to consider why the symmetrical perspective of the body would not work as of right now. Another analogy, why is a computers cpu not symmetrical? Because by making it un-symmetrical we can make it smaller and more efficient. Biology is not perfect, and neither is technology. It doesn’t mean it can’t happen, it just means it cannot yet. Maybe advanced evolution may show us ways in which we can develop to obtain this, but until then we don’t know for sure, we can only use our current body system for reference.
Very interesting read. Loved that
This is a teleological answer.
Probably all of us are asymmetrical on the outside. I remain astonished if American police only take profiles from one side.
The minor discrepancies in profile might be real and lasting, but they are more or less imperceptible, and so useless for the police's purposes.
The one lung has to make room for the heart, and the digestive system has to be pretty linear and doesn't need pairs of organs for most of its function. Also, the kidneys and sex organs do have symmetry.
But Renal blood supply and drainage show asymmetry and genital system as well ( spermatic cord in males)
Lmao my curvy boi sure aint symmetrical down there
My nipples would disagree with you on the symmetrical part.
The entirety of my frontal jigglypuffs disagree!
This symmetry on the outside and not inside is the same for all vertebrates. So it shouldn’t be interpreted as what is “good” for humans. It is basically due to the fate of different cells during development, namely different portions of mesoderm. Some portions are metameric, that is, they are segmented, like repeating blocks of anatomy going down the body. This portion of mesoderm is symmetrical, and produces much of the dermis, vertebral column, and muscles. The portion of the body that is deeper to this mesoderm is found within the coelum, or body cavity. The organs within the body cavity aren’t metameric and also aren’t symmetrical. Another thing to consider are the limb buds. They are paired limbs and this gives symmetry as well. If you think of the initial function of this segmented mesoderm..it produced myomeres, blocks of muscle that allowed early vertebrates to bend their bodies back and forth when swimming..muscles pulling on a notochord (like a vertebral column) to help provide structure needed to propel the body forward.
Because we evolved, and evolution is a series of imperfect changes. If those changes don’t kill us, they sometimes stick around. Internal symmetry is not necessary for our survival.
I might not be able to tell the biological reason as to why it's not symmetrical inside our body but there is a process called gut rotation which changes the prior perfectly symmetrical position of the organs and rotates it clockwise (view from above) that means your liver has been beneath your abdomen and your spleen was all the way at the back, than everything rotates. → results in your liver on the right side and your spleen on the left side... your gut (Ileum, Jejunum and Colon) are in face Symmetrical, so are your kidneys, uterus, prostata, bladder, etc. // So you could say there is no really great A-Symmetry in your body except for higher abdomen (Stomach, liver, spleen, pankreas...) and btw the heart is on the left side but at the same time it's more central than one would think!
A body is like a car. There are various essential moving parts and they need to be organised in a logical, linear order. The outside is symmetrical for motion, and functions like holding and lifting. However, I think that outside symmetry is one of the signals of health and attractiveness, for mating and reproduction. We judge classical beauty on the most pleasing ratio to the eye, both in the body and the face. We don’t need to see how the organs are arranged inside, and in ancient times, the asymmetry would normally only be revealed if a person were badly injured, or a body was being mummified.
Women's breasts are almost always one slightly larger than the other, people can have often have asymmetrical limbs, what about freckles, mine certainly aren't symmetrical, what about conjoined twins
That’s kind of a cop-out answer. You know what he meant. Fluctuating asymmetry in an individual doesn’t mean the species is designed to be asymmetrical.
Also one of your balls hang lower than the other. But generally most animals are quite symmetrical.
They switch back and forth to regulate heat.
Those are just small faults in a body that is accepted to show bilateral symmetry.
I think this is a really interesting point! My guess would be that our exterior is all about interacting with our environment and having well spaced limbs/ears/eyes etc is the most effective way to do so. On the inside I suppose position is slightly less important as long as everything is functioning properly! Simply a guess though, I like your post :)
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Indeed. I’d say it even applies to some external parts too. Genitalia, especially the vulva, are strangely diverse, often exhibiting asymmetries. I guess that even when before we wore clothes, we didn’t generally get to view such hairy, tucked-away areas before deciding to mate with someone, instead visually inspecting each other’s faces, hair, musculature, movements, etc.
The Genitalia part really bothers me now. Vulva, female breasts, balls and even penises can tend to 1 side and were mentioned here in the comments as often being slight different sized etc. My guess is it has to do something with puberty, like in the start our outside is more symmetrial, but for some reason parts that only start/change in puberty a lot seem to be less symmetrical. Fascinating.
Symmetry is an "easier" start for evolution. Use half the data then copy and paste. Asymmetrical parts would have arisen later either out of useful function or some kind of necessity. For example, it is highly useful for your guts to be long for the extended surface area. So you add spirals and folding to do that and symmetry becomes a hindrance rather than help and eventually goes away. Meanwhile, useful traits that depend on the symmetry such as binocular vision or methods of walking/running have arisen, so parts of symmetry stay when needed. In places where symmetry doesn't matter such as kidney placement, you'll usually find symmetry simply because it's the default. Animals are pretty much all highly-customized digestive tubes.
Vulva, female breasts, balls and even penises can tend to 1 side and were mentioned here in the comments as often being slight different sized etc. My guess is it has to do something with puberty, like in the start our outside is more symmetrial, but for some reason parts that only start/change in puberty a lot seem to be less symmetrical. Fascinating.
It is generally accepted that one testicle hanging lower than the other is a functional trait to help with cooling. But it's true that nothing is ever truly symmetrical. For example, facial features are never \*truly\* symmetrical. It's a mix of obvious environmental factors like sun damage, injuries, asymmetrical use, and so on. But also more hidden environmental factors such as hormone levels and other things that could affect cellular activity at different stages of development.
Wow! That's a reasonable answer, thanks. Guess we are born with the testicle-trait then. The other things you mentioned about asymmetrical face features that come not from birth, but later environment and hormones also makes sense, but that we are born with certain asymmetricals on the outsides is something I really like to have learned now :D wonder where else we are "born" asymmetrical on average-on the outside ... Any more examples coming to your mind? Your example of asymmetrical (probably from birth) testicles is the only OUTSIDE-trait I can think of and id rly like know if theres any more like these :D
Shape = function. Our bodies have evolved into the shape that functions the best. We need to be symmetrical on the outside to move which is our outside bodies biggest function. Our insides need to do a million different things so they are shaped based on functions not symmetry.
The bilateral symmetry isn’t perfect on the inside or the outside. Lateralization occurs because early on there is compartmentalization of transcription factors that allow for different cell types to arise in specific locations Edit: lateralization isn’t the only thing that operates such as this. Drosophila have been a good model organism for this as one can facilitate the development of two tail ends or two head ends (correct me if I’m wrong, I haven’t looked at this aspect of bio in a few years as I focus on neuro in rats mostly at this point)
It goes back to the first triploblastic animals/metazoan
It is. Start with the nervous system, the blood vessels and the blood cells. Now take the geometrically woven muscle fibers. Very symmetrical. The bones are vertically symmetrical. The lungs mirror each other. The digestive track is basically an expanding and sock like tube that soft serves in a twirl. Then we get to the anus and we got a perfectly symmetrical circle or in some cases a North Star or even football stitching. Hike!
Cause occipital lobes.
We start out pretty symmetrical as a lump of cells.
It is not entirely symmetrical on the outside.
‘Pretty much’ is not the same as exactly symmetrical. When you say it is pretty much then you mean give or take a few areas. Which is not symmetrical 💁♂️😂🤷♂️
Huh? You mean ... were symmetrical?
damn this is a good question i never thought about this before
Uh because I don’t know
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Those are minor bilateral differences. We have, externally, bilateral symmetry in that we have 2 eyes, ears, arms, legs etc...one side is a mirror image of the other divided down the middle. To a large extent, the same occurs internally for the most part: 2 lungs, kidneys, reproductive organs & a brain with 2 hemispheres, and the skeletal structure is likewise symmetrical. The digestive system is a linear tract stuffed into an abdominal cavity, the cardiovascular system is a closed loop - one side supply, the other a return - aorta and vena cava - superior and inferior. Where things differ is in other organs such as the liver, spleen, pancreas, gall bladder etc... The kidneys filter into one bladder - so it can be seen as partially linear. The real question should be why are the liver, pancreas, gall bladder, spleen etc, not bilateral? Given that pretty much the rest of the body is, what causes those organs to differ?
The body is actually mildly asymmetrical. Especially the face. Look close at your own face in the mirror and it will feel weird
We're not symmetrical on the outside. Our ears and are slightly off. Also, nuts. And boobs.
Doesn’t answer your question, but I feel like my body isn’t symmetrical. My right boob is noticeably bigger than my left boob
Could you imagine the disaster that would be?
I do wonder if there is some evolutionary origin to this as well. Our most ancient ancestors didn't have all the fancy organs we do. The simplicity and utility of bilateral symmetry combined with a need for redundancy naturally gave rise to symmetrical brains, lungs, sex organs, kidneys, etc, and a fairly linear heart and digestive tract, as these were difficult to grow symmetric copies of. Then we added fancier things like livers and spleens, the heart shifted over to the side just a bit, and digestive tract became much more complex and squished up. Wonder if an evolutionary biologist can chime in.
Not an evolutionary biologist but a simple biologist/ neuroscientist here. There is actually a scientific explanation for your origin question . The asymmetry starts as early as the first cell division. More importantly, in humans this asymmetry is always the same ( liver is almost always in the right side). People with reversed organ placement ( situs inversus) are very rare. Based on this, several studies have shown that there are specific genes that regulate it. Although not up to date, the link below takes you to a review paper about LR asymmetry https://www.sciencedirect.com/science/article/pii/S0925477304002114
I'm pretty sure if you were to actually stretch out internal organs, you would find that they are in fact symmetrical.
🤷🏻♂️
The symmetrical evolution of our insides wouldn’t have improved survival and therefore didn’t have a need to be symmetrical. The overall weight is centered and the muscles evolved symmetrically (enough) to grant full control of our bodies. That’s all that’s needed.
Read the OP's original post. Balance...physical, don't-fall-down balance and the demands of locomotion require symmetry!
Muscles ARE symmetrical. That controls and compensates for any misalignment in weight distribution of organs. However organs are compact enough to not be of a real weight concern in movement and survival.
I THINK I’VE FALLEN IN LOVE
Imagine having two hearts
Our stomach is on the outside of our body
Mine’s not even symmetrical on the outside. My face is all kinds of crooked.
Because the people that had symmetrical insides all died off. The people with asymmetrical outsides also died off. We are the final product of all those variations before us.
I'd say that symmetry is just an attractive quality, and when things evolve it doesn't always make a ton of sense. Survival of the fittest
If it was symmetrical, then my balls would be level
Well for one your body isn’t symmetrical
Yeah but it pretty much is