1.b.2 – How did the transition from matter to life happen?

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December 13, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

How did the transition from matter to life happen?

The beginning of the solar system and the formation of Earth are dated back to around 4.5 billion years ago and it is estimated that it took about a billion years to gradually develop all the conditions necessary for the emergence of life.
Originally, what we today call planet Earth was a sphere of burning melted lava; this sphere was placed at a very convenient distance from the Sun: far enough so that the process of cooling and condensation could take place and at the same time close enough to prevent atmospheric gases to remain frozen.
Earth also had a size sufficient to retain a gaseous atmosphere and contained the chemical elements fundamental to the emergence of life.
After 500,000 years of gradual cooling, the steam that filled the atmosphere condensed and for thousands of years torrential rains fell on Earth and formed the oceans. During the period of cooling, carbon, the chemical element essential to life, quickly combined with hydrogen, oxygen, nitrogen, sulphur and phosphorus and generated an immense variety of chemical compounds. These six elements are still today the major chemical constituents of all living organisms.
The latest research on the origin of life are not based anymore on sudden and particular events such as an extremely powerful lightning or the insemination by molecules flown from meteorites; this research studies today the evolution of living systems as systems capable of self organization; it is then considered that the environment, formed on Earth in those bygone days, has encouraged the formation of complex molecules, that some of them became catalysts of a series of chemical reactions and that these gradually led to the formation of cell structures.
The astrophysics and geology indicate that, at that time, the appearance of Earth should have been very different from now, particularly in the chemical composition of the atmosphere and seas.
Then as now, the planet could look like a patchwork of environments, different for temperature, humidity, soil type, altitude or depth, chemical concentration of the various substances present in water or soil etc. ..
Modern biochemistry explains that in such conditions are formed molecules, called organic, which combining with each other become the bodies of living beings; furthermore, in a supportive environment, that even in remote eras could have been found somewhere on Earth, these molecules spontaneously react with each other, forming more complex compounds, accumulate and reach the right concentration for life. We must consider that these compounds are made of a large number of atoms and this leads to countless number of possible varieties; in this variety, over the millennia, it is plausible that have appeared specific molecules able to cause many chemical reactions still essential for living beings, and other molecules, known today, capable of producing copies of themselves.
Such molecules are thus able to reproduce, that means to be born by their own kind, and like all other molecules can disgregate and then die, showing therefore the main peculiarities of living beings.
There are also two other characteristics typical of living beings: a wide variety of different characters able to promote or less the reproductive process and the possibility of mutations, that is enough to start biological natural selection and evolution.
For the continuation of the history of life, a great importance had the development of two characteristics: the membranes and the use of DNA. The membranes, that still surround our cells, have a very simple basic chemical structure and were the product of one of the many above chemical reactions. These membranes form spontaneously microscopic bubbles, inside of which it is created a protected environment that maintains the right chemical concentration for the vital processes of the complex community of living molecules.
These processes, increasingly complex, began to be managed using chains of amino acids that with time, mutation after mutation, formed the DNA.
These structures, which become very complicated, had at their turn all the characteristics typical of the living beings, and they still exist today in a thousand forms and are generically called bacteria.