The theory has been proven that life originated from non-biological substances in a small reservoir. This idea was previously expressed by Charles Darwin. We will tell you how our knowledge about the origin of life has changed.
What does the theory of the origin of life from the pond say?
The first, the most famous model of the origin of life on Earth belongs to Charles Darwin, who, in a letter to a friend of his, suggested that life arose in a kind of “shallow pond heated by the sun.”
Such reservoirs appeared on the planet’s surface during the fall of comets and meteorites several million years before the primary ocean appeared on it.
And until the end of the 70s of the XX century, until the very deep-sea expeditions to the faults took place, this hypothesis was the most popular. Other early twentieth century scholars, such as John Haldane and Alexander Oparin, agreed with Darwin and developed his theory.
They, independently of each other, suggested that the young Earth had a “restorative” atmosphere, that is, antagonistic to the one where oxygen is produced. In such an atmosphere, for example, iron will never rust. The atmosphere of that time may have been saturated with methane and ammonia, forming an ideal “primordial soup” from which life emerged in some shallow body of water.
This theory is supported by the fact that a number of critical elements for life were present on the land surface, for example, molybdenum, boron and nitrogen, the concentration of which in the primary ocean was extremely low.
How did they try to prove the theory?
For the first organism to appear, there must be at least one cell.
According to scientists, the appearance of the cell was facilitated by the accumulation of organic substances in the environment and the appearance of prebiotic forms – protocells, which became a connecting link between living and nonliving matter. However, these protocells are no longer on earth. But scientists know that they definitely should have contained:
self-replicating molecule with hereditary information
enclosing it from the environment
Protocell analogues were synthesized in 2011 by biologists at the University of Tokyo. As a result of the polymerase chain reaction (PCR), it was possible to achieve their full-fledged spontaneous division – similar to what happens in natural conditions.
In order to prepare the primary substrate or, in other words, coacervate, the authors of the work took dozens of organic components, the ratio of which was previously calculated on a computer. When combined, these substances formed coacervate vesicles in the substrate with a cationic sheath and DNA elements inside.
However, this was still not enough to confirm that living things can come from non-living things. DNA is not capable of self-reproduction without the participation of certain enzymes – specific proteins that catalyze all stages of its replication. Japanese scientists managed to create it in the laboratory, but, again, using biological components.
What was the material for the first life?
A new study by an international group of scientists was designed to find potential mechanisms for the formation of the first cells “from scratch” – only in the course of chemical processes, without the participation of biology.
They studied a wide range of compounds that may have formed as a result of prebiotic reactions in the early Earth.
And they found that many of these substances – ethers, amines, azides, imides, and others – under certain conditions polymerize more easily than biological compounds. And some even spontaneously create cell-like structures – compartments. According to the authors, the chains of polymers inside such compartments, twisting, could form unique three-dimensional forms – prototypes of proteins or RNA.
To obtain polymer chains in the laboratory, the authors used periodic alternation of dry and wet conditions. Evaporation of the dilute solution, as a rule, started the polymerization process, but not all of the formed polymers withstood drying. Some fell apart. Others, with the addition of water, continued the self-replicating synthesis cycle. In this, the authors see the earliest, even at the level of molecules, a manifestation of evolutionary selection, which later became an integral feature of all living organisms.
the researchers examined the polymers under a microscope and found that inside some of them there were compartments the size of a cell: they contained ten to twenty atoms. According to scientists, over time, these cell-like aggregates, after long chemical transformations, could become full-fledged cells – self-organizing structures already consisting of millions of atoms.
What was important for the birth of the first cells?
The conditions in the pond that Darwin spoke about were the basis for the origin of life, this was confirmed by research. The peculiarity of the abstract pond is that it sometimes becomes filled with water, then it dries up. That is, the cyclic alternation of wet and dry periods contributes to the appearance of complex prebiotic compounds in the chemical system, physicists also confirm.
The authors investigated polyelectrolyte coacervates in a liquid medium with the same composition as water in a pond. They simulated the conditions when the pond dries up and then refills with rainwater. And they found out: in the first case, the concentration of nucleic acids and salts increases, in the second it decreases. It does not change inside the polymer compartments.
According to the researchers, this became a key factor in the gradual formation of complex self-reproducing polymeric compounds, such as RNA, inside protocells.
Accordingly, three conditions are needed for life: