We still don’t know how, where and why life first appeared on our planet. Part of the challenge is that there is no clear, universally accepted definition of “life.”

Since the vast majority of living things are absolutely living, and only viruses, prions, etc. This is usually not a problem, since biologists interested in extremes such as need not worry about precise classifications. But to study the origin of life, we must necessarily examine a process that takes inanimate matter and fundamentally changes it. Presumably this process occurred in stages, in leaps and bounds, so the line between uncoordinated chemical reactions and the onset of vibration must be blurred.

Here, instead of rewriting biology textbooks, it would be useful to at least give a simple and useful definition of life; so we can at least frame the debate about the origin of life correctly. And for these purposes, a simple explanation will suffice: Life is something subject to Darwinian evolution. That is, life experiences natural selection, the constant pressure that selects traits and characteristics that will be passed on to new generations for the simple virtue of their survival. A trait is protected if it contributes in a specific way, even indirectly, to the survival and reproductive ability of the organism. Everything else is thrown away (or at best, unceremoniously taken along for the ride).

Earth is the only known place in the solar system, the galaxy, and the entire universe where Darwinian evolution occurred.

To succeed in evolution and separate itself from simple chemical reactions, life must do three things. First, it must somehow store information, such as coding regarding various processes, features, and characteristics. In this way successful qualities can be passed on from one generation to the next.

Second, life must reproduce itself. It must be able to make sufficiently accurate copies of its own molecular structure that the information it contains has a chance of becoming a new generation, modified and modified depending on its survival. Finally, life must catalyze reactions. It has to influence its environment, whether for movement, for obtaining or storing energy, for the creation of new structures, or for the many wonderful activities that life carries out every day.

Life can evolve by interacting with the environment, making copies of itself and storing information (such as how to interact with the environment and replicate itself), becoming more complex and specialized over geological time, evolving from humble molecules into conscious minds. to their own secret origins.

In the modern era, through billions of years of practice, life on Earth has developed a dizzying array of chemical and molecular machines for self-reproduction; It’s a zoo so complex and interconnected that we don’t yet fully understand it. But the real picture emerged. To put it extremely simply (because I don’t want you to confuse me with a biologist), life accomplishes these tasks through a trio of molecular tools.

One of these is DNA, which stores information through its genetic code using combinations of only four molecules: adenine, guanine, cytosine and thymine. DNA’s ability to store vast amounts of information is nothing short of a miracle; Our own system of digital ones and zeros (invented because it is much easier to tell whether a circuit is open or closed than an intermediate stage) is the closest comparison we can make to the information density of DNA. Natural languages ​​aren’t even on the list.

The second component is RNA, which is curiously similar to DNA but has two subtle but important differences: RNA substitutes uracil for thymine in the coding base and contains the sugar ribose, which is one oxygen atom less than DNA’s deoxyribose. RNA also stores information, but again only in a general sense, it does the basic work of reading the chemical instructions stored in DNA and using them to produce proteins, the final member of the trio.

“Proteins” is a general term for a nearly countless variety of molecular machines that do things: They cut molecules, bond them together, make new ones, hold structures together, become structures themselves, move important molecules from place to place. converting energy from one form to another, etc.

Proteins have another function: They do the job of unwinding DNA and making copies of it. Thus, the trinity performs all the functions of life: DNA stores information, RNA uses this information to produce proteins, and proteins interact with the environment to carry out the self-replication of DNA. This cycle allows living organisms to experience the gift of evolution.

And this cycle, as I said, is incredibly complex and is clearly the result of billions of years of fine-tuning and refinement. The interconnected nature of DNA, RNA and proteins means that they could not have emerged from primordial mud from the outset; because if a single component is missing, the whole system collapses; A table with three legs and one without one cannot stand.