Death allows for complexity in chemical evolution

Simple systems can be reproduced faster than complex systems. So, how could the complexity of life have come about from a simple chemical beginning? Starting with a simple system of self-replicating fibers, chemists from the University of Groningen have found that when introducing a molecule that attacks the replicators, the more complex structures have an advantage. This system points the way forward by clarifying how life can arise from inanimate matter. The results were published in the journal March 10 applied chemistry

The path to the answer to the question of how life originated is guarded by Spiegelman’s monster, named after the American molecular biologist Sol Spiegelman, who some 55 years ago described the tendency of replicators to shrink if they were allowed to evolve. “Complexity is a disadvantage during replication, so how has the complexity of life evolved?” asked Sijbren Otto, professor of System Chemistry at the University of Groningen. He previously developed a self-replicating system in which self-replication produces fibers from simple building blocks, and now he has found a way to defeat the monster.

Death

“To achieve this, we introduced death into our system,” explains Otto. Its fibers are made up of stacked rings that are themselves composed of loose building blocks. The number of building blocks in a ring can vary, but stacks always contain rings of the same size. Otto and his team adapted the system to create rings of two different sizes, with three or six building blocks.

Under normal circumstances, fibers made up of small rings will outgrow the fibers with larger rings. “However, when we added a compound that breaks rings in the fibers, we found that the larger rings were more resistant. This means that the more complex fibers will dominate, despite the smaller rings replicating faster. more easily ‘killed’. ‘

Experiments

Otto recognizes that the difference in complexity between the two types of fibers is small. “We did find that the fibers from the larger rings were better catalysts for the benchmark retro-aldol reaction than the simpler fibers made from three-building rings. But again, this reaction does not benefit the fibers.” However, the added complexity protects the fibers from destruction, likely by shielding the sulfur-sulfur bonds connecting the building blocks in rings.

“All in all, we have now shown that it is possible to defeat Spiegelman’s monster,” says Otto. “We’ve done this a certain way, by introducing chemical destruction, but there may be other routes. For us, the next step is to figure out how much complexity we can create in this way.” His team is now working on a way to automate the response that depends on a delicate balance between the processes of replication and destruction. “Right now it needs constant supervision and this is limiting the time we can run it.”

Variants

The new system is the first of its kind and opens the way to a more complex chemical evolution. “To achieve a true Darwinian evolution that leads to new things, we need more complex systems with more than one building block,” says Otto. The trick will be to design a system that allows for the right amount of variation. “If you have unlimited variation, the system isn’t going anywhere, it just produces small amounts of all kinds of variations.” On the other hand, if there is very little variation, nothing really new will appear.

The results presented in the last paper show that, starting from simple precursors, complexity can increase over the course of evolution. “This means that we can now see a way forward. But the journey to producing artificial life through chemical evolution is still a long way off,” says Otto. However, he has defeated the monster guarding the way to his destination.