Understanding the nature of life is one of the most difficult and at the same time interesting mysteries for mankind. Over time, this mystery inevitably went beyond the question of whether there is life only on Earth, or whether it exists somewhere else in the universe. Is the emergence of life an accidental and fortunate coincidence of circumstances, or is it as natural to the Universe as the universal laws of physics?
Scientists have long been trying to answer these questions. One of them is Jeremy Ingland, a biophysicist at the Massachusetts Institute of Technology. In 2013, he hypothesized that the laws of physics could become a trigger for chemical reactions that allowed simple substances to be organized in such a way that they eventually acquired "vital" qualities.
In the results of a new work by Ingland and his colleagues, it is noted that physics can naturally create processes of self-producing reactions, which is one of the first steps to creating a "living" from the "lifeless". In other words, this means that life is directly derived from the fundamental laws of nature, which virtually excludes the possibility of a hypothesis about accidental occurrence. But that would be too loud a statement.
Life had to come from something. Biology did not always exist. It also appeared as a result of a chain of certain chemical processes that led to the fact that the chemicals somehow organized into prebiotic compounds, created the "building blocks of life", and then turned into microbes that eventually developed into an amazing set of living things, existing today on our planet.
The theory of abiogenesis considers the emergence of life as the emergence of living nature from the inanimate and, according to Ingland, the basis and key, through which non-living chemical compounds could turn into living biological may be thermodynamics. However, as the scientist himself notes, the recent research does not set a goal in creating a connection between the "vital properties" of physical systems and biological processes.
"I would not say that I conducted a work that could answer the question of the very nature of life as such," Ingland told Live Science.
"What I was interested in is the very proof of the principle – what are the physical requirements for manifestation in lifeless compounds of living behavior."
Self-organization in physical systems
When energy is applied to the system, the laws of physics dictate how this energy will dissipate. If an external source of heat acts on this system, then the energy begins to dissipate until thermal equilibrium is organized around this system. Put a hot cup of coffee on the table and in time the place where the cup was standing will become warm. However, some physical systems can be nonequilibrium, therefore through "self-organization" they try to use the energy of an external source in the most effective way, as a result of which self-sustaining chemical reactions, which prevent achieving thermodynamic equilibrium, are triggered quite interesting, according to Ingland. It's as if a cup of coffee spontaneously provoked a chemical reaction that made it hot to keep only a tiny area of coffee in the center of the cup, preventing it from cooling and transitioning to thermodynamic balance with the table. The scientist calls such a situation "adaptation to dissipation," and this mechanism is precisely what gives inlang non-living physical systems living properties.
The key behavior of life is the possibility of self-reproduction or (from a biological point of view) reproduction. This is the basis for any life: it is read as the simplest, then reproduced, becomes more and more complex, then again reproduced and this process is repeated again and again. And it so happened that self-replication is also a very effective way of dissipating heat and increasing entropy within this system.
In a study published July 18 in the Proceedings of the National Academy of Sciences, Ingland and co-author Jordan Horowitz describe testing their hypothesis. They conducted several computer simulations of a closed system (a system that does not exchange heat or matter with its environment) containing a "soup" of 25 chemicals. Despite the fact that their system was very simple, it was this "broth" that could have once covered the surface of an ancient and lifeless Earth. So it turned out that if these chemicals are together and they are exposed to heat from an external source (for example, a hydrothermal well), then these substances will somehow have to dissipate this heat according to the second law of thermodynamics, which says that heat must dissipate and the entropy of the system at this moment will inevitably increase.
When creating certain initial conditions, the scientist discovered that these chemicals can optimize the effect exerted on the energy system by self-organization and subsequent active reactions for self-replication. These chemicals naturally naturally adjusted to the changed conditions. The reactions created by them also produced heat, which corresponds to the second law of thermodynamics. Entropy in the system will always increase and chemicals will also continue to self-organize and demonstrate life behavior in the form of self-reproduction.
"In fact, the system first tries a lot of small scale solutions and when one of them starts to show a positive result, the organization of the entire system and adjustment for this decision does not take much time," Ingland told Live Science.
A simple model of biology looks like this: molecular energy burns in cells that are inherently out of balance and control metabolic processes that support life. But as Ingland points out, there is a big difference between the revealed vital properties and behavior in a virtual chemical soup and life itself
Sarah Imari Walker, the theoretical physicist and astrobiologist at the University of Arizona, agrees with this, did not take part in the studies under discussion today.
"There are two ways that you need to go through to try and combine biology and physics. One is to understand how you can get life quality from simple physical systems. The second is to understand how physics can create life. It is necessary to solve both these conditions in order to really understand what properties are really unique for life as such and what properties and features are characteristic of things that you can take for living systems, for example prebiotics, "commented Imari Walker of Live Science.
The origin of life outside the Earth
Before we begin to answer the big question about whether these simple physical systems can influence the appearance of life elsewhere in the universe, it is first necessary to better understand where such systems can exist on Earth.
"If by the word" life "you mean something that is as impressive as say bacteria or any other form with polymerases (proteins that connect DNA and RNA) and DNA, then my work does not mean that, how easy or difficult it is to create something so complex, so I would not like to try to guess ahead of time whether we'll find something like this anywhere in the universe, except the Earth, "says England.
This study does not determine how biology originated from non-biological systems, it is only aimed at explaining some of the complex chemical processes that are responsible for the self-organization of chemicals. Carried out computer simulations do not take into account other vital properties, such as adaptation to the environment or reaction to external stimuli. In addition, this thermodynamic study of a closed system does not take into account the role of the transfer of accumulated information, notes Michael Lassing, a statistical physicist who also studies quantitative biology at the University of Cologne.
"This work certainly shows an amazing result of the interaction of nonequilibrium chemical networks, but we are still far from when physics can explain the nature of life in which one of the key roles is devoted to the reproduction and transfer of information," commented Lassing Live Science .
The role of information and its transfer in living systems is very important, agrees Imari Walker. In her opinion, the presence of natural self-organization present in the "soup" of chemicals does not necessarily mean that it is a living organization.
"I believe that there are many intermediate steps that we need to go through to move from simple ordering to creating a fully functional information architecture like living cells, which requires the presence of something like memory or heredity. We can certainly get order in physics and non-equilibrium systems, but that does not mean that we will get a life like this, "said Imari Walker.
Experts generally believe that it is likely to be premature to say that Ingland's work is "a convincing proof" of the nature of life, since there are many other hypotheses trying to describe how life could have formed from almost nothing. But it is definitely a fresh look at how physical systems are able to self-organize themselves in nature. Now that scientists have a general idea of how this thermodynamic system behaves, perhaps the next step will be an attempt to determine a sufficient number of nonequilibrium physical systems appearing on the Earth, says Ingland.