The origin of life



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Often I hear people ask: how is it possible that to a certain point a combination of organic and inorganic molecules has developed life? How cannot all this be attributed to the intervention of some superior entity, a creator god? In fact when we look at a cat and a piece of rock, it is quite difficult to imagine how in the end they are both made of atoms and molecules, although combined in different ways. The same if you look at a flower or a crystal of quartz. Of course, a living being is immensely more complex than a crystal, the organic molecules it is made of, are often very complicated and generally have the ability to perform very articulated operations. Just think to certain enzymes or how proteins activate or inactivate specific genes in our DNA.

The point is, how did this step occur? How is possible that it happened without outside intervention?

I have thought a lot about this question and finally I realized that it is flawed, that is, it assumes that during the transition from a set of molecules to a living being there must have been a substantial, significant, determinant change. This assumption stems from the fact that when we think of a non-living system, it comes to our mind stones, objects, relatively simple structures or, in any case systems that can be decomposable into simple substructures. On the other hand, one of the essential characteristics of life is the difficulty to consider a subsystem of a living being as a living entity itself.

It is not enough that a being be composed of organic matter to live: when we think about life we almost always refer to a complex system that cannot be broken down into parts that could exist independently. An arm, a liver, a piece of skin, do not live particularly long if detached from the main body, even if in fact there are cases, such as planarias or hydro, where a piece of body can give rise to a new whole organism. But the point here is not what life is but how we perceive it, or better, the fact that we take life a different value than the inorganic material and then that we find difficult to conceive how the latter can become the former.

Similarly, it is true that there are clusters of living beings that can be separated, such as films of bacteria, colonies of coral, some jellyfish, and symbiotic systems such as lichens, but even in these cases we make a single breakdown and still find ourselves with examples of what we call life, pre-aggregated for convenience or mere survival.

But then, why the original question is wrong or better, has in itself the reason why it seems so difficult to give it an answer? To prove it, as it may seem absurd, we do not really need to define what life is and in fact we will not, even if we will use a meta-definition.

The experiment of marbles

We can say that a being is said to be living when it has certain characteristics. For the purposes of this article, however, is not important which they are but simply that they are definable and that they are limited in number. So we say that a system is alive if it has N characteristics and we designate them with the symbols V1, V2, V3, … VN. Now imagine a world in which the elements bind together to form more complex molecules of every possible shape and composition. These molecules in turn will bind to form structures of various types that interact with the external environment in various ways. Taken any of these systems, we could say that it has certain characteristics which we will designate as S1, S2, S3, … SM, where M is a number that may vary structure by structure.

At this point, given enough time and a fairly large number of structures, we may say that some of them may begin to have some of the features that we associate with life, such as V3 or V7. At the beginning some of these features may appear alone, but with the passage of time and being the structures more and more complicated, we will have systems that present two or more of these characteristics, until there comes a point where a structure will show all of them but one, say VN, since the number is irrelevant. At this point what will happen when the last piece will be left in its place? We’ll have the life, of course, but can we conclude that this event was more significant than the positioning of the previous pieces?

This development is quite easy to prove and does not need a supercomputer to do it, but just some colorful marbles. Suppose, for simplicity, that N is 10. Nothing would change if it were 20, 100 or 1,000, except that it would take more time to do the experiment. Let us take one hundred white marbles and begin to number them from 1 to 10, in order to have ten marbles with the number 1, ten with the number 2 and so on. Let us place them in a case. Then let us put in the same case a few thousand marbles of different colors. Let’s say one hundred of red ones, two hundreds of blue ones, five hundreds of yellow ones and so on. We have not to number them too, anyway.

When done, let us mix all of them very well and begin to take from the case groups of three marbles. We could take groups of a variable number of marbles or start with two at a time or with five: even in such cases it would make no difference but increasing the time needed to make the experiment. So, let us take the three marbles and join them. For example, if the balls were drilled we could bind them together, or we could put them in a small bag. Once done, let us put each group in a second case. At the end of this first phase we have a case full of triplets of marbles. Some of these triplets may have one, two or even three white marbles inside them. Obviously none of these triplets have 10 white marbles, each one with a different number.

Let us go ahead. Let us mix the triplets in the case and take three of them, join them as we did before to create nineplets. Then let us put each nineplet in the previous case, the one that we had filled at the beginning with the single marbles. The result will be a case of nineplets, or groups of nine marbles. Also in this case it will be very difficult that all the marbles of a nineplet be white and have all different numbers, but basically we have executed only two steps. I believe it is clear now how to proceed. Continuing to build increasingly complex structures, namely groups of 27 marbles, then 81 and so on, sooner or later — it’s just a matter of time — we will begin to find clusters with ten or more white marbles. Obviously a lot of white marbles will be duplicated, but it is quite easy to show how at one point we will extract a group that will contain at least ten white marbles with over the first ten natural numbers. Just remind that, even if we might be unlucky in fishing, sooner or later, with that mechanism, we would create a structure that would contain all the original balls of the box and then, as it was initially filled, all ten groups of ten white marbles.

From non-life to life

Our planet has had much more than a few thousand marbles to play with and hundreds of millions of years to do it. Whatever be the set of characteristics that we associate with life, it was only a matter of time for increasingly complex structures featuring them. Just imagine that moment: on the planet there are now millions of complex molecular structures, each one with one, two, up to N-1 characteristics among those ones that we associate with life. So none of these structures can be called living, but at a certain moment another combination occurs that leads to form a structure that also has the VN characteristic, the last one. In fact, that event must have happened many times and not always the missing feature was the same. Also, the life thus formed probably extincted many times or failed to take root, but the planet has continued his chemical mixing, insensitive to failures, unabashed in its becoming.

So now the transition from non-life to life no longer has the charm of mystery which certainly makes it very appealing to our minds, but it is simply the latest step in a series of combinations that have been repeated for millions of years. For us, this step is crucial, of course, because otherwise we would not be here to discuss, but can we say that it is the last ring added to the chain to be important, or rather it is the set of all rings to form the chain? At this point it is evident that it is irrelevant to this discussion which or how many could be the characteristics that define life for us. Any set you had to choose, the transition from a non-living system to a living one is just a matter of conventions. It has nothing momentous in itself, no more than placing the last tile of the roof on top of a house to be able to say that yes, that is really a house now.

Some billions of years ago our planet was formed and life was very different from what exists today on Earth. That life was swept away completely only to reappear in another form. Subsequent extinctions have reshaped the biosphere of our planet and probably it will happen again. In whatever way we are defining life, it has the same origin as the inorganic material, i.e. everything was born from the stars that produced all the elements up to iron, and from supernovae, which have created the heaviest ones, essential to more complex living being. The same probably happened and is happening today in many other star systems and exoplanets. Life is probably much more common than we thought at one time and it is only the latest stage of a process that began almost 14 billion years ago and will last for many billions more.

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