How did life begin on Earth? Munich researchers find important clues

A study by Munich researchers takes a step forward in answering the question of how life arose on Earth.

In a groundbreaking experiment in the early 1950s, a scientist attempted to recreate the conditions of early Earth in a test tube. Stanley Miller put some simple ingredients that were thought to be swirling around in the young planet’s atmosphere and oceans into connected flasks, heated them, and applied electricity to them to simulate lightning. The results quickly became famous: the amino acids, the chemical building blocks of life, came from this primordial soup.

This discovery sparked a search in chemistry and biology for experiments that could help answer one of humanity’s greatest scientific questions: How did life begin on Earth? Now scientists at the Ludwig Maximilians University of Munich have taken an exciting step forward by showing how more complex molecules crucial to life could have been synthesized from the building blocks of the early Earth.

In their study, published in the journal Nature was published, the scientists swapped test tubes for tiny networks of branching cracks similar to those that form in rocks in nature. They flowed water along with key chemical building blocks through the cracks and then used heat to mimic a process that might occur near hydrothermal vents in the ocean or in porous rock near a geothermal pool.

They discovered that the heat flowing through these geological networks sorted and filtered the molecules, helping them form longer chains called biopolymers, which are essential for life. “This is fantastic evidence that simple physical processes can do something like this,” said Matthew Pasek, a geosciences professor at the University of South Florida who was not involved in the research.

Because the question of how life came to be is so large, it transcends the traditional boundaries that divide science into different disciplines. Chemists, biologists, astrophysicists and geologists are all at the table as they try to answer this question. Bridging these boundaries is what Christof Mast, biophysicist at the Ludwig Maximilian University of Munich, is interested in. His lab has designed an experimental setup that comes a little closer to the conditions under which the “prebiotic chemistry” from which life arose.

How did Earth concoct enough building blocks for life to emerge?

For decades, scientists have wrestled with the problem that early Earth was not a pristine laboratory with beakers, perfectly timed purification steps, and concentrated supplies of ingredients. It’s one thing to recreate the chemistry of life in the lab, but experiments feasible in a glass flask are unlikely at best in the chaotic conditions of the real world. “You can imagine the prebiotic soil, this prebiotic soup that is very diluted, and all these different things react in a very uncontrolled way,” Mast said.

One of the problems so far is that chemical reactions in the laboratory often produce byproducts that can trigger their own undesirable reactions, leaving scientists with only tiny amounts of the key material. So how did the early Earth concoct enough of these building blocks to eventually give rise to life?

To find out, the researchers cut branching networks of interconnected cracks in a tiny piece of an inert Teflon-like substance called FEP and clamped it between two sapphire plates. The sapphires were brought to precise but different temperatures to create a flow of heat through the geological network between them, mimicking the way heat likely flowed on early Earth – perhaps near volcanoes or hydrothermal vents . They then let water and chemical building blocks flow through the network of cracks and watched what happened.

Amino acids are important, but still far from life

In a proof-of-concept experiment, they used glycine, the simplest amino acid, along with a substance called TMP, which can react to join two glycine molecules. Such reactions are difficult in water, Mast said, and TMP was very rare on early Earth. When they simply mixed these ingredients together in a beaker or in geological fissures without heat, the amount of the more complex biopolymer they produced was “vanishingly small,” the researchers report.

However, when they introduced a thermal gradient into the cracks, the production of the biopolymer increased massively. This is significant because amino acids, although important, are still far removed from life. The same basic building blocks have also been found on lifeless meteorites, for example. “To reach the next level, you have to start making polymers – this is a fundamental step on the way to the next stage of life,” says Pasek.

The definitive question of how life arose cannot be answered with this setup: Was it in a pond, as might have existed on Earth’s surface, or near a hydrothermal vent, as found deep in the ocean? Heat flows through rocks could occur in a variety of geologic environments, Mast says, and were likely “ubiquitous” on early Earth.

The experimental setup can also be used to investigate other questions about early chemistry on the planet. Mast hopes to next create a network of cracks in geological material and build larger networks of interconnected chambers.

“The pot is important for cooking the ‘primordial soup’”

The study is another reminder that elegant chemical experiments can ignore a fundamental part of the primordial soup: the pot. In 2021, a team of scientists found that in the famous 1950s experiment, the test tube itself – or rather, the borosilicate glass from which it was made – played a role in the results. When the scientists repeated the experiment in a glass flask, a Teflon flask, and then a Teflon flask with a bit of borosilicate glass, they found that the glass played a crucial role in catalyzing the reactions.

“In other words, for cooking the ‘primordial soup,’ the pot is important,” Juan Manuel García-Ruiz, a research professor at the Donostia International Physics Center in Spain who was involved in the experiment, wrote in an email. He praised the new work for its imaginative approach and, perhaps most importantly, for being “geologically plausible.”

“It may not be the only mechanism, but it works and it is ingenious, and above all it is an experimental demonstration,” García-Ruiz said. “I think we need more experimental approaches to explore the geochemical context of the planet when life arose.”

We are currently testing machine translations. This article was automatically translated from English into German.

This article was first published in English on April 16, 2024 at the “Washingtonpost.com” – as part of a cooperation, it is now also available in translation to readers of the IPPEN.MEDIA portals.