Symmetry runs rampant in nature. Wherever mirror images are repeated, such as in the right and left side of an elephant or butterfly, or around the center point, it is present in the repeated pattern of flower petals and starfish hands. It is also hidden in the structure of small things like proteins and RNA. While asymmetry certainly exists in nature (such as how your heart closes to one side of your chest, or how male fidler crabs have a large claw), symmetrical forms often grow to be random in living things.
Why does symmetry rule supreme? Biologists are not convinced – there is no reason for natural variation in such diverse forms of life and the prevalence of symmetry in their building blocks. Now it seems that a good answer can come from the field of computer science.
In a paper published this month in the Proceedings of the National Academy of Sciences, researchers analyzed thousands of protein complexes and RNA structures as well as model networks of molecules that control how genes are turned on and off. They found that evolution tended toward symmetry because the instructions for generating symmetry were easier to embed and follow in the genetic code. Symmetry is probably the most basic use of the saying “work smarter, not harder.”
“People are often amazed that evolution can create these wonderful creations, and what we’re showing is that it’s really easier than you think,” said Ard Lewis, a physicist and study author at Oxford University.
“It looks like we’ve got a new law of nature,” says Chico Camargo, co-author and lecturer in computer science at the University of Exeter in England. “It’s beautiful, because the way you look at the world changes.”
Dr. Lewis, Dr. Kemargo and his colleague Ian Johnst began researching the evolutionary origins of symmetry while Dr. Johnston received his Ph.D. Were working on, running simulations to understand how viruses form their protein shell. Emerging compositions were highly biased towards symmetry, which often grew out of what pure randomness allowed.
Researchers were surprised at first, but it made sense – algorithms for creating simple, repetitive patterns are easier to handle and harder to unscrew. Dr. Johnston, now at the University of Bergen in Norway, compares it to telling someone how to tile a floor: it is easier to give instructions for laying down repetitive rows of identical square tiles than to explain how to make a complex mosaic.
Over the next decade, researchers and their team applied the same concept to basic biological components, looking at how proteins gather in clusters and how RNA folds.
Dr. Camargo said.
The concept of RNA and proteins as small input-output machines implementing algorithmic genetic instructions illustrates the tendency towards symmetry in such a way that Darwinians could not “survive the fittest”. Because it is easier to encode instructions for creating simple, symmetrical compositions, nature chooses these simple instruction sets with an disproportionate number when it comes to natural selection. That makes evolution more like a “partisan game with loaded dice”, Dr. Camargo said its simplicity produces disproportionate symmetry.
While his paper focuses on microscopic structures, researchers believe that this logic extends to larger, more complex organisms. “If nature could reuse the program to create a petal instead of having a separate program for each of the 100 petals around the sunflower, it would be terribly meaningful,” said Dr. Said Johnston.
While there is still a gap between showing a statistical bias towards micro-symmetry and explaining the symmetry we see in plants and animals, biologist Hollow Gabor, who studies symmetry at the Hungarian University of Debrecen, says he is excited by the results of the new paper. . “It’s something to explain how such an innate and universal trait arises in nature, in evolution,” he said. Hollow, who was not involved in the study.
Similarly, Luis Cioa, a complex systems researcher at Spain’s Centro Nacional de Biotechnology, who was not involved in the study, described the work as “as legitimate as it gets.”
“There is a war going on between simplicity and complexity, and we live on its edge,” said Dr. Said Sion. The universe tends towards increasing randomness, he added, but these simple, symmetrical building blocks help to understand that complexity.