Death makes complexity in chemical evolution possible

Simple systems can reproduce faster than complex ones. So, how can the complexity of life arise as a result of a simple chemical beginning? Starting with a simple system of self-replicating fibers, chemists at the University of Groningen discovered that in introducing a molecule that attacks the replicators, the more complex structures have an advantage. This system shows the way forward to illustrate how life can arise from inanimate matter. The results were published in the journal on March 10. Applied Chemistry.

The way to answer the question of how life originates is guarded by Spiegelman’s monster, named after the American molecular biologist Sol Spiegelman, who about 55 years ago described the tendency of replicators to become smaller than they were allowed to develop has. “Complexity is a disadvantage during replication, so how did the complexity of life evolve?” asks Sijbren Otto, professor of systems chemistry at the University of Groningen. He previously developed a self-replicating system in which self-replication fibers produce 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,” Otto explains. Its fibers consist of stacked rings composed of single 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 so that rings were made of two different sizes, containing three or six building blocks.

Under normal circumstances, fibers consisting of small rings will outgrow the fibers with larger rings. “However, when we added a compound that breaks up rings inside the fibers, we found that the larger rings are more resistant. This means that the more complex fibers will dominate, although the smaller rings repeat faster. Fibers made from small rings be made easier “killed.” ‘

Experiment

Otto acknowledges that the difference in complexity between the two types of fibers is small. “We found that the fibers of the larger rings were a better catalyst for the standard retro-aldol reaction than the simpler fibers made from rings with three building blocks. But this reaction does not benefit the fibers either.” However, the extra complexity protects the fiber from destruction, probably by shielding the sulfur-sulfur bonds that bind the building blocks in rings.

“All in all, we have now shown that it is possible to beat Spiegelman’s monster,” says Otto. “We did it in a certain way by introducing chemical destruction, but there could be other routes as well. For us, the next step is to find out how much complexity we can create in this way.” His team is now working on a way to automate the response, which depends on a fine balance between the replication and destruction processes. “Right now, it needs constant oversight and it limits the time we can manage.”

Variant

The new system is the first of its kind and opens the way to more complex chemical evolution. “To bring about true Darwinist evolution leading to new things, we will need more complex systems with more than one building block,” says Otto. The trick is to design a system that allows the right amount of variation. “If you have unlimited variation, the system will go nowhere, it will only yield small quantities of all kinds of variants.” On the other hand, if there is very little variation, nothing really new will appear.

The results presented in the latest paper show that, according to simple precursors, the complexity may increase during the course of evolution. “That means we can now see a way forward. But the journey to the production of artificial life by chemical evolution is not long yet,” says Otto. However, he struck the monster that guarded the road to his destination.