Why are Some Living Things Symmetric?

We can see that nature doesn’t have a concern about forming everything symmetrically, when we look at a scenery, trees or clouds. Nevertheless, there must be a benefit in having a symmetrical appearance for some living beings, because this feature  evolved and preserved itself for millions of years from the past to the present.

Symmetry is a simple and convenient verification method, which gives us information about whether other people are healthy or not.

We can only confirm information by comparing it with other information we expect to be the same. For example, when entering a system for the first time, you are asked to enter your password twice. The two passwords are expected to be the same for correct data input.  A symmetrical visual also contains two separate information, which are copies of each other. When looking at a person, we compare their left and right sides without noticing. If there is a significant difference between the two halves, this condition is recognized as an abnormality. Physical defects or acquired diseases aren’t expected to show themselves in perfect symmetry, because symmetry occuring in nature spontaneously is actually a condition with very low possibility. Briefly stated, symmetry, is a simple and convenient verification method, which gives us information about whether other people are healthy or not. In a world where people weren’t symmetrical, it wouldn’t be easy for us to tell whether a boil in the middle of a face was a sign of a disease or not.

It is important to tell whether the opposite sex is healthy or not, because every person would like to have healthy children carrying their own genes. The feature of humans’ physical appearances being symmetrical provided convenience and advantage for our ancestors, from millions of years in the past, when determining the health state of others, and was transferred to future generations through sexual selection. This approach also shows why the symmetric feature isn’t observed on sponges living in the depths of the ocean or on the trunks of olive trees, but especially on living beings which choose their own partners and reproduce sexually.

But, sexual selection isn’t the only reason for symmetry. Think of a Ferrari with a left mirror twice the size of the other one. This car would pull to the left at high speeds. The vehicle would have to spend extra energy in means to compensate for this situation. Every creature, which needs to move in order to hunt for its prey or run from its enemies in nature, must evolve towards the perfect symmetry, to be able to perform these activities with the least possible energy and peak efficiency. Individuals which have deformities in their symmetry, either starve to death or are hunted down, and can’t transfer their genes to future generations, due to their disadvantage.

Objects we want to be more symmetric, evolve towards more symmetrical forms with artificial selection.

There are objects which are symmetrical, even though they don’t match any of the rules I mentioned above. For example: fruits such as apples, strawberries or watermelons. When choosing apples at a greengrocer, do you have a tendency of choosing the perfect symmetrical ones or the deformed ones? We don’t want to eat an apple which is deformed, because of the prejudgement we make that it’s unhealthy, due to our obsession with symmetry. Farmers generate new trees from seeds, which give symmetric apples, in order to be able to sell their products, and also cut down the trees which give non-symmetrical fruits; and they put the most symmetric fruits they’ve produced for display. Therefore, objects we want to be more symmetric, evolve towards more symmetrical forms with artificial selection.

Let me ask you before you do. Well, then why is an olive seed symmetric even though we don’t eat it? Actually, fruits evolved so that animals eat them with their seeds and carry these indigestible seeds to other places by defecation, and in this way spread the seeds of trees over large areas. Would you swallow a symmetric, soft-edged seed easily and without noticing it, or a non-symmetrical and misshaped one? There probably were a few non-symmetric and misshaped olive seeds in the past, but the species of trees with these seeds were extinct because they couldn’t spread their seeds.

In conclusion, if symmetry is all around us, there must be a reason for it.

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