Why is the human body is symmetrical in exterior, but inside the stomach and heart is on left side? what advantages does it give to us?
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Evolutional traits don’t need to be advantageous, they just need to not be disadvantageous. The answer to a lot of these types of questions is simply: “it works well enough that way.”
Not sure about the heart/stomach in particular.
If you take two groups of any animal, and put them on two completely equal rooms for a very long time, they will look different eventually. Most of the time, evolution is random and does not yield any advantage. It could very well be that at one point, everyone with a right-side stomach died in a unrelated catastrophe, and now we only have left-side stomach individuals.
Symmetry is important for locomotion, stereovision and so on. The body parts that are relevant for those features are all symmetrical. The organs inside the chest cavity and stomach don’t require full or any symmetry. A long symmetric intestinal tract is practically impossible and organs of which we only need a single one can’t all accumulate right in the center of the body, so, over time, they shifted to one of the sides where there was space for them and that’s where we have them now.
Not every feature gives us an advantage. Some of them just don’t give us a big enough disadvantage to hurt our chances of survival.
On the outside, it makes sense that our eyes, ears, and limbs would be symmetrical because it allows us to move and sense the world around us better.
On the inside, it doesn’t really matter where our organs are located as long as they can do their jobs.
Your heart is actually located in the middle of your chest and tilted slightly to the left. The left side of your heart is bigger and accounts for about 2/3rds of the hearts mass. That coupled with the tilt makes it easy to think it’s positioned to the left, but it is not. It’s positioned the way it is so that the sternum and ribcage protect it. The stomach just so happens to be on the left side, there is not a specific evolutionary reason behind it.
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