Symmetry is more often the norm than the exception in biology. Our bodies contain left and right sides, starfish radiate from a central point, and even trees produce symmetrical blossoms, while not being generally symmetrical. By comparison, asymmetry in biology appears to be fairly uncommon.
Does this imply that symmetry is preferred by evolution? According to a recent study headed by Iain Johnston, a professor in the Department of Mathematics at the University of Bergen in Norway, the answer is yes.
Even though symmetrical structures account for just a small percentage of all potential shapes — at least in geometry – symmetry appears in living beings. It’s not only a matter of physical type, though.
Proteins, the body’s molecular machinery, are also essentially symmetrical, consisting of a set of recurring, modular pieces. Animals, too, have repetitive structures; consider centipedes, which have repeated body segments.
This apparent “preference” is not motivated by aesthetic considerations. Instead, it boils down to simplicity, according to the experts.
In the current study, Johnston and his co-authors write, “It might be tempting to infer that symmetry and modularity result via natural selection.” Because advantageous features aid survival, natural selection might encourage them to grow more widespread.
Natural selection, on the other hand, can only make a favorable feature more prevalent or eliminate a bad one; it can’t create new ones.
Natural selection may also appear to prefer symmetry because it is frequently presented with symmetrical forms to deal with. The most plausible explanation for why proteins and bodies are symmetrical is because more symmetrical, recurring forms develop in the first place, rather than because symmetry provides a survival benefit.
So, what causes this to occur? Because symmetrical shapes generally need less information to develop than asymmetrical forms, they have likely evolved more frequently and subsequently survived across evolutionary time.
In a statement, Johnston added, “Imagine having to teach a buddy how to tile a floor in as few words as possible.” “Place diamonds here, long rectangles here, wide rectangles here,’ you wouldn’t say. ‘Place square tiles all over the place,’ you’d say. And the result of this simple, straightforward technique is beautifully symmetrical.”
Using computational modeling, Johnston and his colleagues put the simplicity hypothesis to the test. The researchers discovered that random mutations are considerably more likely to produce basic genetic sequences than complicated ones after simulating protein evolution.
Natural selection can then take over and make use of those simple structures if they are good enough to accomplish their jobs. High-symmetry structures with low symmetry were seen in the researchers’ simulations as well as in real life.
The research gives a novel twist to the so-called endless monkey theorem, a well-known thought experiment in evolutionary biology. If a monkey types at random for an endless amount of time, as predicted by the theorem, it will eventually generate the whole works of Shakespeare (or perhaps the script for “Die Hard”).
Random mutations in DNA are essentially typing monkeys. It’s a given that given enough time (and monkeys), some clever mutations will emerge.
However, by the time a hypothetical monkey completes Shakespeare’s whole body of work, the hardworking creature will have typed a significant number of little poems. Likewise, biology relies solely on genetic instructions generated at random (much like the work of a random number generator).
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