How life started

I already wrote about this subject before in 'How did life begin', but I felt it needed some additional explanations.

There are two beliefs about how life started on Earth. One is that it was created directly by God. The other is that it arose spontaneously from a biotic environment. The reason I say that these are beliefs is because neither has been proven.

Let me state that I do believe in God and that God created everything in the Universe. However, as a scientist I am curious as to how God did this amazing feat of creation. Let's say for the sake of argument that life did arise spontaneously and that this was the method that God used to create life. How was this possible?

This question is one of the most important science quests of all time. This process of life arising from organic chemicals is called 'ambiogenisis'. Scientists have been arguing about this idea for a long time. So, this means that it's a theory that needs proof.

All life is based on DNA, the complicated twin-helix molecule that allows cells to reproduce. One theory is that RNA, which is one half of DNA, arose first, perhaps in a simpler form before it eventually became RNA and then DNA. This is probably the most feasible concept, but it has to be proven. Also, RNA is incapable of passing genetic information, but it's imperative that it be shown to be the genesis of life if ambiogenesis is to be more than just a theory.

Trying to understand this complicated research problem is difficult and involves knowing about the building blocks of RNA and how they could be synthesized. I won't go into that, but I will say that RNA could have been created from a primordial soup (water and organic compounds) if the right conditions were available. This may not have been possible on Earth 4.3 billion years ago, but it may have happened in space on some other object such as a comet or an asteroid that found its way to our Earth.

The way that I think that RNA arose spontaneously is that it could have been created from simpler molecules that make it up. However, there is no known spontaneous synthesis path for pyrimidine nucleotides (the backbone units of RNA) like cytosine and uracil. The thought is that the earlier nucleic acids did not contain these nucleotides. Basically, these molecules can't exist long enough in a natural environment to sustain a biogenesis process that would lead to the RNA that life is made from.

Proposed synthesis of these nucleotides without the use of problematic cytosine and uracil has been shown, but whether these could occur in nature is not known, at least not yet. NASA has shown that the other nucleotides, adenine, guanine and related organic substances needed to synthesize RNA have been created in outer space. What this means is that these complicated molecules that make up RNA can form in stellar systems like ours.

The idea of life coming from space is called 'panspermia'. If life could be found on another planet, moon, asteroid or comet this theory would take center stage in this discussion about how life originated. The only reason this is still a theory is because the only life we know exists on Earth.

Basically, what one needs is a means of mixing certain known chemicals that existed 4.3 billion years ago in water at the correct Ph, temperature and reducing atmosphere conditions that existed back then. The problem with this idea is that we don't know the precise conditions and what precise mixture of chemicals exited then. In other words, we don't have the recipe for life formation. So far this recipe is still in the mind of God.

A current proposal is that methane, ammonia, hydrogen sulfide, carbon dioxide, carbon monoxide, phosphate, molecular oxygen, ozone and some sulfur compounds existed then. It's difficult to know what else existed then, but as time goes on these things may be revealed, especially by investigating the chemical makeup of asteroids and comets left over from the planet formation process that created Earth and the other planets in our solar system.

Now, another problem is that we need biological monomers that could become polymers. The reason why this is important is because a living cell needs these gel-like polymers to form cell walls and interior structures. Naked RNA or DNA needs a home to do its reproduction thing. This new 'biopoiesis' theory considers these processes steps in the evolution of life formation. In other words, the chemical structures of life evolved from simple molecules because of heat (geothermal) and UV (solar) radiation in steps that grew more complicated. This would suggest that these reactions created structures that couldn't lead to life, but by a process of trial and error simple bacterial life formed from the auto-synthesis of Liposome and micelle structures that had been created by primitive RNA. Even though RNA cannot cause replication of life forms it can self-replicate and catalyze the formation of chemicals needed for life, such as the synthesis of amino acids that make up almost all tissues of living things. As a matter of fact, it might suggest that viruses were the first form of life because that's what a virus is- a naked RNA strand with protein sheath around it. Maybe that's the reason that viruses are so prominent now. They've been around since the beginning of life.

The ambiogenesis theory proposes that life originated in three steps:

1. The origin of biological monomers. Molecules of amino acid could form known chemicals on Earth over a sufficiently long period. There is evidence for this.

2. The origin of biological polymers. The amino acids would form into polypeptides under the right conditions. This stage can be proven.

3. The evolution from molecules to cells. RNA gets involved with the evolution of polypeptides into cells. This idea needs work.
It's not that difficult to imagine the first two steps. It's the third step that's a stretch, at least in the current theory.

Again, I must emphasize that the idea of RNA biosynthesis is just a theory at this point, which as I've said before, means that the theory could change. Stay tuned.

Thanks for reading.