One of the basic properties of life is its ability to reproduce itself. Despite all the diversity we observe, at a molecular level, the reproduction of all organisms follows the same plan: a certain type of polymer - a nucleic acid - shaped like a double helix, DNA, governs the process through a 'mould' mechanism. It is precisely that, that preserves and transmits the biological information. But there is another type of nucleic acid, RNA, which is responsible for articulating the instructions contained in the DNA, such as protein synthesis.
Duplication of DNA requires the presence of proteins, but protein synthesis requires DNA. So how did DNA first appear? How do we get out of this vicious circle? The most plausible hypothesis suggests that RNA was the first carrier of genetic information. This is because it has been observed that RNA molecules have the capacity to do a double job: as primitive DNA and as protein. Thus, at an early stage, instead of the DNA-protein duo, RNA would carry out both storage and manipulation of information. This initial step is called "the RNA world".
A cosmologist has calculated the probability of life outside the Earth
How did the RNA appear? Could it have appeared by chance, by simple trial and error? What is the probability of that happening? It is believed that a viable RNA, valid for life, must have at least 40-100 nucleotides (the molecules from which both DNA and RNA are constructed). This is where the work published by Tomonori Totani in the journal Scientific Reports comes in. According to Totani, "current estimates suggest that it could not appear in the volume of space we consider the observable Universe to occupy". If the observable universe contains about 10 to 22 stars, by pure chance only one RNA of about 20 nucleotides could appear.
But Totani argues that the real universe is larger than the observable one because of inflation, a period of the rapid growth of the universe on the first shelves of its birth. From this, Totani concludes that the real universe must contain more than 10 to 100 stars "and if this is the case, more complex and life-supporting RNA structures are more than likely, they are practically inevitable.
This is not the first time a scientist has jumped into the math bandwagon to 'prove' the inevitability of life outside our planet. In 1998 the mathematician Amir C. Aczel published the book Probability 1 where making use of basic concepts of probability theory (and a series of assumptions about what the universe is like), he concludes that life is, as the biochemist and Nobel Prize winner Christian De Duve said, a cosmic imperative.
Reference: Totani, T. Emergence of life in an inflationary universe. Sci Rep 10, 1671 (2020). https://doi.org/10.1038/s41598-020-58060-0