Evolution: ancestor of all living things ate hydrogen

In laboratory experiments and computer simulations, the team tested the energy balance of the 402 basic reactions for various environmental conditions. It turned out that almost all of them run voluntarily and provide energy when the temperature is 80 to 100 degrees Celsius, the pH of the surrounding water is between 7 and 10 and certain starting materials are present – namely hydrogen, carbon dioxide, ammonia, hydrogen sulfide and phosphates. Such conditions are fulfilled in hydrothermal deep sea springs or in water-filled crevices in the earth’s crust. It is precisely these places that experts see as possible places in which life comes into being.

© Heinrich Heine University Düsseldorf (HHU), Jessica Wimmer (excerpt)

LUCA’s Putative Metabolism | The picture shows a network of metabolic reactions that could have taken place in LUCA, the hypothetical ancestor of all living things today. It shows 402 biochemical reactions that supply the basic components of the cell. Each circle represents a reaction, whereby the energy releasing is colored green, the energy absorbing purple (here calculated for 25 degrees Celsius and pH 7). Large gray diamonds indicate starting materials, small gray diamonds indicate reaction products.

“When the heat is strong enough, the pH value is high enough and there is sufficient substance replenishment, the system of basic metabolic reactions tends to maintain itself – without proteins or enzymes having an effect,” explains Wimmer. That is important with regard to the first living beings. “At the beginning of biochemical metabolism about four billion years ago, the enzymes that enable the reactions in today’s cells did not exist because they had not yet developed. The metabolism had to result from reactions that took place spontaneously in the environment at that time, perhaps with the help of inorganic catalysts. “

Hot water in hydrothermal deep sea springs contains chemically reducing hydrogen, which is created when rocks are transformed. It reacts with carbon dioxide, which is also dissolved in water, from which hydrocarbons such as methane emerge, which living things can then utilize. Ammonia, hydrogen sulfide and other ingredients of organic compounds are also formed under hydrothermal conditions. “Rock surfaces with transition metals catalyze such reactions, which means they promote them,” says Wimmer. This can be copied in the laboratory.


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