You’ve surely noticed the symmetrical shapes scattered throughout nature. In the similarity between the left and right sides of your body, in the radial symmetry of a flower or in the five arms of a starfish.
It is certainly satisfying to note a mathematical aspect in natural forms, and it even seems natural to us that this is so. It gives us the impression of a certain engineering involved in the design of living beings. But the truth is that we don’t understand how a confusing process like evolution ends up prioritizing symmetrical shapes.
Would symmetrical shapes in general be more functional? In some cases it seems to us so, for mechanical reasons. It would be difficult for us to walk in a straight line if one of our legs was completely different from the other.
But other cases are less obvious. Nothing would prevent a flower from having several different petals, for example. Just like your heart isn’t right in the middle of your chest either.
A recent study from England (with the participation of the Brazilian Chico Camargo) suggests that the reason for the prevalence of symmetrical shapes in nature is not because they are necessarily more functional, but simply because they are easier to build.
Basically, using symmetric shapes would be a way to get more complexity with fewer instructions.
We tend to think of evolution as molding natural forms to perform some function. After all, we evolved eyes because we need to see. But in reality evolution shapes these forms only indirectly.
What evolution does is change the instructions for building the natural forms, encoded in DNA.
The resulting shapes are then judged by natural selection. Thus, the way in which forms are encoded is an important part of the evolutionary process.
In addition, these instructions are being written randomly in the DNA. To enhance natural forms, we have to wait for codings for innovations to emerge somewhat by chance, and then be selected by the evolutionary process. So it’s interesting to think of an algorithmic version of evolution.
An interesting analogy is the monkey on the typewriter, pressing random keys. Given enough time, eventually the monkey will end up writing the complete works of Shakespeare (as well as every possible book in every possible language).
Obviously, the ape would need an extremely long life for such an undertaking. But if we lowered our expectations to “just” one paragraph, we probably wouldn’t have to wait that long.
Thus, evolution is expected to prioritize shorter algorithms, simply because they are more likely. And the simplest way to achieve this is through the repeated use of functional modules.
Instead of planning each petal, you take the code to generate a petal and give it an instruction to repeat around the entire flower.
And so it is at all scales of life.
At the molecular level, protein complexes, viral capsids, and even RNA structures have symmetrical shapes.
The study authors simulated the evolution of these molecular structures from the instructions to generate them. In the case of a protein complex with over 13 million possible shapes, 30% of the time the algorithm resulted in one of five symmetric shapes arranged in a square.
Symmetries at more complex levels are inherited from the molecular level.
The complexity of more developed organisms usually results from breaking symmetries.
We ourselves don’t have the same radial symmetry as a jellyfish or an earthworm. But we still retain the same symmetries at the molecular level and the same parsimonious way of writing our DNA.
By understanding the simplicity of our construction rules at the most basic level, we can begin to understand the origins of our complexity.
