Endless forms most beautiful: Why evolution favors symmetry

Date:
March 14, 2022
Source:
The University of Bergen
Summary:
An international team of researchers from biology, computer
science and mathematics explains why evolution has a preference
for symmetry.



FULL STORY ==========================================================================
From sunflowers to starfish, symmetry appears everywhere in biology. This
isn't just true for body plans -- the molecular machines keeping our
cells alive are also strikingly symmetric. But why? Does evolution have
a built-in preference for symmetry?

==========================================================================
An international team of researchers believe so, and have combined ideas
from biology, computer science and mathematics to explain why. As they
report inPNAS, symmetric and other simple structures emerge so commonly
because evolution has an overwhelming preference for simple "algorithms"
-- that is, simple instruction sets or recipes for producing a given
structure.

"Imagine having to tell a friend how to tile a floor using as few words as possible," says Iain Johnston, a professor at the University of Bergen and author on the study. "You wouldn't say: put diamonds here, long rectangles here, wide rectangles here. You'd say something like: put square tiles everywhere. And that simple, easy recipe gives a highly symmetric
outcome." The team used computational modeling to explore how this
preference comes about in biology. They showed that many more possible
genomes describe simple algorithms than more complex ones. As evolution searches over possible genomes, simple algorithms are more likely to be discovered -- as are, in turn, the more symmetric structures that they
produce. The scientists then connected this evolutionary picture to a deep result from the theoretical discipline of algorithmic information theory.

"These intuitions can be formalized in the field of algorithmic
information theory, which provides quantitative predictions for the
bias towards descriptive simplicity," says Ard Louis, professor at the University of Oxford and corresponding author on the study.

The study's key theoretical idea can be illustrated by a twist on a famous thought experiment in evolutionary biology, which pictures a room full of monkeys trying to write a book by typing randomly on a keyboard. Imagine
the monkeys are instead trying to write a recipe. Each is far more likely
to randomly hit the letters required to spell out a short, simple recipe
than a long, complicated one. If we then follow any recipes the monkeys
have produced -- our metaphor for producing biological structures from
genetic information - - we will produce simple outcomes much more often
than complicated ones.

The scientists show that a wide range of biological structures
and systems, from proteins to RNA and signaling networks, adopt
algorithmically simple structures with probabilities as predicted by
this theory. Going forward, they plan to investigate the predictions that
their theory makes for biases in larger-scale developmental processes.


========================================================================== Story Source: Materials provided by The_University_of_Bergen. Note:
Content may be edited for style and length.


========================================================================== Related Multimedia:
* Strikingly_symmetric_molecular_machinery ========================================================================== Journal Reference:
1. Iain G. Johnston, Kamaludin Dingle, Sam F. Greenbury, Chico
Q. Camargo,
Jonathan P. K. Doye, Sebastian E. Ahnert, Ard A. Louis. Symmetry
and simplicity spontaneously emerge from the algorithmic nature
of evolution.

Proceedings of the National Academy of Sciences, 2022; 119 (11)
DOI: 10.1073/pnas.2113883119 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220314095742.htm

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