What is life?

First of all, it is important to understand that life is not something on its own. There is no system, matter, energy or force we can call life. The only reason we consider a system alive is because it behaves in a certain way. If there is no living system, there can be no life, since it is the behavior of the system which makes it alive. So when an organism dies, it is because its structure is altered in such a way that the behavior required for life is no longer possible, not because something is removed or leaves the system.

Life cannot be transferred from one living system to a non-living system because, for a system to behave in a certain way, it requires a specific prebuilt structure and information code which controls its behavior. If an identical copy of a system’s structure is copied in such a way that the copy starts behaving exactly like the original, then a new living system is built (a clone), life is not transferred.

Therefore, the real question here is not what life is but what does a system do to be considered alive? What is this behavior we call life? This is actually not a hard question to answer. The reason it has been difficult to answer in the past is because of our “biocentrism”, in other words, believing that features found in cellular life are what define life just because we are made of cells. But all those features have evolved with time, after the first proto-cells appeared; they are not what is really required to be alive. Let us analyze some of those features which have been considered essential for life and see if they are actually indispensable or just random evolutionary adaptations to the environment:

Metabolism: is a process by which living systems manipulate energy and resources to remain alive. Some kind of metabolism must be required for life, but also any process could work, as long as it fulfills the same main objective.

Homeostasis: is the ability of living organisms to preserve their life through internal regulatory mechanisms after the external environment threatens to change the system’s internal conditions. Homeostasis also seems to be a requirement for life because living systems have to preserve their internal environment if they want to stay alive.

Response to stimuli: is a method used by living systems to react to their changing environment when it threatens their life. As with homeostasis, organisms need to respond when their external environment changes if they want to remain alive. The difference is that homeostasis works internally while response to stimuli works externally.

Complexity: all living systems must have a certain degree of complexity, but we do not really know how complex they must be to be able to remain alive since this complexity depends on the environmental conditions disturbing the system. The harsher the environment, the harder it will be to stay alive and, as a result, complexity increases.

Reproduction: is a method used by some organisms to build one or several new separate individuals with their same structure and information code when the original organism will not be able to stay alive much longer. If an organism finds a way of not dying, it might not need to reproduce anymore, so reproduction is not essential for life. Besides, if an organism is born sterile we still consider it alive. Even a cell that can no longer divide, as long as it can metabolize and move, is still living.

Replication: is the process by which an organism creates more of the structure he is built from, to develop, grow or repair damage. It is important to make a distinction between reproduction and replication. When we grow, or a wound is healed in our body, our cells are actually replicating, not reproducing, since they are not separate organisms but part of a multicellular organism, but when bacteria divide into daughter cells, they are reproducing because a colony is not a multicellular organism. When a baby is born and it becomes a separate being, we are reproducing but if a new born human becomes part of a connected meta-organism like the Borg in Star Trek TNG, and they cannot separate from each other because they die, just like the cells in our body, then these humans will no longer be reproducing but would be replicating.

Death: is just a consequence of harsh environmental conditions and, when genetically preprogrammed, it comes as a side effect of reproduction to favor the survival of the offspring in exchange for the life of the parent. Since death is the termination of life, the purpose of life is actually to avoid death so any behavior that ends up in death is definitely a destructive behavior, not a requirement for life.

Evolution: is how a group of organisms – a species – adapts to their environment through mutations, reproduction and death. Evolution does not work at the individual level; species evolve, not organisms, but it is the organism which is alive. Furthermore, if a species stops evolving because it has reached an optimal state of adaptation to its environment, their members are not considered dead. Therefore, evolution is not a requirement for life but a consequence of death, which in turn favored reproduction as the only way to preserve life, and mutations which inserted randomness into the system to create better or worst adapting behavior.

Development: is how living systems adapt to their environment through structural change. Most organisms which reproduce also develop to be able to reach a mature state after being born. If an organism has reached, or was born with an optimal adaptation to its environment, it would not have to develop but would still be considered alive, thus, development is not a requirement for life. It is the only way, though, for an individual organism to improve its adaptation. Development can be considered, in a way, an organism’s structural evolution by means of replication instead of reproduction. It is directed, however, by the organism’s information code, which makes it more predictable than evolution.

Growth: is actually a kind of development to improve size, strength or complexity when the environment demands it. It is also the way organisms which reproduce can reach optimal adaptability or maturity after being born. Again, if a living system already has an optimal size, strength and complexity, growing is not needed to remain alive, thus, growth is not a requirement for life.

Therefore, there are two ways for an organism to adapt: by evolving (which requires mutation, reproduction and death, and only works at the species level) and by developing (which can be done at the individual level, does not require mutation, reproduction or death, works by replication and can be programmed).

The reason we associate all these features with life is because life is required in order to have these features, not because we need these features to be alive. We cannot have reproduction, replication and death if we do not already have a living system. These features came as a consequence of life, a side effect. The same with evolution and development; we need reproduction and death in order to have evolution, and we need life in order to have reproduction and death, so life is a requirement for evolution, not the other way around. Adding any of these features as part of the definition of life is arbitrary: take a living organism, see what features it has and assume they are required for life. This makes no sense, because, if we require life for these features to exist, then some kind of living system had to exist before these features were developed or evolved for the first time.

So, from this list, we can conclude that the only features that are essential for living systems to remain alive are: any number of homeostatic processes which regulate the system internally and depend on how the system behaves in the first place, some kind of metabolism to obtain the energy and resources needed to operate, but not necessarily at the chemical or molecular level (we’ll see why later), and response to stimuli which depends on the environmental forces acting on the system. If we do not take into account the environment, then we can define a closed living system as having the following two requirements to remain alive:

  • First, living systems are information systems, meaning that they have an information code which controls their behavior;
  • Second, their behavior allows them to preserve their information code.

closed-life-cycle

A Closed Living System

That’s really it! Life is a homeostatic autopoietic system and nothing else is needed, so we could say that life is just any behavior that is capable of preserving the information code which controls that same behavior. But we could also say that life is that information code which controls a behavior that is capable of preserving the information code. Then, is life the behavior or is it the information code? I believe it is the behavior, and there is a simple way to prove it: prevent the information code from preserving itself and the system dies! Even if the information code is still present, the behavior we call life is no longer there. On the other hand, alter the information code and, if the system is still capable of preserving itself, it will remain alive. Altering the information code is even required for the system to evolve but it is also not a requirement for it to be alive. So we can say that a living system requires both the information code and the behavior, but what we call life is that behavior which is capable of preserving the living system, because when the system can no longer preserve itself, it dies.

This takes us to the next feature missing from our simple closed system definition of life: the environment. Why is it that a living system needs to be able to preserve itself? We could have the information code producing some behavior and we could say that the system is alive. That is theoretically true, but the universe does not work that way. We have entropy, and the second law of thermodynamics states that any system that produces work will increase its entropy and, therefore, its energy will be dissipated in the form of heat because heat will always move from hotter regions to colder regions. So if an information code produces a behavior, this behavior will increase the system’s entropy and heat will be generated. This heat will flow out of the system making its total energy decrease. For the system to continue working, more energy has to be obtained. If the system is closed (not isolated since no system can be 100% isolated), then no energy is available and the system will end up losing all its energy and will stop working. Here is where the preservation part is needed from our definition. For systems to be alive, they need to be open systems so energy can be obtained from the environment to allow the system to continue working. For more complex systems, other resources are also needed and, once used or converted, they need to be disposed of. So an open living system must include the following:

  • First, living systems are information systems meaning that they have an information code which controls their behavior;
  • Second, they are open systems, which means that they exchange energy and resources with their environment;
  • And third, their behavior allows them to use the available energy and resources to successfully preserve their information code.

Combining these three points above, we can obtain a general definition that fits all possible life forms: A system is alive when it has an information code which controls how to exchange energy and resources from its environment in order to preserve this information code. As we can see, life turned out to be a very simple cycle: information code -> use of energy and resources (exchanged with the environment) -> preservation of information code.

opened-life-cycle

An Open Living System

So, in reality, there are only two things that the information code has to be able to do to remain alive: (1) exchange energy and resources with the environment and (2) preserve itself in such a way that the behavior continues. This definition is general enough to include all known life forms and to allow for other living systems not yet created or discovered. As long as they have an information code which controls how to preserve itself, they are alive and they will come up with new ways to remain so, or they will die.

So let’s apply this concept to cellular life on Earth, for example, a eukaryotic cell. Eukaryotic cells have a nucleus where their genetic code, made of DNA, is located. This genetic code controls how the cell works through a very complicated process which starts with the coding of RNA from DNA. This code is sent outside the nucleus where ribosomes read it and produce proteins out of amino acids obtained from the environment. These proteins will be used as resources to maintain the cell’s internal components in good health, allowing it to obtain energy and resources form the environment, get rid of waist and repair any damage produced by the environment.

cell-system

A Simplified Open Eukaryotic Cellular System

In the end, the whole purpose of all this work is to protect the DNA from being altered significantly. Metabolism, homeostasis and response to stimuli are essential, but complexity, reproduction, replication, evolution, development and growth are all simply side effects or random alterations caused by environmental forces, which could end up being helpful in maintaining the cell alive, could result in its destruction and death, or could even just be neutral to its survival. Of course, destructive behaviors vanish together with the perishing organism while helpful and neutral behaviors are preserved, adding up to the complexities we see in cellular organisms today. Sometimes even destructive behaviors survive when the organism manages to reproduce before dying and their behavior is inherited to their offspring. That is why reproduction has been such an efficient driver to evolution: behaviors that are not helpful today are still inherited and, when the environment changes, turn out to be helpful in the future. Sexual reproduction is even more efficient because the information code for non-helpful behaviors are combined and generate new behaviors that end up being helpful in the future.

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A Brief Summary of Cosmic Evolution

The universe has been evolving for roughly the last 13.7 billion years. This cosmic evolution started with a period of pure energy right after the Big Bang, until subatomic particles started to appear. According to String or M Theory, these particles where created from vibrations of multi-dimensional space-time. We do not know where these vibrations came from but it seems that the fabric of the universe vibrates in at least three dimensions of space and one dimension of time, and that these vibrations formed the first subatomic particles from which the first atoms were built, but most importantly, they gave subatomic particles certain charges which made them attract or repulse each other. Once we got attraction and repulsion, the rest is prehistory.

These simple atoms formed the first stars from which heavier elements were formed due to the pressure inside the stars. Bigger stars exploded as supernovas and formed all the rest of the heavier elements known. These explosions created lots of gases and particles called nebulas where second generation stars and, most importantly, planets formed. Since all planets, moons, asteroids and comets are also made from the rests of these nebulas, they contain lots of light and heavy elements from which molecules are produced. These molecules started combining and evolving until very complex organic molecules were created, including amino acids, lipids, RNA, proteins and, eventually, proto-cells where constructed out the combination of all these complex molecules. When DNA evolved inside some of these basic cells, many forms of bacteria and archaea flourished, and later, more complex eukaryotic cells evolved into the first multi-cellular organisms. The cells in these organisms specialized into organs and neurons from which, eventually, brains evolved. Some of these organisms with brains developed technology and here we are.

But why did this happen? Is all that came after the formation of charged subatomic particles a direct consequence of these charges or is there anything else required for life and for us to be here? Actually, nothing else is required. Living systems exist because charged subatomic particles are moving and those movements are not random but are guided by the attraction and repulsion produced by the values of those charges. Charges have a sign and particles with different sign charges attract each other while those with the same sign charges repel each other.

Subatomic particles are quarks, leptons and bosons. The most important leptons required for life are electrons, and the most important bosons (force particles) are photons and gluons. Force particles have no mass, so when they are exchanged between certain other particles with the same type of charges, only a force is produced. The Higgs boson, for example, gives mass to quarks and leptons.

Quarks and gluons possess a type of charge called “color charge” (nothing to do with their visual color but with the “signs” of their charges, which cannot be called “plus” or “minus” because they are three, so, just for convention, they are called “red”, “green” and “blue”). These color charges produce a force called the “strong nuclear force” which attracts certain types of quarks called “up” and “down” quarks with each other by exchanging gluons (the color force particle). This nuclear force is so strong that quarks cannot exist alone but have to always be joined to other quarks. When one “down” and two “up” quarks of the three different color charges are combined, they form a proton, but when one “up” and two “down” quarks of the three different color charges are joined, a neutron is formed. Nucleons (protons and neutrons) are also attracted to each other by a weaker residual nuclear force which is a secondary consequence of the color charges of quarks. When protons and neutrons are joined, the nucleus of an atom is formed by combining equal numbers of protons and neutrons, since the residual force is equal for both types of nucleons.

Subatomic particles also have another property called electric charge, which can be positive (+) or negative (-). Particles with different signs attract each other while those with the same signs repel each other with a force called the electromagnetic force. “Up” quarks have an electric charge of 2/3, “down” quarks have a -1/3 charge and electrons have a -1 electric charge. This means that a proton will have a sum of +1 (2/3 + 2/3 – 1/3 = 1) and neutrons will sum up to 0 (2/3 – 1/3 – 1/3 = 0). When the atomic nucleus is formed from the combination of protons and neutrons, it will add up to a positive electric charge which equals the sum of all the protons in it (considering that neutrons do not contribute any electric charge). Depending on the number of protons in the nucleus, the same number of negatively charged electrons will be electrically attracted to it, and thus atoms are formed. The electromagnetic force is produced when photons (particles of light) are exchanged between positively charged protons and negatively charged electrons. Since this force is not as strong as the strong nuclear force, the electron will orbit the nucleus at a certain distance which depends on the number of protons and electrons present in the atom. While the nuclear forces can act only at very short distances inside the nucleus, the electromagnetic force has an infinite range, but becomes weaker as distances between particles increase.

There is a third force which also acts on subatomic nuclear particles. It is even weaker than the electromagnetic force and is related to the decay of neutrons into protons by emitting an electron. The force is mediated by the exchange of other force particles called W and Z bosons. With the addition of energy, a proton can turn back into a neutron by absorbing an electron. This is not directly related to the creation of life, since it does not normally happen under natural conditions but is important in understanding the origin of new subatomic particles from existing ones and the existence of radiation.

Finally, there is a fourth force which acts on all particles. It is called gravity and, even though it is by far the weakest of all forces, it also has an infinite range like the electromagnetic force, but it always adds up, meaning that it is positive. The more particles that come together, the greater their gravitational force becomes. Gravity depends on the mass property of the particles involved so its force is negligible at the subatomic level but becomes important for combinations of billions of particles into more massive objects. Gravity is important in the creation of life since it acts as an environmental variable affecting the adaptation of organisms. It is believed that another force particle, the graviton, is exchanged when objects with mass are attracted by their gravity but this has not yet been confirmed. There is also a negative gravity (called dark energy) that fills the intergalactic space in the universe where there are no mass particles, but its origin is unknown. In any case, it is not a property of known particles even though it does repel particles with mass causing the accelerated expansion of the universe.

Once atoms join together to create molecules, the only two forces still acting are gravity and electromagnetism. Nuclear forces are no longer an issue. Molecules are formed by chemical bonds and other weaker attractions related to residual electromagnetic charges. A chemical bond is created when two or more atoms share or transfer electrons holding the atoms together. Atoms of the same type form elements while atoms of different types join to form compounds. Large molecules are made of many different organic compounds, including amino acids, proteins, lipids, RNA and DNA, from which cells are made. Eukaryotic cells form multi-cellular organisms and specialize into organ tissue, including neurons from which brains are formed. Finally, some of these organisms with brains are capable of developing technology, but still, the same four forces are all that’s needed, combining the same basic elements. In other words, there is no difference between cells and molecules, they are all made of the same stuff, and the only difference is how they are organized.

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Introduction to my Theory on Cosmic Evolution and Life

Cosmic evolution is not a simple accumulation of smaller parts which are just getting more complex and bigger. Distinct stages can be identified, which share common structures and, when these structures evolve into something totally new, the next stage emerges. When we talk about Physics, Chemistry, Biology and Technology, we are, in a certain way, acknowledging the different stages in the evolution of the universe but, in my opinion, with a very simplistic and anthropocentric view. For the last ten years I have been developing a Theory on the Evolutionary Stages of the Universe that can better define how these stages are divided by first understanding what life really is and how it evolves from the point of view of systems theory. In the next posts, I will be developing my theory further, first by explaining what I believe is life and then how each stage in the evolution of the universe has emerged from this basic definition of life.

opened-life-cycleApart from giving a very detailed explanation on how the universe evolved and should continue evolving, I believe this theory has huge implications on the definition of life, why I think life is autopoietic and why it has been so hard to draw a line between living and non-living systems.

How can a non-living structure evolve into a living organism? Isn’t life a requirement for evolution? Maybe cellular organisms are just more complex living systems but life, in its basic autopoietic form, has always been present, only at a simpler stage. I believe the concept of life used in Biology is anthropocentric, arbitrary and only useful taxonomically. Instead of defining first what the basic requirement for being alive is and then finding out which systems fulfill this requirement, Biologists have worked it backwards by first establishing arbitrarily which organisms are alive and which are not and then assuming that life is whatever features these organisms have. That is a taxonomical definitions but not a systems theory definition. In the end, system theorists have been forced to include all those features into their living systems just to please a taxonomical definition. It would be just as possible to assume that only animals are alive and then forcing the definition of life to be systems with a neural network just because it is what separates animals from plants. This is also what has been done with the definition of intelligence. That is why we still don’t have a logical definition of life from a Biological point of view because the system has to fit a definition which is arbitrary and includes features which have evolved randomly in this planet: whatever features cellular life on Earth has, they have to be included into the definitions of a living system without even knowing what being alive really is. I believe we have to start thinking the other way around: see first what life really is and then find out which systems in the universe (not just Earth) include this feature. It has to be just one feature, not a bunch of randomly evolved features. The same with intelligence, once we really understand what it is to be intelligent, we will be able to determine which systems in the universe have intelligence. We will realize, in the same way as with life, that intelligence is present in all evolutionary stages of the universe but in a simpler form.

Exobiologists could also use this theory to understand better how living systems could have evolved in other planets. Maybe cellular life is just one possibility out of many other forms of evolution from molecules. If we understand that sub-atomic particles are capable of evolving into molecules that have adapted to our planet, maybe sub-atomic particles can evolve differently in other planets, and create very different molecules and polymers which will then evolve into some other life form different from our planet’s cellular evolution. Maybe we do not need water or carbon if we can think of polymers that can survive in very different conditions.

Another implication for this theory has to do with future evolution, or evolution beyond our multi-cellular organisms and how this will affect climate change. Maybe every evolutionary level modified the planet’s climate in unforeseen ways which were unfavorable to their living conditions but this change was necessary for evolution to kick-in and adapt so a new evolutionary level was created. Suppose cyanobacteria did not convert our planet’s atmosphere into an oxygen rich one, would animal life forms had evolved? Maybe those cyanobacteria are not capable of evolving into animals and only into plants. Maybe other life forms which were adapted to living in a CO2 rich atmosphere would have evolved into very different kinds of animals, but maybe not. Is our current climate change a similar transformation required for us to evolve into the next level, which I call meta-organisms?

Is a society or a city the next level of evolution? I don’t think it is, just like the next level of evolution of bacteria is not a colony but a multi-cellular organism. By extrapolating the way the universe has evolved from energy to subatomic particles and then to molecules, cells and multi-cellular organisms, we can see that the next evolutionary level is not a society or a colony of humans but a very different kind of meta-organism which has not yet evolved. Just like the first molecules had to evolve into complex polymers in order to form the structures needed for the first cells to evolve, and just like the first simple cells had to evolve into eukaryotic cells to form the first multi-cellular structures from which plants and animals evolved, humans need to evolve into something much more complex and advanced before the first structures needed to form meta-organisms evolve.

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