A study gives us new clues about the origin of life

In how many ways is it possible to obtain the emergence of Darwinian replicators of the type from which life originated? Are RNA and biomolecules that we know the only possibilities? Certainly not. To remind us, a new work, which demonstrates how carbon-based molecules can spontaneously give rise to replicators with their own energy "metabolism".which, if they acquire significant differences between them due to environmental causes, give rise to a competitive race for available resourceswith the final result being that leads to the selection of the most efficient type. All of this, in a system completely outside of what we call biochemistry, in a test tube environment and based on the use of relatively simple artificial molecules.

Let's be clear: evidence that Darwinian replicators could emerge spontaneously in solution, with a variety of possibilities, had already been demonstrated many times, for example using chemical environments that led to the emergence of self-replicating and competitive RNAs, able to evolve autonomously in a population variegata even containing parasites. The new work, however, shows for the first time how one of the key drivers of Darwinian evolution – the competition between populations competing for the same sources of energy – rapidly leads to the disappearance of the least efficient populationif one of the two has acquired a competitive advantagefor objects of spontaneous formation of the size of more than 1 micron (i.e. larger than the majority of known viruses), completely different and much simpler than anything we are used to thinking alive.

The researchers started from a mixture in solution of small molecules, which, irradiated with green light, in the right conditions give rise to larger compounds, or rather specific polymers, which spontaneously (as the fatty acids components of a biological membrane would do) assemble themselves into spheres of the aforementioned dimensions. These pellets contain water and some of the starting material, which has not yet reacted to form the larger compounds. As the chemical reaction triggered by the green light proceeds, the spheres become unstable, because the polymers they are made of grow again in size and because new polymers are formed inside them; eventually, an "overgrown" bead loses a portion of its constituent polymers, which will give rise to a new, smaller bead, which, if any are available, will still encapsulate some of the starting molecules to continue the cycle reproductive.

As long as there is "food" available, in the form of starting molecules and light energy, the population of spheres grows; as it becomes scarce, growth slows even more, and population size stabilizes. The growth curve of the population and its dependence on "food" perfectly reproduce those observed in populations of bacteria or protozoa, grown in the presence of a limited source of energy.

Things get interesting if there is a chemical "wild card" in the environment, or a molecule which, acting as a catalyst, is able to accelerate the "metabolism" of the spheres, increasing the speed and efficiency with which the "food" can be transformed into the constituent polymers of the spheres. Predictably, spheres incorporating this catalyst, placed in the presence of others without it, increase in number at a much greater rate, both consuming the available "food" faster and, as a result, dividing faster. Also in this case, the trend of the growth curves of the two competing populations can be superimposed on what was observed in experiments with living organisms very similar to each other, such as two species of protozoa, when one of the two has some clear competitive advantage in exploiting the available resources.

All of these results may seem like a chemist's game, but there are a few things to consider.

First: the chemistry involved in the experiment is very simple and basic indeed, of a kind that it is not impossible to imagine being in many places in the universe. Complex biochemistry is not necessary to observe this sort of self-replicating protolife with energy metabolism.

Second: rather than by replication with transmissible errors, adaptive traits can be acquired by chemical replicators at least initially directly from the environment. If this, as in many parts of the universe, is sufficiently complex from a chemical point of view, the possibility that some replicators are more suitable than others, after enlisting cofactors from outside, is clearly identifiable.

Third: the Darwinian trait referred to in the previous point, i.e. replication with transmissible error, has a clearly identifiable property at its base: a mechanism that relies on a sort of "molecular template" to generate a copy of the template itself, a subject mechanism at some controlled error rate for pure thermodynamic reasons and transmissible through the generation of altered "moulds". Well, even this characteristic is not a prerogative of the complex molecules that form life on Earth, as it can be observed in very different compounds and these too are much simpler.

In the light of these data, and considering the great availability of all that is needed (external conditions included) in every corner of the cosmos, the basis for the emergence of chemical systems with an energy metabolism and with the characteristics necessary to trigger an evolution Darwinian appears increasingly better defined, and it is not improbable that this basis will soon be reproduced in a laboratory, or found in some corner of the universe that we are probing precisely for this reason.