A “Universal” step may now be seen as preceding the usual “Terrestial” steps normally outlined. Below is a rough sketch of the complete account.

According to a recent article in Scientific American, (December 2000), “star dust” in intra-galactic space in our Milky Way galaxy contains various carbon compounds (including several amino acids and some polycyclic aromatic hydrocarbons, PAH) adhering to silicate grains with iron cores; the carbon compounds are sometimes dissolved in adhering water ice.

These dust particles sometimes aggregate to form comets (“dirty snowballs”, which nevertheless may contain iron and silicate cores). According to other ideas, comets may have collided with Earth (when comets were more numerous), and their water ice made the oceans on Earth. Along with the comets’ water, the organic compounds may have entered the newly created oceans.

The amino acids (and perhaps other organic compounds) were optically active enantiomers, i.e. they exhibited asymmetry (chirality). The cause of this was the circularly polarized sunlight (in general, starlight in other galactic planetary systems); itself arising from the non-conservation of CP parity (charge and mirror reflection) of the solar neutrinos arising from the asymmetry of the weak nuclear force which gives rise to the neutrinos.

The next steps on Earth would be as usual: energy input from lightning or volcanism or ultraviolet radiation tended to polymertize the amino acids to proteins, which could mutually catalyze each other to produce a primitive form of metabolism in the “protein world.

Then energy-storing molecules such as ATP (adenosine triphosphate) would polymerize to form information-storing molecules, i.e. nucleic acids – at first RNA – giving rise to the RNA world. This is usually considered to be the first stage of life, because accurate reproduction would become possible, in addition to metabolism. RNA can act as an enzyme, promoting metabolism, as well as a template, promoting reproduction. However, it appears than even proteins can reproduce themselves without the help of nuclear acids, as in the case of prions, which cause mad cow disease and its human counterpart, Creutzfeldt-Jakob disease.

The unstable RNA was then replaced in part of its function by the more stable DNA, making possible even more accurate reproduction. However, RNA continued to play important roles in protein production, as messenger RNA and carrier RNA.

So what do have as the steps to life?

1. Star dust to comets.
2. Comets to Earth oceans, with amino acids in it.
3. Polymerization of amino acids to proteins.
4. Mutual catalysis of protein proto-enzymes.
5. Coacervates (Oparin) form cell membranes.
6. Polymerization of ATP to RNA.
7. Production of DNA from RNA.
8. Prokaryotes (bacteria), first simple cells.
9. Invention of photosynthesis by blue-greens.
10 Formation of Eukaryotes.
11 Invention of sex.

Step 4 produces the protein world, imperfectly reproduced, and therefore good at producing novelty fast, but bad at hanging on to it. Mutation rate is high, but reproductive fidelity is low. Step 5 isolates the proto-life unit from the environment, and thus preserves it from re-dispersing into the medium. Steps 6 and 7 stabilize reproductive fidelity and drop innovation rate. In steps 6, 7 and 8, DNA genes are still activel swapped among individual cells, so that species are ill-defined, even among bacteria, although the networking is somewhat decreased in bacteria.

Step 10 Eukaryotes eventually invent sexual reproduction (step 11), which stabilizes species while introducing genetic variation within species. However, some Eukaryotes (fungi, mosses, ferns, higher plants) also reproduce asexually, through spores, budding, cuttings, etc. But animals never do.

I have omitted the invention of photosynthesis from the point scheme, because it deals with a different subject. Also, the chirality issues is not dealt with.